HOLTEK HT66F0172

Enhanced A/D Flash 8-Bit MCU
HT66F0172/HT66F0174
Revision: V1.00
Date: �������������
July 11, 2013
HT66F0172/HT66F0174
Enhanced A/D Flash 8-Bit MCU
Table of Contents
Features............................................................................................................. 6
CPU Features.......................................................................................................................... 6
Peripheral Features.................................................................................................................. 6
General Description ......................................................................................... 7
Selection Table.................................................................................................. 7
Block Diagram................................................................................................... 8
Pin Assignment................................................................................................. 8
Pin Descriptions............................................................................................... 9
Absolute Maximum Ratings............................................................................11
D.C. Characteristics.........................................................................................11
A.C. Characteristics........................................................................................ 13
A/D Converter Characteristics....................................................................... 14
LVD&LVR Electrical Characteristics............................................................. 15
Power on Reset Electrical Characteristics................................................... 15
System Architecture....................................................................................... 16
Clocking and Pipelining.......................................................................................................... 16
Program Counter.................................................................................................................... 17
Stack...................................................................................................................................... 18
Arithmetic and Logic Unit – ALU............................................................................................ 18
Flash Program Memory.................................................................................. 19
Structure................................................................................................................................. 19
Special Vectors...................................................................................................................... 19
Look-up Table......................................................................................................................... 19
Table Program Example......................................................................................................... 20
In Circuit Programming.......................................................................................................... 21
On-Chip Debug Support – OCDS.......................................................................................... 22
RAM Data Memory.......................................................................................... 22
Structure................................................................................................................................. 22
Special Function Register Description......................................................... 24
Indirect Addressing Registers – IAR0, IAR1.......................................................................... 24
Memory Pointers – MP0, MP1............................................................................................... 24
Bank Pointer – BP.................................................................................................................. 25
Accumulator – ACC................................................................................................................ 25
Program Counter Low Register – PCL................................................................................... 25
Look-up Table Registers – TBLP, TBHP, TBLH...................................................................... 25
Status Register – STATUS..................................................................................................... 26
Rev. 1.00
2
July 11, 2013
HT66F0172/HT66F0174
Enhanced A/D Flash 8-Bit MCU
EEPROM Data Memory (only for HT66F0174).............................................. 28
EEPROM Data Memory Structure......................................................................................... 28
EEPROM Registers............................................................................................................... 28
Reading Data from the EEPROM ......................................................................................... 30
Writing Data to the EEPROM................................................................................................. 30
Write Protection...................................................................................................................... 30
EEPROM Interrupt................................................................................................................. 30
Programming Considerations................................................................................................. 31
Oscillator......................................................................................................... 32
Oscillator Overview................................................................................................................ 32
System Clock Configurations................................................................................................. 32
External Crystal/Ceramic Oscillator – HXT............................................................................ 33
Internal RC Oscillator – HIRC................................................................................................ 34
External 32.768kHz Crystal Oscillator – LXT......................................................................... 34
LXT Oscillator Low Power Function....................................................................................... 35
Internal 32kHz Oscillator – LIRC............................................................................................ 35
Supplementary Clocks........................................................................................................... 35
Operating Modes and System Clocks.......................................................... 36
System Clocks....................................................................................................................... 36
System Operation Modes....................................................................................................... 37
Control Register..................................................................................................................... 38
Fast Wake-up......................................................................................................................... 40
Operating Mode Switching .................................................................................................... 40
NORMAL Mode to SLOW Mode Switching............................................................................ 41
SLOW Mode to NORMAL Mode Switching ........................................................................... 41
Entering the SLEEP0 Mode................................................................................................... 43
Entering the SLEEP1 Mode................................................................................................... 43
Entering the IDLE0 Mode....................................................................................................... 43
Entering the IDLE1 Mode....................................................................................................... 44
Standby Current Considerations............................................................................................ 44
Wake-up................................................................................................................................ 45
Programming Considerations................................................................................................. 45
Watchdog Timer.............................................................................................. 46
Watchdog Timer Clock Source............................................................................................... 46
Watchdog Timer Control Register.......................................................................................... 46
Watchdog Timer Operation.................................................................................................... 47
Reset and Initialisation................................................................................... 48
Reset Functions..................................................................................................................... 48
Reset Initial Conditions.......................................................................................................... 51
Rev. 1.00
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July 11, 2013
HT66F0172/HT66F0174
Enhanced A/D Flash 8-Bit MCU
Input/Output Ports.......................................................................................... 53
Pull-high Resistors................................................................................................................. 53
Port A Wake-up...................................................................................................................... 54
I/O Port Control Registers...................................................................................................... 55
I/O Pin Structures................................................................................................................... 56
Programming Considerations................................................................................................. 57
Timer Modules – TM....................................................................................... 58
Introduction............................................................................................................................ 58
TM Operation......................................................................................................................... 58
TM Clock Source.................................................................................................................... 58
TM Interrupts.......................................................................................................................... 59
TM External Pins.................................................................................................................... 59
TM Input/Output Pin Control Registers.................................................................................. 59
Programming Considerations................................................................................................. 60
Periodic Type TM – PTM................................................................................. 61
Periodic TM Operation........................................................................................................... 61
Periodic Type TM Register Description.................................................................................. 62
Periodic Type TM Operating Modes....................................................................................... 66
Compare Match Output Mode................................................................................................ 66
Timer/Counter Mode.............................................................................................................. 69
PWM Output Mode................................................................................................................. 69
Single Pulse Mode................................................................................................................. 70
Capture Input Mode............................................................................................................... 71
Analog to Digital Converter........................................................................... 73
A/D Overview......................................................................................................................... 73
A/D Converter Register Description....................................................................................... 73
A/D Converter Data Registers – ADRL, ADRH...................................................................... 74
A/D Converter Control Registers – ADCR0, ADCR1, ACERL................................................ 74
A/D Operation........................................................................................................................ 77
A/D Input Pins........................................................................................................................ 78
Summary of A/D Conversion Steps........................................................................................ 79
Programming Considerations................................................................................................. 80
A/D Transfer Function............................................................................................................ 80
A/D Programming Examples.................................................................................................. 81
Rev. 1.00
4
July 11, 2013
HT66F0172/HT66F0174
Enhanced A/D Flash 8-Bit MCU
Interrupts......................................................................................................... 83
Interrupt Registers.................................................................................................................. 83
Interrupt Operation................................................................................................................. 88
External Interrupt ................................................................................................................... 89
Time Base Interrupt................................................................................................................ 90
Multi-function Interrupt........................................................................................................... 91
A/D Converter Interrupt.......................................................................................................... 92
TM Interrupt............................................................................................................................ 92
EEPROM Interrupt (Only for HT66F0172)............................................................................. 92
LVD Interrupt.......................................................................................................................... 92
Interrupt Wake-up Function................................................................................................... 93
Programming Considerations................................................................................................. 93
Low Voltage Detector – LVD.......................................................................... 94
LVD Register.......................................................................................................................... 94
LVD Operation........................................................................................................................ 95
Configuration Option...................................................................................... 96
Application Circuits........................................................................................ 96
Instruction Set................................................................................................. 97
Introduction............................................................................................................................ 97
Instruction Timing................................................................................................................... 97
Moving and Transferring Data................................................................................................ 97
Arithmetic Operations............................................................................................................. 97
Logical and Rotate Operation................................................................................................ 98
Branches and Control Transfer.............................................................................................. 98
Bit Operations........................................................................................................................ 98
Table Read Operations.......................................................................................................... 98
Other Operations.................................................................................................................... 98
Instruction Set Summary........................................................................................................ 99
Instruction Definition.................................................................................... 101
Package Information.....................................................................................110
20-pin DIP (300mil) Outline Dimensions...............................................................................111
20-pin SOP (300mil) Outline Dimensions.............................................................................113
20-pin SSOP (150mil) Outline Dimensions...........................................................................114
Rev. 1.00
5
July 11, 2013
HT66F0172/HT66F0174
Enhanced A/D Flash 8-Bit MCU
Features
CPU Features
• Operating Voltage:
fSYS = 8MHz: 2.2V~5.5V
fSYS = 12MHz: 2.7V~5.5V
fSYS = 20MHz: 4.5V~5.5V
• Up to 0.2μs instruction cycle with 20MHz system clock at VDD=5V
• Power down and wake-up functions to reduce power consumption
• Four oscillators:
External Crystal – HXT
External 32.768kHz Crystal- LXT (only for HT66F0174)
Internal RC – HIRC
Internal 32kHz – LIRC
• Multi-mode operation: NORMAL, SLOW, IDLE and SLEEP
• Fully integrated internal 8MHz oscillator requires no external components
• All instructions executed in one or two instruction cycles
• Table read instructions
• 63 powerful instructions
• 8-level subroutine nesting
• Bit manipulation instruction
Peripheral Features
• Flash Program Memory: 2K×16
• RAM Data Memory: 128×8
• EEPROM Memory: 64×8 (only for HT66F0174)
• Watchdog Timer function
• 18 bidirectional I/O lines
• Two pin-shared external interrupts
• Two 10-bit PTM
• Dual Time-Base function for generation of fixed time interrupt signal
• 8-channel 12-bit resolution A/D converter
• Low voltage reset function
• Low voltage detect function
• Package types: 20-pin DIP/SOP/SSOP
Rev. 1.00
6
July 11, 2013
HT66F0172/HT66F0174
Enhanced A/D Flash 8-Bit MCU
General Description
The devices are Flash Memory type 8-bit high performance RISC architecture microcontrollers.
Offering users the convenience of Flash Memory multi-programming features, these devices also
include a wide range of functions and features. Other memory includes an area of RAM Data
Memory as well as an area of EEPROM memory for storage of non-volatile data such as serial
numbers, calibration data etc.
Analog features include a multi-channel 12-bit A/D converter function. Extremely flexible Timer
Modules provide timing, pulse generation and PWM generation functions. Protective features such
as an internal Watchdog Timer, Low Voltage Reset and Low Voltage Detector coupled with excellent
noise immunity and ESD protection ensure that reliable operation is maintained in hostile electrical
environments.
A full choice of HXT, LXT, HIRC and LIRC oscillator functions are provided including a fully
integrated system oscillator which requires no external components for its implementation. The
ability to operate and switch dynamically between a range of operating modes using different
clock sources gives users the ability to optimise microcontroller operation and minimize power
consumption.
The inclusion of flexible I/O programming features, Time-Base functions along with many other
features ensure that the devices will find excellent use in applications such as electronic metering,
environmental monitoring, handheld instruments, household appliances, electronically controlled
tools, motor driving in addition to many others.
Selection Table
Most features are common to all devices. the following table summarises the main features of each device.
Part No.
Oscillator
ROM
RAM
HT66F0174 2.2V~ 5.5V
HXT
HIRC
LIRC
LXT
2K×16
128×8
64×8
HT66F0172 2.2V~ 5.5V
HXT
HIRC
LIRC
2K×16
128×8
—
Rev. 1.00
VDD
Ext.
Int.
A/D
Stack
Time
base
comparator
Package
18
2
12-bit×8
8
√
√
20DIP/
SOP/SSOP
18
2
12-bit×8
8
√
√
20DIP/
SOP/SSOP
EEPROM I/O
7
July 11, 2013
HT66F0172/HT66F0174
Enhanced A/D Flash 8-Bit MCU
Block Diagram
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„ Note: There are not LXT oscillator and EEPROM in HT66F0172.
Pin Assignment
VSS&AVSS
1
�0
VDD&AVDD
PC0/OSC1
�
19
PB0/INT0/AN0/XT1
PC1/OSC�
�
18
PB1/INT1/AN1/XT�
PB�/TCK0/AN�
PC�
4
17
PA0/TP0/ICPDA/OCDSDA
5
16
PA4/TCK1/AN�
PA1
6
15
PA5/AN4/VREF
PA�/ICPCK/OCDSCK
7
14
PA6/AN5
PA7/TP1/AN6
PA�
8
1�
PB6
9
1�
PB�/AN7
PB5
10
11
PB4/CLO
HT66F0174
20 DIP-A/SOP-A/SSOP-A
Rev. 1.00
8
July 11, 2013
HT66F0172/HT66F0174
Enhanced A/D Flash 8-Bit MCU
VSS&AVSS
1
�0
PC0/OSC1
�
19
PB0/INT0/AN0
PC1/OSC�
�
18
PB1/INT1/AN1
PC�
4
17
PB�/TCK0/AN�
PA0/TP0/ICPDA/OCDSDA
5
16
PA4/TCK1/AN�
PA1
6
15
PA5/AN4/VREF
PA�/ICPCK/OCDSCK
7
14
PA6/AN5
PA�
8
1�
PA7/TP1/AN6
PB6
9
1�
PB�/AN7
PB5
10
11
PB4/CLO
VDD&AVDD
HT66F0172
20 DIP-A/SOP-A/SSOP-A
Note: 1. If the pin-shared pin functions have multiple outputs simultaneously, its pin names at the
right side of the "/" sign can be used for higher priority
2. VDD&AVDD means the VDD and AVDD are the double bonding.
3. VSS&AVSS means the VSS and AVSS are the double bonding.
Pin Descriptions
With the exception of the power pins, all pins on these devices can be referenced by their Port name,
e.g. PA.0, PA.1etc, which refer to the digital I/O function of the pins. However these Port pins are
also shared with other function such as the Analog to Digital Converter, Timer Module pins etc.
The function of each pin is listed in the following table, however the details behind how each pin is
configured is contained in other sections of the datasheet.
Pin Name
PA0/TP0/
ICPDA/
OCDSDA
PA1
PA2/ICPCK
/OCDSCK
PA3
PA4/TCK1/
AN3
PA5/AN4/
VREF
Rev. 1.00
Function
OP
PA0
PAWU
PAPU
I/T
O/T
ST
General purpose I/O. Register enabled pull-up
CMOS
and wake-up.
Description
TP0
TMPC
—
CMOS TM0 output
ICPDA
—
ST
CMOS ICP Data/Address
OCDSDA
—
ST
CMOS OCDS Data/Address, for EV chip only
PA1
PAPU
PAWU
ST
CMOS
General purpose I/O. Register enabled pull-up
and wake-up.
PA2
PAPU
PAWU
ST
CMOS
General purpose I/O. Register enabled pull-up
and wake-up.
ICPCK
—
ST
—
ICP Clock pin
OCDSCK
—
ST
—
OCDS Clock pin, for EV chip only
PA3
PAPU
PAWU
ST
CMOS
General purpose I/O. Register enabled pull-up
and wake-up.
PA4
PAPU
PAWU
ST
CMOS
General purpose I/O. Register enabled pull-up
and wake-up.
TCK1
TM1C0
ST
—
TM1 clock input
AN3
ACERL
AN
—
A/D channel 3
PA5
PAPU
PAWU
ST
CMOS
AN4
ACERL
AN
—
A/D channel 4
VREF
ADCR1
AN
—
A/D Converter reference input
9
General purpose I/O. Register enabled pull-up
and wake-up.
July 11, 2013
HT66F0172/HT66F0174
Enhanced A/D Flash 8-Bit MCU
Pin Name
PA6/AN5
PA7/TP1/
AN6
PB0/INT0/
AN0/XT1
PB1/INT1/
AN1/XT2
PB2/TCK0/
AN2
PB3/AN7
PB4/CLO
PB5
PB6
PC0/OSC1
PC1/OSC2
Function
OP
PA6
PAPU
PAWU
I/T
O/T
Description
ST
AN5
ACERL
AN
—
PA7
PAPU
PAWU
ST
CMOS
CMOS TM1 output
General purpose I/O. Register enabled pull-up
CMOS
and wake-up.
A/D channel 5
General purpose I/O. Register enabled pull-up
and wake-up.
TP1
TMPC
—
AN6
ACERL
AN
PB0
PBPU
ST
INT0
INTC0
INTEG
ST
—
External Interrupt 0
AN0
ACERL
AN
—
A/D channel 0
XT1
CO
LXT
—
LXT oscillator pin
PB1
PBPU
ST
INT1
INTC2
INTEG
ST
—
External Interrupt 1
AN1
ARERL
ST
—
A/D channel 1
XT2
CO
—
PB2
PBPU
ST
—
A/D channel 6
CMOS General purpose I/O. Register enabled pull-up
CMOS General purpose I/O. Register enabled pull-up.
LXT
LXT oscillator pin
CMOS General purpose I/O. Register enabled pull-up.
TCK0
TM0C0
ST
—
TM0 clock input
AN2
ACERL
AN
—
A/D channel 2
PB3
PBPU
ST
AN7
ACERL
AN
CMOS General purpose I/O. Register enabled pull-up.
PB4
PBPU
ST
CMOS General purpose I/O. Register enabled pull-up.
CLO
TMPC
—
CMOS System Clock Output
PB5
PBPU
ST
CMOS General purpose I/O. Register enabled pull-up.
PB6
PBPU
ST
CMOS General purpose I/O. Register enabled pull-up.
PC0
PCPU
ST
CMOS General purpose I/O. Register enabled pull-up.
OSC1
CO
HXT
PC1
PCPU
ST
—
—
A/D channel 7
HXT oscillator pin
CMOS General purpose I/O. Register enabled pull-up.
OSC2
CO
—
PC2
PCPU
ST
VSS
VSS
—
PWR
—
Negative power supply, ground
AVSS
AVSS
—
PWR
—
Ground connection for A/D converter.
VDD
VDD
—
PWR
—
Positive power supply
AVDD
AVDD
—
PWR
—
Positive Power supply for A/D converter.
PC2
HXT
HXT oscillator pin
CMOS General purpose I/O. Register enabled pull-up.
Note: I/T: Input type; O/T: Output type.
OP: Optional by configuration option (CO) or register option.
PWR: Power;
ST: Schmitt Trigger input.
CMOS: CMOS output;
AN: Analog input pin.
HXT: High frequency crystal oscillator.
LXT: Low frequency crystal oscillator.
Rev. 1.00
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July 11, 2013
HT66F0172/HT66F0174
Enhanced A/D Flash 8-Bit MCU
Absolute Maximum Ratings
Supply Voltage.................................................................................................VSS−0.3V to VSS+6.0V
Input Voltage...................................................................................................VSS−0.3V to VDD+0.3V
Storage Temperature.....................................................................................................-50˚C to 150˚C
Operating Temperature...................................................................................................-40˚C to 85˚C
IOH Total...................................................................................................................................-100mA
IOL Total.................................................................................................................................... 100mA
Total Power Dissipation ......................................................................................................... 500mW
Note: These are stress ratings only. Stresses exceeding the range specified under "Absolute Maximum
Ratings" may cause substantial damage to these devices. Functional operation of these devices at
other conditions beyond those listed in the specification is not implied and prolonged exposure to
extreme conditions may affect devices reliability.
D.C. Characteristics
Ta= 25˚C
Symbol
VDD
Parameter
Operating Voltage
(HXT, HIRC)
Test Conditions
—
3V
5V
3V
IDD1
Operating Current
Normal Mode, fSYS=fH
(HXT)
5V
3V
5V
3V
5V
5V
IDD2
Operating Current
Normal Mode, fSYS=fH
(HIRC)
IDD3
Operating Current
Slow Mode, fSYS=fL=fLXT
fSUB=LXT
IDD4
Operating Current
Slow Mode, fSYS=fL=fLIRC
fSUB=LIRC
Rev. 1.00
Min.
Typ.
Max.
Unit
fSYS=8MHz
2.2
—
5.5
V
fSYS=12MHz
2.7
—
5.5
V
fSYS=20MHz
4.5
—
5.5
V
No load, fH=4MHz, ADC off,
WDT enable
—
0.7
1.1
mA
—
1.8
2.7
mA
No load, fH=8MHz, ADC off,
WDT enable
—
1.0
1.5
mA
—
2.5
4.0
mA
No load, fH=12MHz, ADC off,
WDT enable
—
1.5
2.5
mA
—
3.5
5.5
mA
No load, fH=16MHz, ADC off,
WDT enable
—
2.0
3.0
mA
—
4.5
7.0
mA
—
5.5
8.5
mA
—
2.0
2.8
mA
—
3.0
4.5
mA
No load, fSYS=LXT, ADC off,
WDT enable, LXTLP=0
—
10
20
μA
—
30
50
μA
No load, fSYS=LXT, ADC off,
WDT enable, LXTLP=1
—
10
20
μA
—
40
60
μA
—
10
20
μA
—
30
50
μA
VDD
3V
5V
3V
5V
3V
5V
3V
5V
Conditions
No load, fH=20MHz, ADC off,
WDT enable
No load, fH=8MHz, ADC off,
WDT enable
No load, fSYS=LIRC, ADC off,
WDT enable
11
July 11, 2013
HT66F0172/HT66F0174
Enhanced A/D Flash 8-Bit MCU
Symbol
Parameter
Test Conditions
3V
5V
3V
5V
IDD5
Operating Current
Normal Mode, fH=8MHz
(HIRC)
3V
5V
3V
5V
3V
5V
3V
5V
3V
IIDLE01
IDLE0 Mode Standby Current
(LXT on)
5V
3V
5V
IIDLE02
IDLE0 Mode Standby Current
(LIRC on)
3V
5V
3V
IIDLE03
IDLE0 Mode Standby Current
(LXT and LIRC on)
Min.
Typ.
Max.
Unit
No load, fSYS= fH/2, ADC off,
WDT enable
—
1.7
2.4
mA
—
2.6
4.4
mA
No load, fSYS= fH/4, ADC off,
WDT enable
—
1.6
2.4
mA
—
2.4
4.0
mA
No load, fSYS= fH/8, ADC off,
WDT enable
—
1.5
2.2
mA
—
2.2
3.6
mA
No load, fSYS= fH/16, ADC off,
WDT enable
—
1.4
2.0
mA
—
2.0
3.2
mA
No load, fSYS= fH/32, ADC off,
WDT enable
—
1.3
1.8
mA
—
1.8
2.8
mA
No load, fSYS= fH/64, ADC off,
WDT enable
—
1.2
1.6
mA
—
1.6
2.4
mA
No load, ADC off,
WDT enable, LXTLP=0
—
5
10
μA
—
16
32
μA
No load, ADC off,
WDT enable, LXTLP=1
—
5
10
μA
—
16
32
μA
No load, ADC off,
WDT enable, LVR disable
—
1.3
3.0
μA
—
2.2
5.0
μA
No load, ADC off,
WDT enable, LXTLP=0
—
6
12
μA
—
18
36
μA
No load, ADC off,
WDT enable, LXTLP=1
—
6
12
μA
—
18
36
μA
No load, ADC off,
WDT enable, fSYS= 4MHz on
—
0.4
0.8
mA
—
0.8
1.6
mA
No load, ADC off,
WDT enable, fSYS= 8MHz on
—
0.5
1.0
mA
—
1.0
2.0
mA
No load, ADC off,
WDT enable, fSYS= 8MHz on
—
0.8
1.6
mA
—
1.0
2.0
mA
No load, ADC off,
WDT enable, fSYS= 12MHz on
—
0.6
1.2
mA
—
1.2
2.4
mA
No load, ADC off,
WDT enable, fSYS= 16MHz on
—
1.0
2.0
mA
—
2.0
4.0
mA
—
2.5
5.0
mA
No load, ADC off,
WDT disable, LVR disable
—
0.1
1.0
μA
—
0.3
2.0
μA
No load, ADC off, WDT enable,
LXTLP=0, LVR disable
—
5
10
μA
—
16
32
μA
No load, ADC off, WDT enable,
LXTLP=1, LVR disable
—
5
10
μA
—
15
30
μA
—
1.3
5.0
μA
—
2.2
10
μA
VDD
5V
3V
5V
Conditions
IIDLE11
IDLE1 Mode Standby Current
(HXT on)
3V
IIDLE12
IDLE1 Mode Standby Current
(HXT on)
3V
IIDLE12A
IDLE1 Mode Standby Current
(HIRC on)
3V
IIDLE13
IDLE1 Mode Standby Current
(HXT on)
3V
IIDLE14
IDLE1 Mode Standby Current
(HXT on)
3V
IIDLE15
IDLE1 Mode Standby Current
(HXT on)
ISLEEP0
SLEEP0 Mode Standby Current
(LIRC off)
3V
ISLEEP11
SLEEP1 Mode Standby Current
(LXT on)
3V
ISLEEP12
SLEEP1 Mode Standby Current
(LXT on)
3V
ISLEEP13
SLEEP1 Mode Standby Current
(LIRC on)
3V
5V
No load, ADC off, WDT enable,
LVR disable
VIL
Input Low Voltage for I/O Ports,
or Input Pins
5V
—
0
—
1.5
V
—
—
0
—
0.2VDD
V
VIH
Input High Voltage for I/O Ports,
or Input Pins
5V
—
3.5
—
5.0
V
—
—
0.8VDD
—
VDD
V
Rev. 1.00
5V
5V
5V
5V
5V
5V
5V
5V
5V
No load, ADC off,
WDT enable, fSYS= 20MHz on
12
July 11, 2013
HT66F0172/HT66F0174
Enhanced A/D Flash 8-Bit MCU
Symbol
IOL
Parameter
I/O Port Sink Current
IOH
I/O Port Source Current
RPH
Pull-high Resistance for I/O
Ports
Test Conditions
VDD
Conditions
Min.
Typ.
Max.
Unit
3V
VOL=0.1VDD
4
8
—
mA
5V
VOL=0.1VDD
10
20
—
mA
3V
VOH=0.9VDD
-2
-4
—
mA
5V
VOH=0.9VDD
-5
-10
—
mA
3V
—
20
60
100
kΩ
5V
—
10
30
50
kΩ
A.C. Characteristics
Ta= 25˚C
Symbol
fCPU
fSYS
fHIRC
Parameter
Operating Clock
System Clock (HXT)
System Clock (HIRC)
Test Conditions
Min.
Typ.
Max.
Unit
—
DC
—
DC
—
8
MHz
—
12
4.5V~5.5V
—
MHz
DC
—
20
2.2V~5.5V
MHz
—
0.4
—
8
MHz
2.7V~5.5V
—
0.4
—
12
MHz
4.5V~5.5V
—
0.4
—
20
MHz
VDD
Conditions
2.2V~5.5V
2.7V~5.5V
3V/5V
Ta = 25°C
-2%
8
2%
MHz
3V/5V
Ta = 0°C ~ 70°C
-5%
8
5%
MHz
2.2V~5.5V
Ta = 0°C ~ 70°C
-7%
8
7%
MHz
2.2V~5.5V
Ta = -40°C ~ 85°C
-10%
8
10%
MHz
Ta = 25°C
-10%
32
+10%
kHz
Ta = -40°C ~ 85°C
-30%
32
+60%
kHz
5V
fLIRC
System Clock (LIRC)
tTIMER
TCKn Input Pulse Width
—
—
0.3
—
—
μs
tINT
Interrupt Pulse Width
—
—
10
—
—
μs
tEERD
EEPROM Read Time
—
—
—
2
4
tSYS
tEEWR
EEPROM Write Time
—
—
—
2
4
ms
System Start-up Timer Period
(Power On Reset)
—
—
—
128
—
System Start-up Timer Period
(Wake-up from HALT,
fSYS off at HALT State)
—
fSYS=HIRC
—
16
—
System Start-up Timer Period
(Wake-up from HALT,
fSYS off at HALT State)
—
fSYS=LIRC
—
2
—
System Start-up Timer Period
(Wake-up from HALT,
fSYS on at HALT State)
—
—
—
2
—
System Reset Delay Time
(Power On Reset, LVR Reset,
LVR S/W Reset (LVRC),
WDT S/W Reset (WDTC))
—
—
25
50
100
ms
System Reset Delay Time
(WDT Normal Reset)
—
—
8.3
16.7
33.3
ms
tSST
tRSTD
2.2V~5.5V
tSYS
Note: 1. tSYS=1/fSYS
2. To maintain the accuracy of the internal HIRC oscillator frequency, a 0.1μF decoupling capacitor should
be connected between VDD and VSS and located as close to the device as possible.
Rev. 1.00
13
July 11, 2013
HT66F0172/HT66F0174
Enhanced A/D Flash 8-Bit MCU
A/D Converter Characteristics
Ta= 25˚C
Symbol
Parameter
Test Conditions
VDD
Condition
Min.
Typ.
Max.
Unit
5.5
V
AVDD
A/D Converter Operating Voltage
—
—
2.7
—
VADI
A/D Converter Input Voltage
—
—
0
—
VREF
mA
VREF
A/D Converter Reference Voltage
—
—
2
—
AVDD
V
VBG
Reference Voltage with Buffer Voltage
—
—
-3%
1.25
+3%
V
VREF=AVDD=VDD
tADCK =0.5μs
Ta=25˚C
-3
—
+3
LSB
VREF=AVDD=VDD
tADCK =0.5μs
Ta=-40˚C ~ 85˚C
-4
—
+4
LSB
VREF=AVDD=VDD
tADCK =0.5μs
Ta=25˚C
-4
—
+4
LSB
VREF=AVDD=VDD
tADCK =0.5μs
Ta=-40˚C ~ 85˚C
-8
—
+8
LSB
2.7V
DNL1
Differential Non-linearity
3V
5V
2.7V
DNL2
Differential Non-linearity
3V
5V
2.7V
INL1
Integral Non-linearity
3V
5V
2.7V
INL2
Integral Non-linearity
3V
5V
3V
—
0.9
1.35
mA
—
1.2
1.8
mA
—
—
200
300
μA
—
0.5
—
10
μs
—
16
—
tADCK
—
4
—
tADCK
2
—
—
μs
200
—
—
μs
IADC
Additional Power Consumption if
A/D Converter is used
IBG
Additional Power Consumption if VBG
Reference with Buffer is used
—
tADCK
A/D Converter Clock Period
—
tADC
A/D Conversion Time
(Include Sample and Hold Time)
—
tADS
A/D Converter Sampling Time
—
—
tON2ST
A/D Converter On-to-Start Time
—
—
tBGS
VBG Turn on Stable Time
—
—
Rev. 1.00
5V
No load (tADCK =0.5μs )
12 bit ADC
14
July 11, 2013
HT66F0172/HT66F0174
Enhanced A/D Flash 8-Bit MCU
LVD&LVR Electrical Characteristics
Ta= 25˚C
Symbol
Parameter
Test Conditions
VDD
Min.
Conditions
Typ.
Max.
Unit
VLVR1
LVR Enable, 2.10V option
2.10
V
VLVR2
LVR Enable, 2.55V option
2.55
V
Low Voltage Reset Voltage
VLVR3
—
LVR Enable, 3.15V option
-5%
3.15
+5%
V
VLVR4
LVR Enable, 3.80V option
3.80
V
VLVD1
LVDEN=1, VLVD=2.0V
2.00
V
VLVD2
LVDEN=1, VLVD=2.2V
2.20
V
VLVD3
LVDEN=1, VLVD=2.4V
2.40
V
VLVD4
LVDEN=1, VLVD=2.7V
2.70
Low Voltage Detector Voltage
VLVD5
—
-5%
LVDEN=1, VLVD=3.0V
3.00
V
+5%
V
VLVD6
LVDEN=1, VLVD=3.3V
3.30
V
VLVD7
LVDEN=1, VLVD=3.6V
3.60
V
VLVD8
LVDEN=1, VLVD=4.0V
4.00
V
Additional Power Consumption if
LVR is Used
ILVR
3V
—
30
45
μA
—
60
90
μA
LVD disable → LVD enable
(LVR disable)
—
40
60
μA
—
75
115
μA
—
30
45
μA
5V
LVD disable → LVD enable
(LVR enable)
—
60
90
μA
LVR disable → LVR enable
5V
3V
Additional Power Consumption
if LVD is Used
ILVD
5V
3V
tLVR
Low Voltage Width to Reset
—
—
120
240
480
μS
tLVD
Low Voltage Width to Interrupt
—
—
20
45
90
μS
15
—
—
μS
45
90
120
μS
tLVDS
LVDO stable time
—
LVD off → LVD on
(LVR enable or disable)
tSRESET
Software Reset Width to Reset
—
—
Power on Reset Electrical Characteristics
Ta= 25˚C
Symbol
Test Conditions
Parameter
VDD Start Voltage to ensure Power-on
Reset
—
RRVDD
VDD Rise Rate to ensure Power-on Reset
—
Max.
Unit
—
—
—
100
mV
—
0.035
—
—
V/ms
—
Without 0.1μF between
VDD and VSS
2
—
—
μS
—
With 0.1μF between
VDD and VSS
10
—
—
μS
Power-on Reset Low Pulse Width
Typ.
Condition
VPOR
tPOR
Min.
VDD
Rev. 1.00
15
July 11, 2013
HT66F0172/HT66F0174
Enhanced A/D Flash 8-Bit MCU
System Architecture
A key factor in the high-performance features of the Holtek range of microcontrollers is attributed
to their internal system architecture. The device takes advantage of the usual features found within
RISC microcontrollers providing increased speed of operation and Periodic performance. The
pipelining scheme is implemented in such a way that instruction fetching and instruction execution
are overlapped, hence instructions are effectively executed in one cycle, with the exception of branch
or call instructions. An 8-bit wide ALU is used in practically all instruction set operations, which
carries out arithmetic operations, logic operations, rotation, increment, decrement, branch decisions,
etc. The internal data path is simplified by moving data through the Accumulator and the ALU.
Certain internal registers are implemented in the Data Memory and can be directly or indirectly
addressed. The simple addressing methods of these registers along with additional architectural
features ensure that a minimum of external components is required to provide a functional I/O and
A/D control system with maximum reliability and flexibility. This makes the device suitable for lowcost, high-volume production for controller applications.
Clocking and Pipelining
The main system clock, derived from HXT, LXT, HIRC or LIRC oscillator is subdivided into four
internally generated non-overlapping clocks, T1~T4. The Program Counter is incremented at the
beginning of the T1 clock during which time a new instruction is fetched. The remaining T2~T4
clocks carry out the decoding and execution functions. In this way, one T1~T4 clock cycle forms
one instruction cycle. Although the fetching and execution of instructions takes place in consecutive
instruction cycles, the pipelining structure of the microcontroller ensures that instructions are
effectively executed in one instruction cycle. The exception to this are instructions where the
contents of the Program Counter are changed, such as subroutine calls or jumps, in which case the
instruction will take one more instruction cycle to execute.
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
   
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System Clock and Pipelining
Rev. 1.00
16
July 11, 2013
HT66F0172/HT66F0174
Enhanced A/D Flash 8-Bit MCU
For instructions involving branches, such as jump or call instructions, two machine cycles are
required to complete instruction execution. An extra cycle is required as the program takes one
cycle to first obtain the actual jump or call address and then another cycle to actually execute the
branch. The requirement for this extra cycle should be taken into account by programmers in timing
sensitive applications.
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Instruction Fetching
Program Counter
During program execution, the Program Counter is used to keep track of the address of the
next instruction to be executed. It is automatically incremented by one each time an instruction
is executed except for instructions, such as "JMP" or "CALL" that demand a jump to a nonconsecutive Program Memory address. Only the lower 8 bits, known as the Program Counter Low
Register, are directly addressable by the application program.
When executing instructions requiring jumps to non-consecutive addresses such as a jump
instruction, a subroutine call, interrupt or reset, etc., the microcontroller manages program control
by loading the required address into the Program Counter. For conditional skip instructions, once
the condition has been met, the next instruction, which has already been fetched during the present
instruction execution, is discarded and a dummy cycle takes its place while the correct instruction is
obtained.
Program Counter
Program Counter High Byte
PCL Register
PC10~PC8
PCL7~PCL0
The lower byte of the Program Counter, known as the Program Counter Low register or PCL, is
available for program control and is a readable and writeable register. By transferring data directly
into this register, a short program jump can be executed directly, however, as only this low byte
is available for manipulation, the jumps are limited to the present page of memory, that is 256
locations. When such program jumps are executed it should also be noted that a dummy cycle
will be inserted. Manipulating the PCL register may cause program branching, so an extra cycle is
needed to pre-fetch.
Rev. 1.00
17
July 11, 2013
HT66F0172/HT66F0174
Enhanced A/D Flash 8-Bit MCU
Stack
This is a special part of the memory which is used to save the contents of the Program Counter
only. The stack is neither part of the data nor part of the program space, and is neither readable nor
writeable. The activated level is indexed by the Stack Pointer, and is neither readable nor writeable.
At a subroutine call or interrupt acknowledge signal, the contents of the Program Counter are pushed
onto the stack. At the end of a subroutine or an interrupt routine, signaled by a return instruction,
RET or RETI, the Program Counter is restored to its previous value from the stack. After a device
reset, the Stack Pointer will point to the top of the stack.
If the stack is full and an enabled interrupt takes place, the interrupt request flag will be recorded
but the acknowledge signal will be inhibited. When the Stack Pointer is decremented, by RET or
RETI, the interrupt will be serviced. This feature prevents stack overflow allowing the programmer
to use the structure more easily. However, when the stack is full, a CALL subroutine instruction can
still be executed which will result in a stack overflow. Precautions should be taken to avoid such
cases which might cause unpredictable program branching. If the stack is overflow, the first Program
Counter save in the stack will be lost.
P ro g ra m
T o p o f S ta c k
C o u n te r
S ta c k L e v e l 1
S ta c k L e v e l 2
S ta c k
P o in te r
B o tto m
S ta c k L e v e l 3
o f S ta c k
P ro g ra m
M e m o ry
S ta c k L e v e l 8
Arithmetic and Logic Unit – ALU
The arithmetic-logic unit or ALU is a critical area of the microcontroller that carries out arithmetic
and logic operations of the instruction set. Connected to the main microcontroller data bus, the ALU
receives related instruction codes and performs the required arithmetic or logical operations after
which the result will be placed in the specified register. As these ALU calculation or operations may
result in carry, borrow or other status changes, the status register will be correspondingly updated to
reflect these changes. The ALU supports the following functions:
• Arithmetic operations: ADD, ADDM, ADC, ADCM, SUB, SUBM, SBC, SBCM, DAA
• Logic operations: AND, OR, XOR, ANDM, ORM, XORM, CPL, CPLA
• Rotation RRA, RR, RRCA, RRC, RLA, RL, RLCA, RLC
• Increment and Decrement INCA, INC, DECA, DEC
• Branch decision, JMP, SZ, SZA, SNZ, SIZ, SDZ, SIZA, SDZA, CALL, RET, RETI
Rev. 1.00
18
July 11, 2013
HT66F0172/HT66F0174
Enhanced A/D Flash 8-Bit MCU
Flash Program Memory
The Program Memory is the location where the user code or program is stored. For this device the
Program Memory is Flash type, which means it can be programmed and re-programmed a large
number of times, allowing the user the convenience of code modification on the same device.
By using the appropriate programming tools, this Flash device offers users the flexibility to
conveniently debug and develop their applications while also offering a means of field programming
and updating.
Structure
The Program Memory has a capacity of 2K×16 bits. The Program Memory is addressed by the
Program Counter and also contains data, table information and interrupts entries. Table data, which
can be setup in any location within the Program Memory, is addressed by a separate table pointer
register.
000 H
004 H
0�4 H
7FFH
Reset
Interr�pt
Vector
16 bits
Program Memory Structure
Special Vectors
Within the Program Memory, certain locations are reserved for the reset and interrupts. The location
000H is reserved for use by the device reset for program initialisation. After a device reset is
initiated, the program will jump to this location and begin execution.
Look-up Table
Any location within the Program Memory can be defined as a look-up table where programmers can
store fixed data. To use the look-up table, the table pointer must first be setup by placing the address
of the look up data to be retrieved in the table pointer register, TBLP and TBHP. These registers
define the total address of the look-up table.
After setting up the table pointer, the table data can be retrieved from the Program Memory using
the "TABRD[m]" or "TABRDL[m]" instructions, respectively. When the instruction is executed,
the lower order table byte from the Program Memory will be transferred to the user defined
Data Memory register [m] as specified in the instruction. The higher order table data byte from
the Program Memory will be transferred to the TBLH special register. Any unused bits in this
transferred higher order byte will be read as "0".
The accompanying diagram illustrates the addressing data flow of the look-up table.
A d d re s s
L a s t p a g e o r
T B H P R e g is te r
T B L P R e g is te r
Rev. 1.00
D a ta
1 6 b its
R e g is te r T B L H
U s e r S e le c te d
R e g is te r
H ig h B y te
L o w B y te
19
July 11, 2013
HT66F0172/HT66F0174
Enhanced A/D Flash 8-Bit MCU
Instruction
Table Location Bits
b10
b9
b8
b7
b6
b5
b4
b3
b2
b1
b0
TABRD [m]
@10
@9
@8
@7
@6
@5
@4
@3
@2
@1
@0
TABRDL [m]
1
1
1
@7
@6
@5
@4
@3
@2
@1
@0
Table Location
Note: b10~b0: Table location bits
@[email protected]: Table pointer (TBLP) bits
@[email protected]: Table pointer (TBHP) bits
Table Program Example
The following example shows how the table pointer and table data is defined and retrieved from the
microcontroller. This example uses raw table data located in the Program Memory which is stored
there using the ORG statement. The value at this ORG statement is "700H" which refers to the start
address of the last page within the 2K words Program Memory of the device. The table pointer is setup
here to have an initial value of "06H". This will ensure that the first data read from the data table will
be at the Program Memory address "706H" or 6 locations after the start of the last page. Note that the
value for the table pointer is referenced to the first address of the present page if the "TABRD [m]"
instruction is being used. The high byte of the table data which in this case is equal to zero will be
transferred to the TBLH register automatically when the "TABRD [m]" instruction is executed.
Because the TBLH register is a read-only register and cannot be restored, care should be taken
to ensure its protection if both the main routine and Interrupt Service Routine use table read
instructions. If using the table read instructions, the Interrupt Service Routines may change the
value of the TBLH and subsequently cause errors if used again by the main routine. As a rule it is
recommended that simultaneous use of the table read instructions should be avoided. However, in
situations where simultaneous use cannot be avoided, the interrupts should be disabled prior to the
execution of any main routine table-read instructions. Note that all table related instructions require
two instruction cycles to complete their operation.
Table Read Program Example
tempreg1 db ? ; temporary register #1
tempreg2 db ? ; temporary register #2
:
:
mov a,06h ; initialise low table pointer - note that this address is referenced
mov tblp,a
mov a,07h ; initialise high table pointer
mov tbhp,a
:
:
tabrd tempreg1 ; transfers value in table referenced by table pointer data at program
; memory address "706H" transferred to tempreg1 and TBLH
dec tblp ; reduce value of table pointer by one
tabrd tempreg2 ; transfers value in table referenced by table pointer data at program
; memory address "705H" transferred to tempreg2 and TBLH in this
; example the data "1AH" is transferred to tempreg1 and data "0FH" to
; register tempreg2
:
:
org 700h; sets initial address of program memory
dc 00Ah, 00Bh, 00Ch, 00Dh, 00Eh, 00Fh, 01Ah, 01Bh
:
:
Rev. 1.00
20
July 11, 2013
HT66F0172/HT66F0174
Enhanced A/D Flash 8-Bit MCU
In Circuit Programming
The provision of Flash type Program Memory provides the user with a means of convenient and easy
upgrades and modifications to their programs on the same device. As an additional convenience,
Holtek has provided a means of programming the microcontroller in-circuit using a 4-pin interface.
This provides manufacturers with the possibility of manufacturing their circuit boards complete with
a programmed or un-programmed microcontroller, and then programming or upgrading the program
at a later stage. This enables product manufacturers to easily keep their manufactured products
supplied with the latest program releases without removal and re-insertion of the device.
The Holtek Flash MCU to Writer Programming Pin correspondence table is as follows:
Holtek Write Pins
MCU Programming Pins
ICPDA
PA0
Function
Programming Serial Data/Address
ICPCK
PA2
Programming Serial Clock
VDD
VDD
Power Supply
VSS
VSS
Ground
During the programming process, the user must there take care to ensure that no other outputs
are connected to these two pins. The Program Memory and EEPROM data memory can both be
programmed serially in-circuit using this 4-wire interface. Data is downloaded and uploaded serially
on a single pin with an additional line for the clock. Two additional lines are required for the power
supply. The technical details regarding the in-circuit programming of the device are beyond the
scope of this document and will be supplied in supplementary literature.
M C U
P r o g r a m m in g P in s
W r ite r
C o n n e c to r S ig n a ls
W r ite r _ V D D
V D D
IC P D A
P A 0
IC P C K
P A 2
W r ite r _ V S S
V S S
*
*
T o o th e r C ir c u it
Note: * may be resistor or capacitor. The resistance of * must be greater than 1k or the capacitance
of * must be less than 1nF.
Rev. 1.00
21
July 11, 2013
HT66F0172/HT66F0174
Enhanced A/D Flash 8-Bit MCU
On-Chip Debug Support – OCDS
An EV chip exists for the purposes of device emulation. This EV chip device also provides an
"On-Chip Debug" function to debug the device during the development process. The EV chip
and the actual MCU device are almost functionally compatible except for the "On-Chip Debug"
function. Users can use the EV chip device to emulate the real chip device behavior by connecting
the OCDSDA and OCDSCK pins to the Holtek HT-IDE development tools. The OCDSDA pin is
the OCDS Data/Address input/output pin while the OCDSCK pin is the OCDS clock input pin.
When users use the EV chip for debugging, other functions which are shared with the OCDSDA
and OCDSCK pins in the actual MCU device will have no effect in the EV chip. However, the two
OCDS pins which are pin-shared with the ICP programming pins are still used as the Flash Memory
programming pins for ICP. For a more detailed OCDS description, refer to the corresponding
document named "Holtek e-Link for 8-bit MCU OCDS User’s Guide".
Holtek e-Link Pins
EV Chip Pins
Pin Description
OCDSDA
OCDSDA
On-chip Debug Support Data/Address input/output
OCDSCK
OCDSCK
On-chip Debug Support Clock input
VDD
VDD
Power Supply
GND
VSS
Ground
RAM Data Memory
The Data Memory is a volatile area of 8-bit wide RAM internal memory and is the location where
temporary information is stored. The RAM Data Memory capacity is 128 × 8 bits.
Structure
Divided into two sections, the first of these is an area of RAM, known as the Special Function Data
Memory. Here are located registers which are necessary for correct operation of the device. Many
of these registers can be read from and written to directly under program control, however, some
remain protected from user manipulation. The second area of Data Memory is known as the General
Purpose Data Memory, which is reserved for general purpose use. All locations within this area are
read and write accessible under program control.
Rev. 1.00
Capacity
Banks
128 × 8
0: 80H~FFH
22
July 11, 2013
HT66F0172/HT66F0174
Enhanced A/D Flash 8-Bit MCU
HT66F0174
00H
01H
0�H
0�H
04H
05H
06H
07H
08H
09H
0AH
0BH
0CH
0DH
0EH
0FH
10H
11H
1�H
1�H
14H
15H
16H
17H
18H
19H
1AH
1BH
1CH
1DH
1EH
1FH
�0H
�1H
��H
��H
�4H
Bank 0 Bank 1
IAR0
MP0
IAR1
MP1
BP
ACC
PCL
TBLP
TBLH
TBHP
STATUS
SMOD
LVDC
INTEG
INTC0
INTC1
INTC�
MFI0
MFI1
MFI�
PA
PAC
PCPU
PAWU
Un�sed
TMPC
WDTC
TBC
Un�sed
Un�sed
EEA
EED
ADRL
ADRH
ADCR0
ADCR1
ACERL
�5H
�6H
�7H
�8H
�9H
�AH
�BH
�CH
�DH
�EH
�FH
�0H
�1H
��H
��H
�4H
�5H
�6H
�7H
�8H
�9H
�AH
�BH
�CH
�DH
�EH
HT66F0172
Bank 0 Bank 1
Un�sed
CTRL
LVRC
TM0C0
TM0C1
TM0DL
TM0DH
TM0AL
TM0AH
TM0RPL
TM0RPH
TM1C0
TM1C1
TM1DL
TM1DH
TM1AL
TM1AH
TM1RPL
TM1RPH
00H
01H
0�H
0�H
04H
05H
06H
07H
08H
09H
0AH
0BH
0CH
0DH
0EH
0FH
10H
11H
1�H
1�H
14H
15H
16H
17H
18H
19H
1AH
1BH
1CH
1DH
1EH
1FH
�0H
�1H
��H
��H
�4H
Un�sed
PC
PCC
PCPU
PB
PBC
PBPU
�FH
40H Read 0 on�� EEC
Un�sed
7FH
: Un�sed� read as 00H
Bank 0 Bank 1
IAR0
MP0
IAR1
MP1
BP
ACC
PCL
TBLP
TBLH
TBHP
STATUS
SMOD
LVDC
INTEG
INTC0
INTC1
INTC�
MFI0
MFI1
MFI�
PA
PAC
PCPU
PAWU
Un�sed
TMPC
WDTC
TBC
Un�sed
Un�sed
Un�sed
Un�sed
ADRL
ADRH
ADCR0
ADCR1
ACERL
�5H
�6H
�7H
�8H
�9H
�AH
�BH
�CH
�DH
�EH
�FH
�0H
�1H
��H
��H
�4H
�5H
�6H
�7H
�8H
�9H
�AH
�BH
�CH
�DH
�EH
�FH
40H
Bank 0 Bank 1
Un�sed
CTRL
LVRC
TM0C0
TM0C1
TM0DL
TM0DH
TM0AL
TM0AH
TM0RPL
TM0RPH
TM1C0
TM1C1
TM1DL
TM1DH
TM1AL
TM1AH
TM1RPL
TM1RPH
Un�sed
PC
PCC
PCPU
PB
PBC
PBPU
Read 0 on��
Un�sed
7FH
: Un�sed� read as 00H
Data Memory Structure
The overall Data Memory is subdivided into two banks. The Special Purpose Data Memory registers are
accessible in all banks, with the exception of the EEC register at address 40H, which is only accessible
in Bank 1. Switching between the different Data Memory banks is achieved by setting the Bank Pointer
to the correct value. The start address of the Data Memory for the device is the address 00H.
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Special Function Register Description
Most of the Special Function Register details will be described in the relevant functional sections,
however several registers require a separate description in this section.
Indirect Addressing Registers – IAR0, IAR1
The Indirect Addressing Registers, IAR0 and IAR1, although having their locations in normal RAM
register space, do not actually physically exist as normal registers. The method of indirect addressing
for RAM data manipulation uses these Indirect Addressing Registers and Memory Pointers, in
contrast to direct memory addressing, where the actual memory address is specified. Actions on the
IAR0 and IAR1 registers will result in no actual read or write operation to these registers but rather
to the memory location specified by their corresponding Memory Pointers, MP0 or MP1. Acting as a
pair, IAR0 and MP0 can together access data from Bank 0 while the IAR1 and MP1 register pair can
access data from any bank. As the Indirect Addressing Registers are not physically implemented,
reading the Indirect Addressing Registers indirectly will return a result of "00H" and writing to the
registers indirectly will result in no operation.
Memory Pointers – MP0, MP1
Two Memory Pointers, known as MP0 and MP1 are provided. These Memory Pointers are
physically implemented in the Data Memory and can be manipulated in the same way as normal
registers providing a convenient way with which to address and track data. When any operation to
the relevant Indirect Addressing Registers is carried out, the actual address that the microcontroller
is directed to is the address specified by the related Memory Pointer. MP0, together with Indirect
Addressing Register, IAR0, are used to access data from Bank 0, while MP1 and IAR1 are used to
access data from all banks according to BP register. Direct Addressing can only be used with Bank 0,
all other Banks must be addressed indirectly using MP1 and IAR1.
The following example shows how to clear a section of four Data Memory locations already defined
as locations adres1 to adres4.
Indirect Addressing Program Example
data .section ´data´
adres1 db ?
adres2 db ?
adres3 db ?
adres4 db ?
block db ?
code .section at 0 ´code´
org 00h
start:
mov a,04h ; setup size of block
mov block,a
mov a,offset adres1 ; Accumulator loaded with first RAM address
mov mp0,a ; setup memory pointer with first RAM address
loop:
clr IAR0 ; clear the data at address defined by mp0
inc mp0; increment memory pointer
sdz block ; check if last memory location has been cleared
jmp loop
continue:
The important point to note here is that in the example shown above, no reference is made to specific
Data Memory addresses.
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Bank Pointer – BP
For this device, the Data Memory is divided into two banks, Bank0 and Bank1. Selecting the
required Data Memory area is achieved using the Bank Pointer. Bit 0 of the Bank Pointer is used to
select Data Memory Banks 0~1.
The Data Memory is initialised to Bank 0 after a reset, except for a WDT time-out reset in the Power
Down Mode, in which case, the Data Memory bank remains unaffected. It should be noted that the
Special Function Data Memory is not affected by the bank selection, which means that the Special
Function Registers can be accessed from within any bank. Directly addressing the Data Memory
will always result in Bank 0 being accessed irrespective of the value of the Bank Pointer. Accessing
data from Bank1 must be implemented using Indirect Addressing.
BP Register
Bit
7
6
5
4
3
2
1
0
Name
—
—
—
—
—
—
—
DMBP0
R/W
—
—
—
—
—
—
—
R/W
POR
—
—
—
—
—
—
—
0
Bit 7 ~ 1
Unimplemented, read as "0"
Bit 0DMBP0: Select Data Memory Banks
0: Bank 0
1: Bank 1
Accumulator – ACC
The Accumulator is central to the operation of any microcontroller and is closely related with
operations carried out by the ALU. The Accumulator is the place where all intermediate results
from the ALU are stored. Without the Accumulator it would be necessary to write the result of
each calculation or logical operation such as addition, subtraction, shift, etc., to the Data Memory
resulting in higher programming and timing overheads. Data transfer operations usually involve
the temporary storage function of the Accumulator; for example, when transferring data between
one user-defined register and another, it is necessary to do this by passing the data through the
Accumulator as no direct transfer between two registers is permitted.
Program Counter Low Register – PCL
To provide additional program control functions, the low byte of the Program Counter is made
accessible to programmers by locating it within the Special Purpose area of the Data Memory. By
manipulating this register, direct jumps to other program locations are easily implemented. Loading
a value directly into this PCL register will cause a jump to the specified Program Memory location,
however, as the register is only 8-bit wide, only jumps within the current Program Memory page are
permitted. When such operations are used, note that a dummy cycle will be inserted.
Look-up Table Registers – TBLP, TBHP, TBLH
These three special function registers are used to control operation of the look-up table which is
stored in the Program Memory. TBLP and TBHP are the table pointers and indicate the location
where the table data is located. Their value must be setup before any table read commands are
executed. Their value can be changed, for example using the "INC" or "DEC" instructions, allowing
for easy table data pointing and reading. TBLH is the location where the high order byte of the table
data is stored after a table read data instruction has been executed. Note that the lower order table
data byte is transferred to a user defined location.
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Status Register – STATUS
This 8-bit register contains the zero flag (Z), carry flag (C), auxiliary carry flag (AC), overflow flag
(OV), power down flag (PDF), and watchdog time-out flag (TO). These arithmetic/logical operation
and system management flags are used to record the status and operation of the microcontroller.
With the exception of the TO and PDF flags, bits in the status register can be altered by instructions
like most other registers. Any data written into the status register will not change the TO or PDF flag.
In addition, operations related to the status register may give different results due to the different
instruction operations. The TO flag can be affected only by a system power-up, a WDT time-out or
by executing the "CLR WDT" or "HALT" instruction. The PDF flag is affected only by executing
the "HALT" or "CLR WDT" instruction or during a system power-up.
The Z, OV, AC and C flags generally reflect the status of the latest operations.
• C is set if an operation results in a carry during an addition operation or if a borrow does not take
place during a subtraction operation; otherwise C is cleared. C is also affected by a rotate through
carry instruction.
• AC is set if an operation results in a carry out of the low nibbles in addition, or no borrow from
the high nibble into the low nibble in subtraction; otherwise AC is cleared.
• Z is set if the result of an arithmetic or logical operation is zero; otherwise Z is cleared.
• OV is set if an operation results in a carry into the highest-order bit but not a carry out of the
highest-order bit, or vice versa; otherwise OV is cleared.
• PDF is cleared by a system power-up or executing the "CLR WDT" instruction. PDF is set by
executing the "HALT" instruction.
• TO is cleared by a system power-up or executing the "CLR WDT" or "HALT" instruction. TO is
set by a WDT time-out.
In addition, on entering an interrupt sequence or executing a subroutine call, the status register will
not be pushed onto the stack automatically. If the contents of the status registers are important and if
the subroutine can corrupt the status register, precautions must be taken to correctly save it.
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STATUS Register
Bit
7
6
5
4
3
2
1
0
Name
—
—
TO
PDF
OV
Z
AC
C
R/W
—
—
R
R
R/W
R/W
R/W
R/W
POR
—
—
0
0
x
x
x
x
"×" unknown
Bit 7 ~ 6
Unimplemented, read as "0"
Bit 5TO: Watchdog Time-Out flag
0: After power up or executing the "CLR WDT" or "HALT" instruction
1: A watchdog time-out occurred.
Bit 4PDF: Power down flag
0: After power up or executing the "CLR WDT" instruction
1: By executing the "HALT" instruction
Bit 3OV: Overflow flag
0: no overflow
1: an operation results in a carry into the highest-order bit but not a carry out of the
highest-order bit or vice versa.
Bit 2Z: Zero flag
0: The result of an arithmetic or logical operation is not zero
1: The result of an arithmetic or logical operation is zero
Bit 1AC: Auxiliary flag
0: no auxiliary carry
1: an operation results in a carry out of the low nibbles in addition, or no borrow
from the high nibble into the low nibble in subtraction
Bit 0C: Carry flag
0: no carry-out
1: an operation results in a carry during an addition operation or if a borrow does not
take place during a subtraction operation
C is also affected by a rotate through carry instruction.
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EEPROM Data Memory (only for HT66F0174)
One of the special features in the device is its internal EEPROM Data Memory. EEPROM, which
stands for Electrically Erasable Programmable Read Only Memory, is by its nature a non-volatile
form of memory, with data retention even when its power supply is removed. By incorporating
this kind of data memory, a whole new host of application possibilities are made available to the
designer. The availability of EEPROM storage allows information such as product identification
numbers, calibration values, specific user data, system setup data or other product information to
be stored directly within the product microcontroller. The process of reading and writing data to the
EEPROM memory has been reduced to a very trivial affair.
EEPROM Data Memory Structure
The EEPROM Data Memory capacity is 64×8 bits. Unlike the Program Memory and RAM Data
Memory, the EEPROM Data Memory is not directly mapped into memory space and is therefore
not directly accessible in the same way as the other types of memory. Instead it has to be accessed
indirectly through the EEPROM control registers.
EEPROM Registers
Three registers control the overall operation of the internal EEPROM Data Memory. These are the
address register, EEA, the data register, EED and a single control register, EEC. As both the EEA
and EED registers are located in Bank 0, they can be directly accessed in the same way as any other
Special Function Register. The EEC register however, being located in Bank1, cannot be directly
addressed directly and can only be read from or written to indirectly using the MP1 Memory Pointer
and Indirect Addressing Register, IAR1. Because the EEC control register is located at address 40H
in Bank 1, the MP1 Memory Pointer must first be set to the value 40H and the Bank Pointer register,
BP, set to the value, 01H, before any operations on the EEC register are executed.
EEPROM Control Registers List
Name
Bit
7
6
5
4
3
2
1
0
EEA
—
—
D5
D4
D3
D2
D1
D0
EED
D7
D6
D5
D4
D3
D2
D1
D0
EEC
—
—
—
—
WREN
WR
RDEN
RD
EEA Register
Bit
7
6
5
4
3
2
1
0
Name
—
—
D5
D4
D3
D2
D1
D0
R/W
—
—
R/W
R/W
R/W
R/W
R/W
R/W
POR
—
—
0
0
0
0
0
0
Bit 7 ~ 6
Unimplemented, read as "0"
Bit 5 ~ 0D5~D0: Data EEPROM address
Data EEPROM address bit 5 ~ bit 0
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EED Register
Bit
7
6
5
4
3
2
1
0
Name
D7
D6
D5
D4
D3
D2
D1
D0
R/W
R/W
R/W
R/W
R/W
R/W
R/W
R/W
R/W
POR
0
0
0
0
0
0
0
0
2
1
0
Bit 7 ~ 0
D7~D0: Data EEPROM data
Data EEPROM data bit 7 ~ bit 0
EEC Register
Bit
7
6
5
4
3
Name
—
—
—
—
WREN
WR
RDEN
RD
R/W
—
—
—
—
R/W
R/W
R/W
R/W
POR
—
—
—
—
0
0
0
0
Bit 7 ~ 4
Unimplemented, read as "0"
Bit 3WREN: Data EEPROM Write Enable
0: Disable
1: Enable
This is the Data EEPROM Write Enable Bit which must be set high before Data
EEPROM write operations are carried out. Clearing this bit to zero will inhibit Data
EEPROM write operations.
Bit 2WR: EEPROM Write Control
0: Write cycle has finished
1: Activate a write cycle
This is the Data EEPROM Write Control Bit and when set high by the application
program will activate a write cycle. This bit will be automatically reset to zero by the
hardware after the write cycle has finished. Setting this bit high will have no effect if
the WREN has not first been set high.
Bit 1RDEN: Data EEPROM Read Enable
0: Disable
1: Enable
This is the Data EEPROM Read Enable Bit which must be set high before Data
EEPROM read operations are carried out. Clearing this bit to zero will inhibit Data
EEPROM read operations.
Bit 0RD: EEPROM Read Control
0: Read cycle has finished
1: Activate a read cycle
This is the Data EEPROM Read Control Bit and when set high by the application
program will activate a read cycle. This bit will be automatically reset to zero by the
hardware after the read cycle has finished. Setting this bit high will have no effect if
the RDEN has not first been set high.
Note: The WREN, WR, RDEN and RD can not be set to "1" at the same time in one instruction.
The WR and RD can not be set to "1" at the same time.
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Reading Data from the EEPROM
To read data from the EEPROM, the read enable bit, RDEN, in the EEC register must first be set
high to enable the read function. The EEPROM address of the data to be read must then be placed
in the EEA register. If the RD bit in the EEC register is now set high, a read cycle will be initiated.
Setting the RD bit high will not initiate a read operation if the RDEN bit has not been set. When
the read cycle terminates, the RD bit will be automatically cleared to zero, after which the data can
be read from the EED register. The data will remain in the EED register until another read or write
operation is executed. The application program can poll the RD bit to determine when the data is
valid for reading.
Writing Data to the EEPROM
The EEPROM address of the data to be written must first be placed in the EEA register and the data
placed in the EED register. To write data to the EEPROM, the write enable bit, WREN, in the EEC
register must first be set high to enable the write function. After this, the WR bit in the EEC register
must be immediately set high to initiate a write cycle. These two instructions must be executed
consecutively. The global interrupt bit EMI should also first be cleared before implementing any
write operations, and then set again after the write cycle has started. Note that setting the WR bit
high will not initiate a write cycle if the WREN bit has not been set. As the EEPROM write cycle is
controlled using an internal timer whose operation is asynchronous to microcontroller system clock,
a certain time will elapse before the data will have been written into the EEPROM. Detecting when
the write cycle has finished can be implemented either by polling the WR bit in the EEC register or
by using the EEPROM interrupt. When the write cycle terminates, the WR bit will be automatically
cleared to zero by the microcontroller, informing the user that the data has been written to the
EEPROM. The application program can therefore poll the WR bit to determine when the write cycle
has ended.
Write Protection
Protection against inadvertent write operation is provided in several ways. After the device is
powered-on the Write Enable bit in the control register will be cleared preventing any write
operations. Also at power-on the Bank Pointer, BP, will be reset to zero, which means that Data
Memory Bank 0 will be selected. As the EEPROM control register is located in Bank 1, this adds a
further measure of protection against spurious write operations. During normal program operation,
ensuring that the Write Enable bit in the control register is cleared will safeguard against incorrect
write operations.
EEPROM Interrupt
The EEPROM write interrupt is generated when an EEPROM write cycle has ended. The EEPROM
interrupt must first be enabled by setting the DEE bit in the relevant interrupt register. However as
the EEPROM is contained within a Multi-function Interrupt, the associated multi-function interrupt
enable bit must also be set. When an EEPROM write cycle ends, the DEF request flag and its
associated multi-function interrupt request flag will both be set. If the global, EEPROM and Multifunction interrupts are enabled and the stack is not full, a jump to the associated Multi-function
Interrupt vector will take place. When the interrupt is serviced only the Multi-function interrupt flag
will be automatically reset, the EEPROM interrupt flag must be manually reset by the application
program.
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Programming Considerations
Care must be taken that data is not inadvertently written to the EEPROM. Protection can be Periodic
by ensuring that the Write Enable bit is normally cleared to zero when not writing. Also the Bank
Pointer could be normally cleared to zero as this would inhibit access to Bank 1 where the EEPROM
control register exist. Although certainly not necessary, consideration might be given in the
application program to the checking of the validity of new write data by a simple read back process.
When writing data the WR bit must be set high immediately after the WREN bit has been set high,
to ensure the write cycle executes correctly. The global interrupt bit EMI should also be cleared
before a write cycle is executed and then re-enabled after the write cycle starts.
Programming Examples
• Reading data from the EEPROM - polling method
MOV A, EEPROM_ADRES MOV EEA, A
MOV A, 040H
MOV MP1, A
MOV A, 01H
MOV BP, A
SET IAR1.1
SET IAR1.0
BACK:
SZ IAR1.0
JMP BACK
CLR IAR1
CLR BP
MOV A, EED
MOV READ_DATA, A
; user defined address
; setup memory pointer MP1
; MP1 points to EEC register
; setup Bank Pointer
; set RDEN bit, enable read operations
; start Read Cycle - set RD bit
; check for read cycle end
; disable EEPROM write
; move read data to register
• Writing Data to the EEPROM - polling method
MOV A, EEPROM_ADRES
MOV EEA, A
MOV A, EEPROM_DATA
MOV EED, A
MOV A, 040H
MOV MP1, A
MOV A, 01H
MOV BP, A
CLR EMI
SET IAR1.3
SET IAR1.2
SET EMI
BACK:
SZ IAR1.2
JMP BACK
CLR IAR1
CLR BP
Rev. 1.00
; user defined address
; user defined data
; setup memory pointer MP1
; MP1 points to EEC register
; setup Bank Pointer
; set WREN bit, enable write operations
; start Write Cycle - set WR bit
; check for write cycle end
; disable EEPROM write
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Enhanced A/D Flash 8-Bit MCU
Oscillator
Various oscillator options offer the user a wide range of functions according to their various
application requirements. The flexible features of the oscillator functions ensure that the best
optimisation can be achieved in terms of speed and power saving. Oscillator selections and operation
are selected through registers.
Oscillator Overview
In addition to being the source of the main system clock the oscillators also provide clock sources
for the Watchdog Timer and Time Base Interrupts. External oscillators requiring some external
components as well as fully integrated internal oscillators, requiring no external components,
are provided to form a wide range of both fast and slow system oscillators. All oscillator options
are selected through the configuration options. The higher frequency oscillators provide higher
performance but carry with it the disadvantage of higher power requirements, while the opposite
is of course true for the lower frequency oscillators. With the capability of dynamically switching
between fast and slow system clock, the device has the flexibility to optimize the performance/
power ratio, a feature especially important in power sensitive portable applications.
Name
Freq.
Pins
External Crystal
Type
HXT
400kHz~20MHz
OSC1/OSC2
Internal High Speed RC
HIRC
8MHz
—
External Low Speed Crystal
LXT
32.768kHz
XT1/XT2
Internal Low Speed RC
LIRC
32kHz
—
Oscillator Types
System Clock Configurations
There are four methods of generating the system clock, high speed oscillators and low speed
oscillators. The high speed oscillators are the external crystal/ ceramic oscillator and the internal
8MHz RC oscillator. The low speed oscillator is the internal 32kHz (LIRC) oscillator and the
external 32.768kHz crystal oscillator. Note that there isn't the external 32.768kHz crystal oscillator
in HT66F0172. So the low speed oscillator for the HT66F0172 is only the internal 32kHz (LIRC)
oscillator. Selecting whether the low or high speed oscillator is used as the system oscillator is
implemented using the HLCLK bit and CKS2 ~ CKS0 bits in the SMOD register and as the system
clock can be dynamically selected.
The actual source clock used for the high speed and the low speed oscillators is chosen via
configuration options. The frequency of the slow speed or high speed system clock is also
determined using the HLCLK bit and CKS2 ~ CKS0 bits in the SMOD register. Note that two
oscillator selections must be made namely one high speed and one low speed system oscillators. It is
not possible to choose a no-oscillator selection for either the high or low speed oscillator. The OSC1
and OSC2 pins are used to connect the external components for the external crystal.
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High Speed
Osci��ation
HXT
fH
6- stage Presca�er
HIRC
fH /�
fH /4
fH /8
High Speed Osci��ation
Config�ration Option
fH /16
fH /��
fH /64
LXT
f SYS
fL
LIRC
HLCLK�
CKS�~CKS0 bits
Low Speed
Osci��ation
f SUB
Low Speed Osci��ation
Config�ration Option
Fast Wake �p from SLEEP Mode or
IDLE Mode Contro� (for HXT on��)
Note: there is not the LXT oscillator in HT66F0172
System Clock Configurations
External Crystal/Ceramic Oscillator – HXT
The External Crystal/ Ceramic System Oscillator is one of the high frequency oscillator choices,
which is selected via configuration option. For most crystal oscillator configurations, the simple
connection of a crystal across OSC1 and OSC2 will create the necessary phase shift and feedback for
oscillation, without requiring external capacitors. However, for some crystal types and frequencies,
to ensure oscillation, it may be necessary to add two small value capacitors, C1 and C2.
Using a ceramic resonator will usually require two small value capacitors, C1 and C2, to be
connected as shown for oscillation to occur. The values of C1 and C2 should be selected in
consultation with the crystal or resonator manufacturer’s specification.
     Crystal/Resonator Oscillator – HXT
Crystal Osillator C1 and C2 Values
Crystal Frequency
C1
C2
12MHz
0pF
0pF
8MHz
0pF
0pF
4MHz
0pF
0pF
1MHz
100pF
100pF
Note: C1 and C2 vales are for guidance only.
Crystal Recommended Capacitor Values
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Enhanced A/D Flash 8-Bit MCU
Internal RC Oscillator – HIRC
The internal RC oscillator is a fully integrated system oscillator requiring no external components.
The internal RC oscillator has fixed frequency of 8MHz. Device trimming during the manufacturing
process and the inclusion of internal frequency compensation circuits are used to ensure that
the influence of the power supply voltage, temperature and process variations on the oscillation
frequency are minimised. As a result, at a power supply of either 3V or 5V and at a temperature of
25˚C degrees, the fixed oscillation frequency of 8MHz will have a tolerance within 2%. Note that if
this internal system clock option is selected, as it requires no external pins for its operation, I/O pins
PC0 and PC1 are free for use as normal I/O pins
External 32.768kHz Crystal Oscillator – LXT
The External 32.768kHz Crystal System Oscillator is one of the low frequency oscillator choices,
which is selected via configuration option. This clock source has a fixed frequency of 32.768kHz
and requires a 32.768kHz crystal to be connected between pins XT1 and XT2. The external resistor
and capacitor components connected to the 32.768kHz crystal are necessary to provide oscillation.
For applications where precise frequencies are essential, these components may be required to
provide frequency compensation due to different crystal manufacturing tolerances. During power-up
there is a time delay associated with the LXT oscillator waiting for it to start-up. When the microcontroller enters the SLEEP or IDLE Mode, the system clock is switched off to stop
microcontroller activity and to conserve power. However, in many microcontroller applications
it may be necessary to keep the internal timers operational even when the microcontroller is in
the SLEEP or IDLE Mode. To do this, another clock, independent of the system clock, must be
provided.
However, for some crystals, to ensure oscillation and accurate frequency generation, it is necessary
to add two small value external capacitors, C1 and C2. The exact values of C1 and C2 should be
selected in consultation with the crystal or resonator manufacturer’s specification. The external
parallel feedback resistor, Rp, is required.
Some configuration options determine if the XT1 and XT2 pins are used for the LXT oscillator or as
I/O pins.
• If the LXT oscillator is not used for any clock source, the XT1 and XT2 pins can be used as
normal I/O pins.
• If the LXT oscillator is used for any clock source, the 32.768kHz crystal should be connected to
the XT1 and XT2 pins.
‚     
­ €
‚  External LXT Oscillator
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LXT Oscillator C1 and C2 Values
Crystal Frequency
C1
C2
32.768kHz
10pF
10pF
Note: 1. C1 and C2 values are for guidance only.
2. RP=5M~10MΩ is recommended.
32.768kHz Crystal Recommended Capacitor Values
LXT Oscillator Low Power Function
The LXT oscillator can function in one of two modes, the Quick Start Mode and the Low Power
Mode. The mode selection is executed using the LXTLP bit in the TBC register.
LXTLP Bit
LXT Mode
0
Quick Start
1
Low-power
After power on, the LXTLP bit will be automatically cleared to zero ensuring that the LXT oscillator
is in the Quick Start operating mode. In the Quick Start Mode the LXT oscillator will power up
and stabilise quickly. However, after the LXT oscillator has fully powered up it can be placed
into the Low-power mode by setting the LXTLP bit high. The oscillator will continue to run but
with reduced current consumption, as the higher current consumption is only required during the
LXT oscillator start-up. In power sensitive applications, such as battery applications, where power
consumption must be kept to a minimum, it is therefore recommended that the application program
sets the LXTLP bit high about 2 seconds after power-on.
It should be noted that, no matter what condition the LXTLP bit is set to, the LXT oscillator will
always function normally, the only difference is that it will take more time to start up if in the Lowpower mode.
Internal 32kHz Oscillator – LIRC
The Internal 32kHz System Oscillator is a low frequency oscillator choice. It is a fully integrated
RC oscillator with a typical frequency of 32kHz at 5V, requiring no external components for its
implementation. Device trimming during the manufacturing process and the inclusion of internal
frequency compensation circuits are used to ensure that the influence of the power supply voltage,
temperature and process variations on the oscillation frequency are minimised. As a result, at a
power supply of 5V and at a temperature of 25˚C degrees, the fixed oscillation frequency of 32kHz
will have a tolerance within 10%.
Supplementary Clocks
The low speed oscillators, in addition to providing a system clock source are also used to provide a
clock source to other device functions. These are the Watchdog Timer and the Time Base Interrupt.
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Operating Modes and System Clocks
Present day applications require that their microcontrollers have high performance but often still
demand that they consume as little power as possible, conflicting requirements that are especially
true in battery powered portable applications. The fast clocks required for high performance will
by their nature increase current consumption and of course vice-versa, lower speed clocks reduce
current consumption. As Holtek has provided this device with both high and low speed clock
sources and the means to switch between them dynamically, the user can optimise the operation of
their microcontroller to achieve the best performance/power ratio.
System Clocks
The device has many different clock sources for both the CPU and peripheral function operation.
By providing the user with a wide range of clock options using configuration options and register
programming, a clock system can be configured to obtain maximum application performance.
The main system clock, can come from either a high frequency, fH, or low frequency, fL, source,
and is selected using the HLCLK bit and CKS2~CKS0 bits in the SMOD register. The high
speed system clock can be sourced from either the HXT or the HIRC oscillator, selected via a
configuration option. The low speed system clock source can be sourced from either the LXT or
the LIRC oscillator, selected via a configuration option. But for HT66F0172, the low speed system
clock source can only be sourced from the LIRC oscillator. The other choice, which is a divided
version of the high speed system oscillator has a range of fH/2~fH/64.
There are two additional internal clocks for the peripheral circuits, the substitute clock, fSUB, and
the Time Base clock, fTBC. Each of these internal clocks is sourced by either the LXT or LIRC
oscillators, selected via configuration options. The fSUB clock is used to provide a substitute clock for
the microcontroller just after a wake-up has occurred to enable faster wake-up times.
High Speed
Osci��ation
HXT
fH
6- stage Presca�er
HIRC
fH /�
fH /4
fH /8
High Speed Osci��ation
Config�ration Option
fH /16
fH /��
fH /64
LXT
LIRC
Low Speed
Osci��ation
f SYS
fL
HLCLK�
CKS�~CKS0 bits
f SUB
Low Speed Osci��ation
Config�ration Option
Fast Wake- �p from SLEEP Mode or
IDLE Mode Contro� (for HXT on��)
fS
WDT
f TBC
fTB
f SYS/4
Time Base
TBCK
System Clock Configurations
Note: 1. When the system clock source fSYS is switched to fL from fH, the high speed oscillation will stop to conserve the power. Thus there is no fH~fH/64 for peripheral circuit to use.
2. There is not the LXT oscillator in HT66F0172
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System Operation Modes
There are six different modes of operation for the microcontroller, each one with its own
special characteristics and which can be chosen according to the specific performance and
power requirements of the application. There are two modes allowing normal operation of the
microcontroller, the NORMAL Mode and SLOW Mode. The remaining four modes, the SLEEP0,
SLEEP1, IDLE0 and IDLE1 Mode are used when the microcontroller CPU is switched off to
conserve power.
Operating
Mode
Description
CPU
fSYS
fSUB
fS
fTBC
NORMAL Mode
On
fH~fH/64
On
On
On
SLOW Mode
On
fL
On
On
On
IDLE0 Mode
Off
Off
On
On
On
IDLE1 Mode
Off
On
On
On
On
SLEEP0 Mode
Off
Off
Off
Off
Off
SLEEP1 Mode
Off
Off
On
On
Off
NORMAL Mode
As the name suggests this is one of the main operating modes where the microcontroller has all of
its functions operational and where the system clock is provided by one of the high speed oscillator.
This mode operates allowing the microcontroller to operate normally with a clock source will come
from the high speed oscillator, either the HXT or HIRC. The high speed oscillator will however
first be divided by a ratio ranging from 1 to 64, the actual ratio being selected by the CKS2~CKS0
and HLCLK bits in the SMOD register. Although a high speed oscillator is used, running the
microcontroller at a divided clock ratio reduces the operating current.
SLOW Mode
This is also a mode where the microcontroller operates normally although now with a slower speed
clock source. The clock source used will be from fL. Running the microcontroller in this mode
allows it to run with much lower operating currents. In the SLOW Mode, the fH is off.
SLEEP0 Mode
The SLEEP Mode is entered when an HALT instruction is executed and when the IDLEN bit in the
SMOD register is low. In the SLEEP0 mode the CPU will be stopped. And the fSUB and fS clocks will
be stopped too, and the Watchdog Timer function is disabled. In this mode, the LVDEN is must set
to "0". If the LVDEN is set to "1", it won’t enter the SLEEP0 Mode.
SLEEP1 Mode
The SLEEP Mode is entered when an HALT instruction is executed and when the IDLEN bit in
the SMOD register is low. In the SLEEP1 mode the CPU will be stopped. However the fSUB and fS
clocks will continue to operate if the LVDEN is "1" or the Watchdog Timer function is enabled.
IDLE0 Mode
The IDLE0 Mode is entered when a HALT instruction is executed and when the IDLEN bit in the
SMOD register is high and the FSYSON bit in the CTRL register is low. In the IDLE0 Mode the
system oscillator will be inhibited from driving the CPU but some peripheral functions will remain
operational such as the Watchdog Timer and TMs. In the IDLE0 Mode, the system oscillator will be
stopped.
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IDLE1 Mode
The IDLE1 Mode is entered when an HALT instruction is executed and when the IDLEN bit in the
SMOD register is high and the FSYSON bit in the CTRL register is high. In the IDLE1 Mode the
system oscillator will be inhibited from driving the CPU but may continue to provide a clock source
to keep some peripheral functions operational such as the Watchdog Timer and TMs. In the IDLE1
Mode, the system oscillator will continue to run, and this system oscillator may be high speed or low
speed system oscillator.
Control Register
A single register, SMOD, is used to overall control of the internal clocks within the device.
SMOD Register
Bit
7
6
5
4
3
2
1
0
Name
CKS2
CKS1
CKS0
FSTEN
LTO
HTO
IDLEN
HLCLK
R/W
R/W
R/W
R/W
R/W
R
R
R/W
R/W
POR
0
0
0
0
0
0
1
1
Bit 7 ~ 5
CKS2 ~ CKS0: The system clock selection when HLCLK is "0"
000: fL (fLXT or fLIRC)
001: fL(fLXT or fLIRC)
010: fH/64
011: fH/32
100: fH/16
101: fH/8
110: fH/4
111: fH/2
These three bits are used to select which clock is used as the system clock source. In
addition to the system clock source, which can be either the LXT or LIRC, a divided
version of the high speed system oscillator can also be chosen as the system clock source.
Bit 4
FSTEN: Fast Wake-up Control(only for HXT)
0: Disable
1: Enable
This is the Fast Wake-up Control bit which determines if the fSUB clock source is initially
used after the device wakes up. When the bit is high, the fSUB clock source can be used as
a temporary system clock to provide a faster wake up time as the fSUB clock is available.
Bit 3LTO: Low speed system oscillator ready flag
0: Not ready
1: Ready
This is the low speed system oscillator SST ready flag which indicates when the low
speed system oscillator is stable after power on reset or a wake-up has occurred. The
flag will be low when in the SLEEP0 Mode but after a wake-up has occurred, the flag
will change to a high level after 128 clock cycles if the LXT oscillator is used and 1~2
clock cycles if the LIRC oscillator is used.
Bit 2HTO: High speed system oscillator ready flag
0: Not ready
1: Ready
This is the high speed system oscillator SST ready flag which indicates when the high
speed system oscillator is stable after a wake-up has occurred. This flag is cleared to
"0" by hardware when the device is powered on and then changes to a high level after
the high speed system oscillator is stable. Therefore this flag will always be read as
"1" by the application program after device power-on. The flag will be low when in
the SLEEP or IDLE0 Mode but after a wake-up has occurred, the flag will change to
a high level after 128 clock cycles if the HXT oscillator is used and after 15~16 clock
cycles if the HIRC oscillator is used.
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Bit 1IDLEN: IDLE Mode Control
0: Disable
1: Enable
This is the IDLE Mode Control bit and determines what happens when the HALT
instruction is executed. If this bit is high, when a HALT instruction is executed the
device will enter the IDLE Mode. In the IDLE1 Mode the CPU will stop running
but the system clock will continue to keep the peripheral functions operational, if
FSYSON bit is high. If FSYSON bit is low, the CPU and the system clock will all stop
in IDLE0 mode. If the bit is low the device will enter the SLEEP Mode when a HALT
instruction is executed.
Bit 0HLCLK: System Clock Selection
0: fH/2 ~ fH/64 or fL
1: fH
This bit is used to select if the fH clock or the fH/2 ~ fH/64 or fL clock is used as the
system clock. When the bit is high the fH clock will be selected and if low the fH/2 ~
fH/64 or fL clock will be selected. When system clock switches from the fH clock to the
fL clock and the fH clock will be automatically switched off to conserve power.
CTRL Register
Bit
7
6
5
4
3
2
1
0
Name
FSYSON
—
—
—
—
R/W
R/W
—
—
—
—
LVRF
LRF
WRF
R/W
R/W
R/W
POR
0
—
—
—
—
x
0
0
Bit 7 FSYSON: fSYS Control in IDLE Mode
0: Disable
1: Enable
Bit 6~3
Unimplemented, read as 0.
Bit 2LVRF: LVR function reset flag
0: Not occur
1: Occurred
This bit is set to 1 when a specific Low Voltage Reset situation condition occurs. This
bit can only be cleared to 0 by the application program.
Bit 1LRF: LVRC Control register software reset flag
0: Not occur
1: Occurred
This bit is set to 1 if the LVRC register contains any non defined LVR voltage register
values. This in effect acts like a software reset function. This bit can only be cleared to
0 by the application program.
Bit 0WRF: WDT Control register software reset flag
0: Not occur
1: Occurred
This bit is set to 1 by the WDT Control register software reset and cleared by the
application program. Note that this bit can only be cleared to 0 by the application
program.
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Fast Wake-up
To minimise power consumption the device can enter the SLEEP or IDLE0 Mode, where the system
clock source to the device will be stopped. However when the device is woken up again, it can take
a considerable time for the original system oscillator to restart, stabilize and allow normal operation
to resume. To ensure the device is up and running as fast as possible a Fast Wake-up function is
provided, which allows fSUB, namely either the LXT or LIRC oscillator, to act as a temporary clock
to first drive the system until the original system oscillator has stabilised. As the clock source for
the Fast Wake-up function is fSUB, the Fast Wake-up function is only available in the SLEEP1 and
IDLE0 modes. When the device is woken up from the SLEEP0 mode, the Fast Wake-up function has
no effect because the fSUB clock is stopped. The Fast Wake-up enable/disable function is controlled
using the FSTEN bit in the SMOD register.
If the HXT oscillator is selected as the NORMAL Mode system clock, and if the Fast Wake-up
function is enabled, then it will take one to two tSUB clock cycles of the LIRC or LXT oscillator for
the system to wake-up. The system will then initially run under the fSUB clock source until 128 HXT
clock cycles have elapsed, at which point the HTO flag will switch high and the system will switch
over to operating from the HXT oscillator.
If the HIRC oscillators or LIRC oscillator is used as the system oscillator then it will take 15~16
clock cycles of HIRC or 1~2 cycles of the LIRC to wake up the system from the SLEEP or IDLE0
Mode. The Fast Wake-up bit, FSTEN will have no effect in these cases.
System FSTEN
Oscillator
Bit
HXT
Wake-up Time
(SLEEP0 Mode)
Wake-up Time
(SLEEP1 Mode)
Wake-up Time
(IDLE0 Mode)
Wake-up Time
(IDLE1 Mode)
0
128 HXT cycles
128 HXT cycles
1~2 HXT cycles
1
128 HXT cycles
1~2 fSUB cycles
(System runs with fSUB first for 128 HXT cycles and
then switches over to run with the HXT clock)
1~2 HXT cycles
HIRC
X
15~16 HIRC cycles 15~16 HIRC cycles
1~2 HIRC cycles
LIRC
X
1~2 LIRC cycles
1~2 LIRC cycles
1~2 LIRC cycles
LXT
X
128 LTX cycles
1~2 LXT cycles
1~2 LXT cycles
Wake-Up Times
Note that if the Watchdog Timer is disabled, which means that the LXT and LIRC are both off, then
there will be no Fast Wake-up function available when the device wakes-up from the SLEEP0 Mode.
Operating Mode Switching
The device can switch between operating modes dynamically allowing the user to select the best
performance/power ratio for the present task in hand. In this way microcontroller operations that
do not require high performance can be executed using slower clocks thus requiring less operating
current and prolonging battery life in portable applications.
In simple terms, Mode Switching between the NORMAL Mode and SLOW Mode is executed using the
HLCLK bit and CKS2~CKS0 bits in the SMOD register while Mode Switching from the NORMAL/
SLOW Modes to the SLEEP/IDLE Modes is executed via the HALT instruction. When a HALT
instruction is executed, whether the device enters the IDLE Mode or the SLEEP Mode is determined by
the condition of the IDLEN bit in the SMOD register and FSYSON in the WDTC register.
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When the HLCLK bit switches to a low level, which implies that clock source is switched from the
high speed clock source, fH, to the clock source, fH/2~fH/64 or fL. If the clock is from the fL, the high
speed clock source will stop running to conserve power. When this happens it must be noted that the
fH/16 and fH/64 internal clock sources will also stop running, which may affect the operation of other
internal functions such as the TMs. The accompanying flowchart shows what happens when the
device moves between the various operating modes.
­ €   
­ €    NORMAL Mode to SLOW Mode Switching
When running in the NORMAL Mode, which uses the high speed system oscillator, and therefore
consumes more power, the system clock can switch to run in the SLOW Mode by setting the
HLCLK bit to "0" and setting the CKS2~CKS0 bits to "000" or "001" in the SMOD register. This
will then use the low speed system oscillator which will consume less power. Users may decide to
do this for certain operations which do not require high performance and can subsequently reduce
power consumption.
The SLOW Mode is sourced from the LIRC or the LXT oscillator and therefore requires these
oscillators to be stable before full mode switching occurs. This is monitored using the LTO bit in the
SMOD register.
SLOW Mode to NORMAL Mode Switching
In SLOW Mode the system uses either the LXT or LIRC low speed system oscillator. To switch
back to the NORMAL Mode, where the high speed system oscillator is used, the HLCLK bit should
be set to "1" or HLCLK bit is "0", but CKS2~CKS0 is set to "010", "011", "100", "101", "110" or
"111". As a certain amount of time will be required for the high frequency clock to stabilise, the
status of the HTO bit is checked. The amount of time required for high speed system oscillator
stabilization depends upon which high speed system oscillator type is used.
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Enhanced A/D Flash 8-Bit MCU
  
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Enhanced A/D Flash 8-Bit MCU
Entering the SLEEP0 Mode
There is only one way for the device to enter the SLEEP0 Mode and that is to execute the "HALT"
instruction in the application program with the IDLEN bit in SMOD register equal to "0" and the
WDT and LVD both off. When this instruction is executed under the conditions described above, the
following will occur:
• The system clock, WDT clock and Time Base clock will be stopped and the application program
will stop at the "HALT" instruction.
• The Data Memory contents and registers will maintain their present condition.
• The WDT will be cleared and stopped.
• The I/O ports will maintain their present conditions.
• In the status register, the Power Down flag, PDF, will be set and the Watchdog time-out flag, TO,
will be cleared.
Entering the SLEEP1 Mode
There is only one way for the device to enter the SLEEP1 Mode and that is to execute the "HALT"
instruction in the application program with the IDLEN bit in SMOD register equal to "0" and the
WDT or LVD on. When this instruction is executed under the conditions described above, the
following will occur:
• The system clock and Time Base clock will be stopped and the application program will stop at
the "HALT" instruction, but the WDT or LVD will remain with the clock source coming from the
fSUB clock.
• The Data Memory contents and registers will maintain their present condition.
• The WDT will be cleared and resume counting if the WDT is enabled.
• The I/O ports will maintain their present conditions.
• In the status register, the Power Down flag, PDF, will be set and the Watchdog time-out flag, TO,
will be cleared.
Entering the IDLE0 Mode
There is only one way for the device to enter the IDLE0 Mode and that is to execute the "HALT"
instruction in the application program with the IDLEN bit in SMOD register equal to "1" and the
FSYSON bit in CTRL register equal to "0". When this instruction is executed under the conditions
described above, the following will occur:
• The system clock will be stopped and the application program will stop at the "HALT" instruction, but the Time Base clock fTBC and fSUB clock will be on.
• The Data Memory contents and registers will maintain their present condition.
• The WDT will be cleared and resume counting if the WDT is enabled.
• The I/O ports will maintain their present conditions.
• In the status register, the Power Down flag, PDF, will be set and the Watchdog time-out flag, TO,
will be cleared.
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Entering the IDLE1 Mode
There is only one way for the device to enter the IDLE1 Mode and that is to execute the "HALT"
instruction in the application program with the IDLEN bit in SMOD register equal to "1" and the
FSYSON bit in CTRL register equal to "1". When this instruction is executed under the conditions
described above, the following will occur:
• The system clock and Time Base clock and fSUB clock will be on and the application program will
stop at the "HALT" instruction.
• The Data Memory contents and registers will maintain their present condition.
• The WDT will be cleared and resume counting if the WDT is enabled
• The I/O ports will maintain their present conditions.
• In the status register, the Power Down flag, PDF, will be set and the Watchdog time-out flag, TO,
will be cleared.
Standby Current Considerations
As the main reason for entering the SLEEP or IDLE Mode is to keep the current consumption of the
device to as low a value as possible, perhaps only in the order of several micro-amps except in the
IDLE1 Mode, there are other considerations which must also be taken into account by the circuit
designer if the power consumption is to be minimised. Special attention must be made to the I/O pins
on the device. All high-impedance input pins must be connected to either a fixed high or low level as
any floating input pins could create internal oscillations and result in increased current consumption.
This also applies to the device which has different package types, as there may be unbonbed pins.
These must either be setup as outputs or if setup as inputs must have pull-high resistors connected.
Care must also be taken with the loads, which are connected to I/O pins, which are setup as outputs.
These should be placed in a condition in which minimum current is drawn or connected only to
external circuits that do not draw current, such as other CMOS inputs. Also note that additional
standby current will also be required if the configuration options have enabled the LXT or LIRC
oscillator.
In the IDLE1 Mode the system oscillator is on, if the system oscillator is from the high speed system
oscillator, the additional standby current will also be perhaps in the order of several hundred microamps.
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Wake-up
After the system enters the SLEEP or IDLE Mode, it can be woken up from one of various sources
listed as follows:
• An external falling edge on Port A
• A system interrupt
• A WDT overflow
If the system is woken up by an external reset, the device will experience a full system reset,
however, if the device is woken up by a WDT overflow, a Watchdog Timer reset will be initiated.
Although both of these wake-up methods will initiate a reset operation, the actual source of the
wake-up can be determined by examining the TO and PDF flags. The PDF flag is cleared by a
system power-up or executing the clear Watchdog Timer instructions and is set when executing the
"HALT" instruction. The TO flag is set if a WDT time-out occurs, and causes a wake-up that only
resets the Program Counter and Stack Pointer, the other flags remain in their original status.
Each pin on Port A can be setup using the PAWU register to permit a negative transition on the pin
to wake-up the system. When a Port A pin wake-up occurs, the program will resume execution at
the instruction following the "HALT" instruction. If the system is woken up by an interrupt, then
two possible situations may occur. The first is where the related interrupt is disabled or the interrupt
is enabled but the stack is full, in which case the program will resume execution at the instruction
following the "HALT" instruction. In this situation, the interrupt which woke-up the device will not
be immediately serviced, but will rather be serviced later when the related interrupt is finally enabled
or when a stack level becomes free. The other situation is where the related interrupt is enabled and
the stack is not full, in which case the regular interrupt response takes place. If an interrupt request
flag is set high before entering the SLEEP or IDLE Mode, the wake-up function of the related
interrupt will be disabled.
Programming Considerations
The high speed and low speed oscillators both use the same SST counter. For example, if the system
is woken up from the SLEEP0 Mode and both the HIRC and LXT oscillators need to start-up from
an off state. The LXT oscillator uses the SST counter after HIRC oscillator has finished its SST
period.
• If the device is woken up from the SLEEP0 Mode to the NORMAL Mode, the high speed system
oscillator needs an SST period. The device will execute first instruction after HTO is "1". At this
time, the LXT oscillator may not be stability if fSUB is from LXT oscillator. The same situation
occurs in the power-on state. The LXT oscillator is not ready yet when the first instruction is
executed.
• If the device is woken up from the SLEEP1 Mode to NORMAL Mode, and the system clock
source is from HXT oscillator and FSTEN is "1", the system clock can be switched to the LIRC
oscillator after wake up.
• There are peripheral functions for which the fSYS is used. If the system clock source is switched
from fH to fL, the clock source to the peripheral functions mentioned above will change accordingly.
• The on/off condition of fS depends upon whether the WDT is enabled or disabled as the WDT
clock source is selected from fS.
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Watchdog Timer
The Watchdog Timer is provided to prevent program malfunctions or sequences from jumping to
unknown locations, due to certain uncontrollable external events such as electrical noise.
Watchdog Timer Clock Source
The Watchdog Timer clock source is provided by the internal fs clock which is sourced from LXT
or LIRC oscillator chosen via a configuration option. The Watchdog Timer source clock is then
subdivided by a ratio of 28 to 218 to give longer timeouts, the actual value being chosen using the
WS2~WS0 bits in the WDTC register. The LXT oscillator is supplied by an external 32.768kHz
crystal. The LIRC internal oscillator has an approximate period of 32kHz at a supply voltage of 5V.
However, it should be noted that this specified internal clock period can vary with VDD, temperature
and process variations.
Note that the Watchdog Timer function is controlled by application program and is allowed to enable
or disable WDT by application program.
Watchdog Timer Control Register
A single register, WDTC, controls the required timeout period as well as the enable or disable
operation. This register controls the overall operation of the Watchdog Timer.
WDTC Register
Rev. 1.00
Bit
7
6
5
4
3
2
1
0
Name
WE4
WE3
WE2
WE1
WE0
WS2
WS1
WS0
R/W
R/W
R/W
R/W
R/W
R/W
R/W
R/W
R/W
POR
0
1
0
1
0
0
1
1
Bit 7~ 3
WE4 ~ WE0: WDT function software control
10101: Disabled
01010: Enabled
Other: Reset MCU
When these bits are changed by the environmental noise to reset the microcontroller,
the reset operation will be activated after 2~3 LIRC clock cycles and the WRF bit in
the CTRL register will be set to 1.
Bit 2~ 0
WS2 ~ WS0: WDT Time-out period selection
000: 28/fS
001: 210/fS
010: 212/fS
011: 214/fS
100: 215/fS
101: 216/fS
110: 217/fS
111: 218/fS
These three bits determine the division ratio of the Watchdog Timer source clock,
which in turn determines the timeout period.
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CTRL Register
Bit
7
6
5
4
3
2
1
0
Name
FSYSON
—
—
—
—
LVRF
LRF
WRF
R/W
R/W
—
—
—
—
R/W
R/W
R/W
POR
0
—
—
—
—
×
0
0
Bit 7FSYSON: fSYS Control in IDLE Mode
Describe elsewhere
Bit 6~ 3
Unimplemented, read as "0"
Bit 2
LVRF: LVR function reset flag
Describe elsewhere
Bit 1
LRF: LVR Control register software reset flag
Describe elsewhere
Bit 0
WRF: WDT Control register software reset flag
0: Not occur
1: Occurred
This bit is set to 1 by the WDT Control register software reset and cleared by the
application program. Note that this bit can only be cleared to 0 by the application
program.
Watchdog Timer Operation
The Watchdog Timer operates by providing a device reset when its timer overflows. This means
that in the application program and during normal operation the user has to strategically clear the
Watchdog Timer before it overflows to prevent the Watchdog Timer from executing a reset. This is
done using the clear watchdog instructions. If the program malfunctions for whatever reason, jumps
to an unknown location, or enters an endless loop, the clear WDT instruction will not be executed
in the correct manner, in which case the Watchdog Timer will overflow and reset the device. With
regard to the Watchdog Timer enable/disable function, there are five bits, WE4~WE0, in the WDTC
register to offer additional enable or disable and reset control of the Watchdog Timer. The WDT
function will be disabled when the WE4~WE0 bits are set to a value of 10101B. The WDT function
will be enabled if the WE4~WE0 bits value is equal to 01010B. If the WE4~WE0 bits are set to any
other values by the environmental noise, except 01010B and 10101B, it will reset the device after 2~3
LIRC clock cycles. After power on these bits will have the value of 01010B.
WDT Function Control
WE4 ~ WE0 Bits
WDT Function
10101B
Disable
01010B
Enable
Any other value
Reset MCU
Application Program Enabled
Watchdog Timer Enable/Disable Control
Under normal program operation, a Watchdog Timer time-out will initialise a device reset and set
the status bit TO. However, if the system is in the SLEEP or IDLE Mode, when a Watchdog Timer
time-out occurs, the TO bit in the status register will be set and only the Program Counter and Stack
Pointer will be reset. Several methods can be adopted to clear the contents of the Watchdog Timer.
The first is a WDT software reset, which means a certain value is written into the WE4~WE0 bit
field except 01010B and 10101B, the second is using the Watchdog Timer software clear instruction
and the third is via a HALT instruction.
There is only one method of using software instruction to clear the Watchdog Timer. That is to use
the single "CLR WDT" instruction to clear the WDT.
Rev. 1.00
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The maximum time-out period is when the 218 division ratio is selected. As an example, with a 32 kHz
LIRC oscillator as its source clock, this will give a maximum watchdog period of around 8 seconds for
the 218 division ratio, and a minimum timeout of 7.8ms for the 28 division ration.
WDTC Register
WE4~WE0 bits
Reset MCU
CLR
“HALT”Instr�ction
“CLR WDT”Instr�ction
LXT
LIRC
M
U
X
fS
8-stage Divider
Low Speed Osci��ator
Config�ration option
fS/�8
WDT Presca�er
WS�~WS0
(fS/�8 ~ fS/�18)
8-to-1 MUX
WDT Time-o�t
(�8/fS ~ �18/fS)
Watchdog Timer
Reset and Initialisation
A reset function is a fundamental part of any microcontroller ensuring that the device can be set
to some predetermined condition irrespective of outside parameters. The most important reset
condition is after power is first applied to the microcontroller. In this case, internal circuitry will
ensure that the microcontroller, after a short delay, will be in a well defined state and ready to
execute the first program instruction. After this power-on reset, certain important internal registers
will be set to defined states before the program commences. One of these registers is the Program
Counter, which will be reset to zero forcing the microcontroller to begin program execution from the
lowest Program Memory address.
Another type of reset is when the Watchdog Timer overflows and resets the microcontroller. All
types of reset operations result in different register conditions being setup. Another reset exists in the
form of a Low Voltage Reset, LVR, where a full reset is implemented in situations where the power
supply voltage falls below a certain threshold.
Reset Functions
There are more than one way in which the microcontroller can be reset, each of which will be
described as follows.
Power-on Reset
The most fundamental and unavoidable reset is the one that occurs after power is first applied to
the microcontroller. As well as ensuring that the Program Memory begins execution from the first
memory address, a power-on reset also ensures that certain other registers are preset to known
conditions. All the I/O port and port control registers will power up in a high condition ensuring that
all pins will be first set to inputs.
Power-On Reset Timing Chart
Rev. 1.00
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Low Voltage Reset – LVR
The microcontroller contains a low voltage reset circuit in order to monitor the supply voltage of the
device. The LVR function is always enabled with a specific LVR voltage, VLVR. If the supply voltage
of the device drops to within a range of 0.9V~VLVR such as might occur when changing the battery,
the LVR will automatically reset the device internally and the LVRF bit in the CTRL register will
also be set to 1. For a valid LVR signal, a low voltage, i.e., a voltage in the range between 0.9V~
VLVR must exist for greater than the value tLVR specified in the LVD&LVR characteristics. If the low
voltage state does not exceed this value, the LVR will ignore the low supply voltage and will not
perform a reset function.
The actual V LVR value can be selected by the LVS7~LVS0 bits in the LVRC register. If the
LVS7~LVS0 bits are changed to some certain values by the environmental noise or software setting,
the LVR will reset the device after 2~3 LIRC clock cycles. When this happens, the LRF bit in the
CTRL register will be set to 1. After power on the register will have the value of 01010101B. Note
that the LVR function will be automatically disabled when the device enters the power down mode.
Low Voltage Reset Timing Chart
• LVRC Register
Bit
7
6
5
4
3
2
1
0
Name
LVS7
LVS6
LVS5
LVS4
LVS3
LVS2
LVS1
LVS0
R/W
R/W
R/W
R/W
R/W
R/W
R/W
R/W
R/W
POR
0
1
0
1
0
1
0
1
Bit 7 ~ 0
LVS7 ~ LVS0: LVR Voltage Select control
01010101: 2.1V
00110011: 2.55V
10011001: 3.15V
10101010: 3.8V
Any other value: generates MCU reset – register is reset to POR value
When an actual low voltage condition occurs, as specified by one of the four defined
LVR voltage values above, an MCU reset will be generated. The reset operation will be
activated after 2~3 LIRC clock cycles. In this situation the register contents will remain the
same after such a reset occurs.
Any register value, other than the four defined LVR values above, will also result in
the generation of an MCU reset. The reset operation will be activated after 2~3 LIRC
clock cycles. However in this situation the register contents will be reset to the POR
value.
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• CTRL Register
Bit
7
6
5
4
3
2
Name
FSYSON
—
—
—
—
R/W
R/W
—
—
—
—
POR
0
—
—
—
—
Bit 7
FSYSON: fSYS Control IDLE Mode
Describe elsewhere
Bit 6~ 3
Unimplemented, read as "0"
1
0
LVRF
LRF
WRF
R/W
R/W
R/W
×
0
0
Bit 2LVRF: LVR function reset flag
0: Not occur
1: Occurred
This bit is set to 1 when a specific Low Voltage Reset situation condition occurs. This
bit can only be cleared to 0 by the application program.
Bit 1LRF: LVR Control register software reset flag
0: Not occur
1: Occurred
This bit is set to 1 if the LVRC register contains any non defined LVR voltage register
values. This in effect acts like a software reset function. This bit can only be cleared to
0 by the application program.
Bit 0WRF: WDT Control register software reset flag
Describe elsewhere
Watchdog Time-out Reset during Normal Operation
The Watchdog time-out Reset during normal operation is the same as a hardware LVR reset except
that the Watchdog time-out flag TO will be set to "1".
WDT Time-out Reset during Normal Operation Timing Chart
Watchdog Time-out Reset during SLEEP or IDLE Mode
The Watchdog time-out Reset during SLEEP or IDLE Mode is a little different from other kinds
of reset. Most of the conditions remain unchanged except that the Program Counter and the Stack
Pointer will be cleared to "0" and the TO flag will be set to "1". Refer to the A.C. Characteristics for
tSST details.
WDT Time-out Reset during SLEEP or IDLE Timing Chart
Rev. 1.00
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Reset Initial Conditions
The different types of reset described affect the reset flags in different ways. These flags, known
as PDF and TO are located in the status register and are controlled by various microcontroller
operations, such as the SLEEP or IDLE Mode function or Watchdog Timer. The reset flags are
shown in the table:
TO
PDF
RESET Conditions
0
0
Power-on reset
u
u
LVR reset during NORMAL or SLOW Mode operation
1
u
WDT time-out reset during NORMAL or SLOW Mode operation
1
1
WDT time-out reset during IDLE or SLEEP Mode operation
Note: "u" stands for unchanged
The following table indicates the way in which the various components of the microcontroller are
affected after a power-on reset occurs.
Item
Condition After RESET
Program Counter
Reset to zero
Interrupts
All interrupts will be disabled
WDT
Clear after reset, WDT begins counting
Timer Modules
Timer Modules will be turned off
Input/Output Ports
I/O ports will be setup as inputs
Stack Pointer
Stack Pointer will point to the top of the stack
The different kinds of resets all affect the internal registers of the microcontroller in different ways.
To ensure reliable continuation of normal program execution after a reset occurs, it is important to
know what condition the microcontroller is in after a particular reset occurs. The following table
describes how each type of reset affects each of the microcontroller internal registers.
Power On
Reset
LVR Reset
WDT Time-out
(Normal Operation)
WDT Time-out
(SLEEP/IDLE)
MP0
xxxx xxxx
xxxx xxxx
xxxx xxxx
uuuu uuuu
MP1
xxxx xxxx
xxxx xxxx
xxxx xxxx
uuuu uuuu
BP
---- ---0
---- ---0
---- ---0
---- ---u
ACC
xxxx xxxx
uuuu uuuu
uuuu uuuu
uuuu uuuu
PCL
0000 0000
0000 0000
0000 0000
0000 0000
TBLP
xxxx xxxx
uuuu uuuu
uuuu uuuu
uuuu uuuu
TBLH
xxxx xxxx
uuuu uuuu
uuuu uuuu
uuuu uuuu
TBHP
---- -xxx
- - - - - uuu
- - - - - uuu
- - - - - uuu
STATUS
--00 xxxx
- - uu x x x x
- - 1 u uuuu
- - 1 1 uuuu
SMOD
0 0 0 0 0 0 11
0 0 0 0 0 0 11
0 0 0 0 0 0 11
uuuu uuuu
LVDC
--00 -000
--00 -000
--00 -000
- - uu – uuu
INTEG
---- 0000
---- 0000
---- 0000
- - - - uuuu
INTC0
-0-0 0-00
-0-0 0-00
-0-0 0-00
- u - u u - uu
INTC1
0000 0000
0000 0000
0000 0000
uuuu uuuu
INTC2
--00 --00
--00 --00
--00 --00
- - uu - - uu
MFI0
--00 --00
--00 --00
--00 --00
- - uu - - uu
MFI1
--00 --00
--00 --00
--00 --00
- - uu - - uu
MFI2
--00 --00
--00 --00
--00 --00
- - uu - - uu
Register
Rev. 1.00
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Power On
Reset
LVR Reset
WDT Time-out
(Normal Operation)
WDT Time-out
(SLEEP/IDLE)
PA
1111 1111
1111 1111
1111 1111
uuuu uuuu
PAC
1111 1111
1111 1111
1111 1111
uuuu uuuu
PAPU
0000 0000
0000 0000
0000 0000
uuuu uuuu
PAWU
0000 0000
0000 0000
0000 0000
uuuu uuuu
TMPC
0--- --00
0--- --00
0--- --00
u - - - - - uu
WDTC
0 1 0 1 0 0 11
0 1 0 1 0 0 11
0 1 0 1 0 0 11
uuuu uuuu
TBC
0 0 11 0 111
0 0 11 0 111
0 0 11 0 111
0 0 11 0 111
EEA
--00 0000
--00 0000
--00 0000
- - uu uuuu
EED
0000 0000
0000 0000
0000 0000
uuuu uuuu
ADRL(ADRFS=0)
xxxx ----
xxxx ----
xxxx ----
uuuu - - - -
ADRL(ADRFS=1)
xxxx xxxx
xxxx xxxx
xxxx xxxx
uuuu uuuu
ADRH(ADRFS=0)
xxxx xxxx
xxxx xxxx
xxxx xxxx
uuuu uuuu
ADRH(ADRFS=1)
---- xxxx
---- xxxx
---- xxxx
- - - - uuuu
ADCR0
0 11 0 - 0 0 0
0 11 0 - 0 0 0
0 11 0 - 0 0 0
uuu u - uuu
ADCR1
00-0 -000
00-0 -000
00-0 -000
uu - u - uuu
ACERL
1111 1111
1111 1111
1111 1111
uuuu uuuu
CTRL
0--- -x00
0--- -000
0--- -000
u - - - - uuu
LVRC
0101 0101
0101 0101
0101 0101
uuuu uuuu
TM0C0
0000 0---
0000 0---
0000 0---
uuuu u - - -
TM0C1
0000 0000
0000 0000
0000 0000
uuuu uuuu
TM0DL
0000 0000
0000 0000
0000 0000
uuuu uuuu
TM0DH
0000 0000
0000 0000
0000 0000
uuuu uuuu
TM0AL
0000 0000
0000 0000
0000 0000
uuuu uuuu
TM0AH
0000 0000
0000 0000
0000 0000
uuuu uuuu
TM0RPL
0000 0000
0000 0000
0000 0000
uuuu uuuu
TM0RPH
0000 0000
0000 0000
0000 0000
uuuu uuuu
TM1C0
0000 0---
0000 0---
0000 0---
uuuu u - - -
TM1C1
0000 0000
0000 0000
0000 0000
uuuu uuuu
TM1DL
0000 0000
0000 0000
0000 0000
uuuu uuuu
TM1DH
---- --00
---- --00
---- --00
- - - - - - uu
TM1AL
0000 0000
0000 0000
0000 0000
uuuu uuuu
TM1AH
---- --00
---- --00
---- --00
- - - - - - uu
TM1RPL
0000 0000
0000 0000
0000 0000
uuuu uuuu
TM1RPH
---- --00
---- --00
---- --00
- - - - - - uu
PC
- - - - - 111
- - - - - 111
- - - - - 111
- - - - - uuu
PCC
- - - - - 111
- - - - - 111
- - - - - 111
- - - - - uuu
PCPU
---- -000
---- -000
---- -000
- - - - - uuu
PB
- 111 1111
- 111 1111
- 111 1111
- uuu uuuu
PBC
- 111 1111
- 111 1111
- 111 1111
- uuu uuuu
PBPU
-000 0000
-000 0000
-000 0000
- uuu uuuu
EEC
---- 0000
---- 0000
---- 0000
- - - - uuuu
Register
Note: "-" stands for "unimplemented"
"u" stands for "unchanged"
"x" stands for "unknown"
Rev. 1.00
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Input/Output Ports
Holtek microcontrollers offer considerable flexibility on their I/O ports. With the input or output
designation of every pin fully under user program control, pull-high selections for all ports and
wake-up selections on certain pins, the user is provided with an I/O structure to meet the needs of a
wide range of application possibilities.
The device provides bidirectional input/output lines labeled with port names PA, PB and PC. These
I/O ports are mapped to the RAM Data Memory with specific addresses as shown in the Special
Purpose Data Memory table. All of these I/O ports can be used for input and output operations. For
input operation, these ports are non-latching, which means the inputs must be ready at the T2 rising
edge of instruction "MOV A, [m]", where m denotes the port address. For output operation, all the
data is latched and remains unchanged until the output latch is rewritten.
Bit
Register
Name
7
6
5
4
3
2
1
0
PA
D7
D6
D5
D4
D3
D2
D1
D0
PAC
D7
D6
D5
D4
D3
D2
D1
D0
PAPU
D7
D6
D5
D4
D3
D2
D1
D0
PAWU
D7
D6
D5
D4
D3
D2
D1
D0
PB
—
D6
D5
D4
D3
D2
D1
D0
PBC
—
D6
D5
D4
D3
D2
D1
D0
PBPU
—
D6
D5
D4
D3
D2
D1
D0
PC
—
—
—
—
—
D2
D1
D0
PCC
—
—
—
—
—
D2
D1
D0
PCPU
—
—
—
—
—
D2
D1
D0
I/O Register List
Pull-high Resistors
Many product applications require pull-high resistors for their switch inputs usually requiring the
use of an external resistor. To eliminate the need for these external resistors, all I/O pins, when
configured as an input have the capability of being connected to an internal pull-high resistor. These
pull-high resistors are selected using registers PAPU~PCPU, and are implemented using weak
PMOS transistors.
PAPU Register
Bit
7
6
5
4
3
2
1
0
Name
D7
D6
D5
D4
D3
D2
D1
D0
R/W
R/W
R/W
R/W
R/W
R/W
R/W
R/W
R/W
POR
0
0
0
0
0
0
0
0
Bit 7 ~ 0
Rev. 1.00
I/O Port A bit7~ bit 0 Pull-High Control
0: Disable
1: Enable
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PBPU Register
Bit
7
6
5
4
3
2
1
0
Name
—
D6
D5
D4
D3
D2
D1
D0
R/W
—
R/W
R/W
R/W
R/W
R/W
R/W
R/W
POR
—
0
0
0
0
0
0
0
Bit 7
Unimplemented, read as "0"
Bit 6 ~ 0
I/O Port B bit6~ bit 0 Pull-High Control
0: Disable
1: Enable
PCPU Register
Bit
7
6
5
4
3
2
1
0
Name
—
—
—
—
—
D2
D1
D0
R/W
—
—
—
—
—
R/W
R/W
R/W
POR
—
—
—
—
—
0
0
0
Bit 7 ~ 3
Unimplemented, read as "0"
Bit 2 ~ 0
I/O Port C bit2~ bit 0 Pull-High Control
0: Disable
1: Enable
Port A Wake-up
The HALT instruction forces the microcontroller into the SLEEP or IDLE Mode which preserves
power, a feature that is important for battery and other low-power applications. Various methods
exist to wake-up the microcontroller, one of which is to change the logic condition on one of the Port
A pins from high to low. This function is especially suitable for applications that can be woken up
via external switches. Each pin on Port A can be selected individually to have this wake-up feature
using the PAWU register.
PAWU Register
Bit
7
6
5
4
3
2
1
0
Name
D7
D6
D5
D4
D3
D2
D1
D0
R/W
R/W
R/W
R/W
R/W
R/W
R/W
R/W
R/W
POR
0
0
0
0
0
0
0
0
Bit 7 ~ 0
Rev. 1.00
I/O Port A bit 7 ~ bit 0 Wake Up Control
0: Disable
1: Enable
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I/O Port Control Registers
Each I/O port has its own control register known as PAC~PCC, to control the input/output
configuration. With this control register, each CMOS output or input can be reconfigured
dynamically under software control. Each pin of the I/O ports is directly mapped to a bit in its
associated port control register. For the I/O pin to function as an input, the corresponding bit of the
control register must be written as a "1". This will then allow the logic state of the input pin to be
directly read by instructions. When the corresponding bit of the control register is written as a "0",
the I/O pin will be setup as a CMOS output. If the pin is currently setup as an output, instructions
can still be used to read the output register.
However, it should be noted that the program will in fact only read the status of the output data latch
and not the actual logic status of the output pin.
PAC Register
Bit
7
6
5
4
3
2
1
0
Name
D7
D6
D5
D4
D3
D2
D1
D0
R/W
R/W
R/W
R/W
R/W
R/W
R/W
R/W
R/W
POR
1
1
1
1
1
1
1
1
Bit 7 ~ 0
I/O Port A bit 7 ~ bit 0 Input/Output Control
0: Output
1: Input
PBC Register
Bit
7
6
5
4
3
2
1
0
Name
—
D6
D5
D4
D3
D2
D1
D0
R/W
—
R/W
R/W
R/W
R/W
R/W
R/W
R/W
POR
—
1
1
1
1
1
1
1
2
1
0
Bit 7
Bit 6 ~ 0
Unimplemented, read as "0"
I/O Port B bit6 ~ bit 0 Input/Output Control
0: Output
1: Input
PCC Register
Bit
7
6
5
4
3
Name
—
—
—
—
—
D2
D1
D0
R/W
—
—
—
—
—
R/W
R/W
R/W
POR
—
—
—
—
—
1
1
1
Bit 7 ~ 3
Bit 2 ~ 0
Rev. 1.00
Unimplemented, read as "0"
I/O Port C bit 2~bit 0 Input/Output Control
0: Output
1: Input
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I/O Pin Structures
The accompanying diagrams illustrate the internal structures of some generic I/O pin types. As
the exact logical construction of the I/O pin will differ from these drawings, they are supplied as a
guide only to assist with the functional understanding of the I/O pins. The wide range of pin-shared
structures does not permit all types to be shown.

 
    
Generic Input/Output Structure
€
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€
‚
€
‚
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A/D Input/Output Structure
Rev. 1.00
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Enhanced A/D Flash 8-Bit MCU
Programming Considerations
Within the user program, one of the first things to consider is port initialisation. After a reset, all of
the I/O data and port control registers will be set high. This means that all I/O pins will default to
an input state, the level of which depends on the other connected circuitry and whether pull-high
selections have been chosen. If the port control registers, PAC~PCC, are then programmed to setup
some pins as outputs, these output pins will have an initial high output value unless the associated
port data registers, PA~PC, are first programmed. Selecting which pins are inputs and which are
outputs can be achieved byte-wide by loading the correct values into the appropriate port control
register or by programming individual bits in the port control register using the "SET [m].i" and
"CLR [m].i" instructions. Note that when using these bit control instructions, a read-modify-write
operation takes place. The microcontroller must first read in the data on the entire port, modify it to
the required new bit values and then rewrite this data back to the output ports.
The power-on reset condition of the A/D converter control registers ensures that any A/D input pins
- which are always shared with other I/O functions - will be setup as analog inputs after a reset.
Although these pins will be configured as A/D inputs after a reset, the A/D converter will not be
switched on. It is therefore important to note that if it is required to use these pins as I/O digital
input pins or as other functions, the A/D converter control registers must be correctly programmed
to remove the A/D function. Note also that as the A/D channel is enabled, any internal pull-high
resistor connections will be removed.
Port A has the additional capability of providing wake-up functions. When the device is in the
SLEEP or IDLE Mode, various methods are available to wake the device up. One of these is a high
to low transition of any of the Port A pins. Single or multiple pins on Port A can be setup to have this
function.
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Timer Modules – TM
One of the most fundamental functions in any microcontroller device is the ability to control and
measure time. To implement time related functions the device includes several Timer Modules,
abbreviated to the name TM. The TMs are multi-purpose timing units and serve to provide
operations such as Timer/Counter, Input Capture, Compare Match Output and Single Pulse Output
as well as being the functional unit for the generation of PWM signals. Each of the TMs has two
individual interrupts. The addition of input and output pins for each TM ensures that users are
provided with timing units with a wide and flexible range of features.
The common features of the TM type are described here with more detailed information provided in
the individual Periodic Type TM section.
Introduction
The device contains two TMs having a reference name of TM0 and TM1. Both of them are Periodic
Type TM. The main features are summarised in the accompanying table.
Function
PTM
Timer/Counter
√
I/P Capture
√
Compare Match Output
√
PWM Channels
1
Single Pulse Output
1
PWM Alignment
Edge
PWM Adjustment Period & Duty
Duty or Period
PTM Function Summary
TM0
TM1
10-bit PTM
10-bit PTM
TM Name/Type Reference
TM Operation
The type of TMs offers a diverse range of functions, from simple timing operations to PWM signal
generation. The key to understanding how the TM operates is to see it in terms of a free running
counter whose value is then compared with the value of pre-programmed internal comparators.
When the free running counter has the same value as the pre-programmed comparator, known as a
compare match situation, a TM interrupt signal will be generated which can clear the counter and
perhaps also change the condition of the TM output pin. The internal TM counter is driven by a user
selectable clock source, which can be an internal clock or an external pin.
TM Clock Source
The clock source which drives the main counter in each TM can originate from various sources.
The selection of the required clock source is implemented using the TnCK2~TnCK0 bits in the TM
control registers. The clock source can be a ratio of either the system clock fSYS or the internal high
clock fH, the fTBC clock source or the external TCKn pin. The TCKn pin clock source is used to allow
an external signal to drive the TM as an external clock source or for event counting.
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TM Interrupts
The type of TMs has two internal interrupts, the internal comparator A or comparator P, which
generate a TM interrupt when a compare match condition occurs. When a TM interrupt is generated,
it can be used to clear the counter and also to change the state of the TM output pin. TM External Pins
Each of the TMs has one TM input pin, with the label TCKn. The TM input pin, is essentially a
clock source for the TM and is selected using the TnCK2~TnCK0 bits in the TMnC0 register. This
external TM input pin allows an external clock source to drive the internal TM. This external TM
input pin is shared with other functions but will be connected to the internal TM if selected using the
TnCK2~TnCK0 bits. The TM input pin can be chosen to have either a rising or falling active edge.
The TMs each have an output pin. When the TM is in the Compare Match Output Mode, the pin
can be controlled by the TM to switch to a high or low level or to toggle when a compare match
situation occurs. The external TPn output pin is also the pin where the TM generates the PWM
output waveform. As the TM output pins are pin-shared with other function, the TM output function
must first be setup using registers. A single bit in one of the registers determines if its associated pin
is to be used as an external TM output pin or if it is to have another function.
TM Input/Output Pin Control Registers
Selecting to have a TM input/output or whether to retain its other shared functions is implemented
using one register with a single bit in each register corresponding to a TM input/output pin. Setting
the bit high will setup the corresponding pin as a TM input/output if reset to zero the pin will retain
its original other functions.
TMPC Register
Bit
7
6
5
4
3
2
1
0
Name
CLOP
—
—
—
—
—
T1CP
T0CP
R/W
R/W
—
—
—
—
—
R/W
R/W
POR
0
—
—
—
—
—
0
0
Bit 7 Rev. 1.00
CLOP: Control CLO function to CLO pin.
0: Normal I/O
1: CLO function
Bit 6 ~ 2
Unimplemented, read as "0"
Bit 1 T1CP: Control TP1 function to TP1 pin.
0: Normal I/O
1: TP1 function
Bit 0 T0CP: Control TP0 function to TP0 pin.
0: Normal I/O
1: TP0 function
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Programming Considerations
The TM Counter Registers, the Capture/Compare CCRA registers and CCRP registers, being 10-bit,
all have a low and high byte structure. The high bytes can be directly accessed, but as the low bytes
can only be accessed via an internal 8-bit buffer, reading or writing to these register pairs must be
carried out in a specific way. The important point to note is that data transfer to and from the 8-bit
buffer and its related low byte only takes place when a write or read operation to its corresponding
high byte is executed.
As the CCRA registers and CCRP registers are implemented in the way shown in the following
diagram and accessing these register pairs is carried out in a specific way described above, it is
recommended to use the "MOV" instruction to access the CCRA or CCRP low byte registers, named
TMxAL or TMxRPL, using the following access procedures. Accessing the CCRA or CCRP low
byte register without following these access procedures will result in unpredictable values.
     The following steps show the read and write procedures:
• Writing Data to CCRA or CCRP
♦♦ Step 1. Write data to Low Byte TMxAL or TMxRPL
– Note that here data is only written to the 8-bit buffer.
♦♦ Step 2. Write data to High Byte TMxAH or TMxRPH
– Here data is written directly to the high byte registers and simultaneously data is latched
from the 8-bit buffer to the Low Byte registers.
• Reading Data from the Counter Registers and CCRA or CCRP
♦♦ Step 1. Read data from the High Byte TMxDH, TMxAH or TMxRPH
– Here data is read directly from the High Byte registers and simultaneously data is latched
from the Low Byte register into the 8-bit buffer.
♦♦ Step 2. Read data from the Low Byte TMxDL, TMxAL or TMxRPL
– This step reads data from the 8-bit buffer.
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Periodic Type TM – PTM
The Periodic Type TM contains five operating modes, which are Compare Match Output, Timer/
Event Counter, Capture Input, Single Pulse Output and PWM Output modes. The Periodic TM can
also be controlled with an external input pin and can drive one external output pin.
Periodic TM Operation
The size of the two P-type TMs is 10-bit wide. At the core is a 10 count-up counter which is driven
by a user selectable internal or external clock source. There are also two internal comparators with
the names, Comparator A and Comparator P. These comparators will compare the value in the
counter with CCRP and CCRA registers. The CCRP comparator is 10-bit wide.
The only way of changing the value of the 10-bit counter using the application program, is to
clear the counter by changing the TnON bit from low to high. The counter will also be cleared
automatically by a counter overflow or a compare match with one of its associated comparators.
When these conditions occur, a TM interrupt signal will also usually be generated. The P-type Type
TM can operate in a number of different operational modes, can be driven by different clock sources
including an input pin and can also control an output pin. All operating setup conditions are selected
using relevant internal registers.
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Periodic Type TM Block Diagram (n=0, 1)
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Periodic Type TM Register Description
Overall operation of the Periodic TM is controlled using a series of registers. A read only register
pair exists to store the internal counter 10-bit value, while two read/write register pairs exist to store
the internal 10-bit CCRA and CCRP value. The remaining two registers are control registers which
setup the different operating and control modes.
Bit
Register
Name
7
6
5
4
3
TMnC0
TnPAU
TnCK2
TnCK1
TnCK0
TnON
—
TMnC1
TnM1
TnM0
TnIO1
TnIO0
TnOC
TnPOL
2
1
0
—
—
TnCAPTS TnCCLR
TMnDL
D7
D6
D5
D4
D3
D2
D1
D0
TMnDH
—
—
—
—
—
—
D9
D8
TMnAL
D7
D6
D5
D4
D3
D2
D1
D0
TMnAH
—
—
—
—
—
—
D9
D8
TMnRPL
D7
D6
D5
D4
D3
D2
D1
D0
TMnRPH
—
—
—
—
—
—
D9
D8
10-bit Periodic TM Register List (n=0, 1)
TMnC0 Register
Bit
7
6
5
4
3
2
1
0
Name
TnPAU
TnCK2
TnCK1
TnCK0
TnON
—
—
—
R/W
R/W
R/W
R/W
R/W
R/W
—
—
—
POR
0
0
0
0
0
—
—
—
Bit 7
TnPAU: TMn Counter Pause Control
0: run
1: pause
The counter can be paused by setting this bit high. Clearing the bit to zero restores
normal counter operation. When in a Pause condition the TM will remain powered up
and continue to consume power. The counter will retain its residual value when this bit
changes from low to high and resume counting from this value when the bit changes
to a low value again.
Bit 6 ~ 4TnCK2 ~ TnCK0: Select TMn Counter clock
000: fSYS/4
001: fSYS
010: fH/16
011: fH/64
100: fTBC
101: fH
110: TCKn rising edge clock
111: TCKn falling edge clock
These three bits are used to select the clock source for the TM. The external pin clock
source can be chosen to be active on the rising or falling edge. The clock source fSYS is
the system clock, while fH and fTBC are other internal clocks, the details of which can
be found in the oscillator section.
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Bit 3TnON: TMn Counter On/Off Control
0: Off
1: On
This bit controls the overall on/off function of the TM. Setting the bit high enables the
counter to run, clearing the bit disables the TM. Clearing this bit to zero will stop the
counter from counting and turn off the TM which will reduce its power consumption.
When the bit changes state from low to high the internal counter value will be reset to
zero, however when the bit changes from high to low, the internal counter will retain
its residual value until the bit returns high again.
If the TM is in the Compare Match Output Mode then the TM output pin will be reset
to its initial condition, as specified by the TM Output control bit, when the bit changes
from low to high.
Bit 2 ~ 0
Unimplemented, read as "0"
TMnC1 Register
Bit
7
6
5
4
3
2
1
0
Name
TnM1
TnM0
TnIO1
TnIO0
TnOC
TnPOL
TnCAPTS
TnCCLR
R/W
R/W
R/W
R/W
R/W
R/W
R/W
R/W
R/W
POR
0
0
0
0
0
0
0
0
Bit 7 ~ 6TnM1~TnM0: Select TMn Operation Mode
00: Compare Match Output Mode
01: Capture Input Mode
10: PWM Mode or Single Pulse Output Mode
11: Timer/Counter Mode
These bits setup the required operating mode for the TM. To ensure reliable operation
the TM should be switched off before any changes are made to the TnM1 and TnM0
bits. In the Timer/Counter Mode, the TM output pin control must be disabled.
Bit 5 ~ 4TnIO1~TnIO0: Select TPn output function
Compare Match Output Mode
00: No change
01: Output low
10: Output high
11: Toggle output
PWM Mode/Single Pulse Output Mode
00: PWM Output inactive state
01: PWM Output active state
10: PWM output
11: Single pulse output
Capture Input Mode
00: Input capture at rising edge of TPn or TCKn
01: Input capture at falling edge of TPn or TCKn
10: Input capture at falling/rising edge of TPn or TCKn
11: Input capture disabled
Timer/counter Mode
Unused
These two bits are used to determine how the TM output pin changes state when a
certain condition is reached. The function that these bits select depends upon in which
mode the TM is running.
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In the Compare Match Output Mode, the TnIO1 and TnIO0 bits determine how the
TM output pin changes state when a compare match occurs from the Comparator A.
The TM output pin can be setup to switch high, switch low or to toggle its present state
when a compare match occurs from the Comparator A. When these bits are both zero,
then no change will take place on the output. The initial value of the TM output pin
should be setup using the TnOC bit. Note that the output level requested by the TnIO1
and TnIO0 bits must be different from the initial value setup using the TnOC bit
otherwise no change will occur on the TM output pin when a compare match occurs.
After the TM output pin changes state it can be reset to its initial level by changing the
level of the TnON bit from low to high.
In the PWM Mode, the TnIO1 and TnIO0 bits determine how the TM output pin
changes state when a certain compare match condition occurs. The PWM output
function is modified by changing these two bits. It is necessary to change the values
of the TnIO1 and TnIO0 bits only after the TM has been switched off. Unpredictable
PWM outputs will occur if the TnIO1 and TnIO0 bits are changed when the TM is
running.
Bit 3TnOC: TPn Output control bit
Compare Match Output Mode
0: initial low
1: initial high
PWM Mode/ Single Pulse Output Mode
0: Active low
1: Active high
This is the output control bit for the TM output pin. Its operation depends upon
whether TM is being used in the Compare Match Output Mode or in the PWM Mode/
Single Pulse Output Mode. It has no effect if the TM is in the Timer/Counter Mode. In
the Compare Match Output Mode it determines the logic level of the TM output pin
before a compare match occurs. In the PWM Mode it determines if the PWM signal is
active high or active low.
Bit 2TnPOL: TPn Output polarity Control
0: non-invert
1: invert
This bit controls the polarity of the TPn output pin. When the bit is set high the TM
output pin will be inverted and not inverted when the bit is zero. It has no effect if the
TM is in the Timer/Counter Mode.
Bit 1TnCAPTS: TMn capture trigger source select
0: From TPn pin
1: From TCKn pin
Bit 0TnCCLR: Select TMn Counter clear condition
0: TMn Comparator P match
1: TMn Comparator A match
This bit is used to select the method which clears the counter. Remember that the
Periodic TM contains two comparators, Comparator A and Comparator P, either of
which can be selected to clear the internal counter. With the TnCCLR bit set high,
the counter will be cleared when a compare match occurs from the Comparator A.
When the bit is low, the counter will be cleared when a compare match occurs from
the Comparator P or with a counter overflow. A counter overflow clearing method can
only be implemented if the CCRP bits are all cleared to zero. The TnCCLR bit is not
used in the PWM, Single Pulse or Input Capture Mode.
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TMnDL Register
Bit
7
6
5
4
3
2
1
0
Name
D7
D6
D5
D4
D3
D2
D1
D0
R/W
R
R
R
R
R
R
R
R
POR
0
0
0
0
0
0
0
0
Bit 7 ~ 0TMnDL: TMn Counter Low Byte Register bit 7 ~ bit 0
TMn 10-bit Counter bit 7 ~ bit 0
TMnDH Register
Bit
7
6
5
4
3
2
1
0
Name
—
—
—
—
—
—
D9
D8
R/W
—
—
—
—
—
—
R
R
POR
—
—
—
—
—
—
0
0
Bit 7 ~ 2
Unimplemented, read as "0"
Bit 1 ~ 0
TMnDH: TMn Counter High Byte Register bit 1 ~ bit 0
TMn 10-bit Counter bit 9 ~ bit 8
TMnAL Register
Bit
7
6
5
4
3
2
1
0
Name
D7
D6
D5
D4
D3
D2
D1
D0
R/W
R/W
R/W
R/W
R/W
R/W
R/W
R/W
R/W
POR
0
0
0
0
0
0
0
0
1
0
Bit 7 ~ 0TMnAL: TMn CCRA Low Byte Register bit 7 ~ bit 0
TMn 10-bit CCRA bit 7 ~ bit 0
TMnAH Register
Bit
7
6
5
4
3
2
Name
—
—
—
—
—
—
D9
D8
R/W
—
—
—
—
—
—
R/W
R/W
POR
—
—
—
—
—
—
0
0
2
1
0
Bit 7 ~ 2
Unimplemented, read as "0"
Bit 1 ~ 0
TMnAH: TMn CCRA High Byte Register bit 1 ~ bit 0
TMn 10-bit CCRA bit 9 ~ bit 8
TMnRPL Register
Bit
7
6
5
4
3
Name
D7
D6
D5
D4
D3
D2
D1
D0
R/W
R/W
R/W
R/W
R/W
R/W
R/W
R/W
R/W
POR
0
0
0
0
0
0
0
0
Bit 7 ~ 0TMnRPL: TMn CCRP Low Byte Register bit 7 ~ bit 0
TMn 10-bit CCRP bit 7 ~ bit 0
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TMnRPH Register
Bit
7
6
5
4
3
2
1
0
Name
—
—
—
—
—
—
D9
D8
R/W
—
—
—
—
—
—
R/W
R/W
POR
—
—
—
—
—
—
0
0
Bit 7 ~ 2
Unimplemented, read as "0"
Bit 1 ~ 0
TMnRPH: TMn CCRP High Byte Register bit 1 ~ bit 0
TMn 10-bit CCRP bit 9 ~ bit 8
Periodic Type TM Operating Modes
The Periodic Type TM can operate in one of five operating modes, Compare Match Output Mode,
PWM Output Mode, Single Pulse Output Mode, Capture Input Mode or Timer/Counter Mode. The
operating mode is selected using the TnM1 and TnM0 bits in the TMnC1 register.
Compare Match Output Mode
To select this mode, bits TnM1 and TnM0 in the TMnC1 register, should be all cleared to 00
respectively. In this mode once the counter is enabled and running it can be cleared by three
methods. These are a counter overflow, a compare match from Comparator A and a compare match
from Comparator P. When the TnCCLR bit is low, there are two ways in which the counter can be
cleared. One is when a compare match occurs from Comparator P, the other is when the CCRP bits
are all zero which allows the counter to overflow. Here both the TnAF and TnPF interrupt request
flags for Comparator A and Comparator P respectively, will both be generated.
If the TnCCLR bit in the TMnC1 register is high then the counter will be cleared when a compare
match occurs from Comparator A. However, here only the TnAF interrupt request flag will be
generated even if the value of the CCRP bits is less than that of the CCRA registers. Therefore when
TnCCLR is high no TnPF interrupt request flag will be generated. In the Compare Match Output
Mode, the CCRA can not be set to "0".
As the name of the mode suggests, after a comparison is made, the TM output pin, will change
state. The TM output pin condition however only changes state when a TnAF interrupt request flag
is generated after a compare match occurs from Comparator A. The TnPF interrupt request flag,
generated from a compare match from Comparator P, will have no effect on the TM output pin. The
way in which the TM output pin changes state are determined by the condition of the TnIO1 and
TnIO0 bits in the TMnC1 register. The TM output pin can be selected using the TnIO1 and TnIO0
bits to go high, to go low or to toggle from its present condition when a compare match occurs from
Comparator A. The initial condition of the TM output pin, which is setup after the TnON bit changes
from low to high, is setup using the TnOC bit. Note that if the TnIO1, TnIO0 bits are zero then no
pin change will take place.
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Co�nter Va��e
Co�nter overf�ow
CCRP=0
0x�FF
TnCCLR = 0; TnM [1:0] = 00
CCRP > 0
Co�nter c�eared b� CCRP va��e
CCRP > 0
Co�nter
Restart
Res�me
CCRP
Pa�se
CCRA
Stop
Time
TnON
TnPAU
TnPOL
CCRP Int.
F�ag TnPF
CCRA Int.
F�ag TnAF
TM O/P Pin
O�tp�t pin set to
initia� Leve� Low
if TnOC=0
O�tp�t not affected b� TnAF
f�ag. Remains High �nti� reset
b� TnON bit
O�tp�t Togg�e with
TnAF f�ag
Here TnIO [1:0] = 11
Togg�e O�tp�t se�ect
Note TnIO [1:0] = 10
Active High O�tp�t se�ect
O�tp�t Inverts
when TnPOL is high
O�tp�t Pin
Reset to Initia� va��e
O�tp�t contro��ed b�
other pin-shared f�nction
Compare Match Output Mode – TnCCLR = 0
Note: 1. With TnCCLR = 0 – a Comparator P match will clear the counter
2. The TM output pin is controlled only by the TnAF flag
3. The output pin is reset to initial state by a TnON bit rising edge
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Co�nter Va��e
TnCCLR = 1; TnM [1:0] = 00
CCRA = 0
Co�nter overf�ow
CCRA > 0 Co�nter c�eared b� CCRA va��e
0x�FF
CCRA=0
Res�me
CCRA
Pa�se
Stop
Co�nter Restart
CCRP
Time
TnON
TnPAU
TnPOL
No TnAF f�ag
generated on
CCRA overf�ow
CCRA Int.
F�ag TnAF
CCRP Int.
F�ag TnPF
TnPF not
generated
O�tp�t does
not change
TM O/P Pin
O�tp�t pin set to
initia� Leve� Low
if TnOC=0
O�tp�t not affected b�
TnAF f�ag. Remains High
�nti� reset b� TnON bit
O�tp�t Togg�e with
TnAF f�ag
Here TnIO [1:0] = 11
Togg�e O�tp�t se�ect
Note TnIO [1:0] = 10
Active High O�tp�t se�ect
O�tp�t Inverts
when TnPOL is high
O�tp�t Pin
Reset to Initia� va��e
O�tp�t contro��ed b�
other pin-shared f�nction
Compare Match Output Mode – TnCCLR = 1
Note: 1. With TnCCLR = 1 – a Comparator A match will clear the counter
2. The TM output pin is controlled only by the TnAF flag
3. The output pin is reset to initial state by a TnON rising edge
4. The TnPF flag is not generated when TnCCLR = 1
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Timer/Counter Mode
To select this mode, bits TnM1 and TnM0 in the TMnC1 register should all be set to 11 respectively.
The Timer/Counter Mode operates in an identical way to the Compare Match Output Mode
generating the same interrupt flags. The exception is that in the Timer/Counter Mode the TM output
pin is not used. Therefore the above description and Timing Diagrams for the Compare Match
Output Mode can be used to understand its function. As the TM output pin is not used in this mode,
the pin can be used as a normal I/O pin or other pin-shared function.
PWM Output Mode
To select this mode, bits TnM1 and TnM0 in the TMnC1 register should be set to 10 respectively
and also the TnIO1 and TnIO0 bits should be set to 10 respectively. The PWM function within
the TM is useful for applications which require functions such as motor control, heating control,
illumination control etc. By providing a signal of fixed frequency but of varying duty cycle on the
TM output pin, a square wave AC waveform can be generated with varying equivalent DC RMS
values.
As both the period and duty cycle of the PWM waveform can be controlled, the choice of generated
waveform is extremely flexible. In the PWM mode, the TnCCLR bit has no effect as the PWM
period. Both of the CCRP and CCRA registers are used to generate the PWM waveform, one register
is used to clear the internal counter and thus control the PWM waveform frequency, while the other
one is used to control the duty cycle. The PWM waveform frequency and duty cycle can therefore
be controlled by the values in the CCRA and CCRP registers.
An interrupt flag, one for each of the CCRA and CCRP, will be generated when a compare match
occurs from either Comparator A or Comparator P. The TnOC bit in the TMnC1 register is used to
select the required polarity of the PWM waveform while the two TnIO1 and TnIO0 bits are used to
enable the PWM output or to force the TM output pin to a fixed high or low level. The TnPOL bit is
used to reverse the polarity of the PWM output waveform.
10-bit PTM, PWM Mode, Edge-aligned Mode
CCRP
1~1023
Period
1~1023
Duty
0000B
1024
CCRA
If fSYS = 16MHz, TM clock source select fSYS/4, CCRP = 512 and CCRA = 128,
The PTM PWM output frequency = (fSYS/4) / (2×256) = fSYS/2048 = 7.8125kHz, duty = 128/512 =
25%,
If the Duty value defined by the CCRA register is equal to or greater than the Period value, then the
PWM output duty is 100%.
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Co�nter Va��e
TnDPX = 0; TnM [1:0] = 10
Co�nter c�eared
b� CCRP
Co�nter Reset when
TnON ret�rns high
CCRP
Pa�se Res�me
CCRA
Co�nter Stop if
TnON bit �ow
Time
TnON
TnPAU
TnPOL
CCRA Int.
F�ag TnAF
CCRP Int.
F�ag TnPF
TM O/P Pin
(TnOC=1)
TM O/P Pin
(TnOC=0)
PWM D�t� C�c�e
set b� CCRA
PWM Period
set b� CCRP
PWM res�mes
operation
O�tp�t contro��ed b�
O�tp�t Inverts
other pin-shared f�nction
when TnPOL = 1
PWM Mode
Note: 1. Here Counter cleared by CCRP
2. A counter clear sets the PWM Period
3. The internal PWM function continues running even when TnIO[1:0] = 00 or 01
4. The TnCCLR bit has no influence on PWM operation
Single Pulse Mode
To select this mode, the required bit pairs, TnM1 and TnM0 should be set to 10 respectively and also
the corresponding TnIO1 and TnIO0 bits should be set to 11 respectively. The Single Pulse Output
Mode, as the name suggests, will generate a single shot pulse on the TM output pin.
The trigger for the pulse output leading edge is a low to high transition of the TnON bit, which can
be implemented using the application program. However in the Single Pulse Mode, the TnON bit
can also be made to automatically change from low to high using the external TCKn pin, which will
in turn initiate the Single Pulse output. When the TnON bit transitions to a high level, the counter
will start running and the pulse leading edge will be generated. The TnON bit should remain high
when the pulse is in its active state. The generated pulse trailing edge will be generated when the
TnON bit is cleared to zero, which can be implemented using the application program or when a
compare match occurs from Comparator A.
However a compare match from Comparator A will also automatically clear the TnON bit and thus
generate the Single Pulse output trailing edge. In this way the CCRA value can be used to control the
pulse width. A compare match from Comparator A will also generate TM interrupts. The counter can
only be reset back to zero when the TnON bit changes from low to high when the counter restarts. In
the Single Pulse Mode CCRP is not used. The TnCCLR bit is also not used.
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            Single Pulse Generation
Co�nter Va��e
TnM [1:0] = 10 ; TnIO [1:0] = 11
Co�nter stopped
b� CCRA
Co�nter Reset when
TnON ret�rns high
CCRA
Pa�se
Co�nter Stops
b� software
Res�me
CCRP
Time
TnON
Software
Trigger
A�to. set b�
TCKn pin
C�eared b�
CCRA match
TCKn pin
Software
Trigger
Software
Trigger
Software
C�ear
Software
Trigger
TCKn pin
Trigger
TnPAU
TnPOL
CCRP Int.
F�ag TnPF
No CCRP Interr�pts
generated
CCRA Int.
F�ag TnAF
TM O/P Pin
(TnOC=1)
TM O/P Pin
(TnOC=0)
O�tp�t Inverts
when TnPOL = 1
P��se Width
set b� CCRA
Single Pulse Mode
Note: 1. Counter stopped by CCRA
2. CCRP is not used
3. The pulse is triggered by the TCKn pin or by setting the TnON bit high
4. A TCKn pin active edge will automatically set the TnON bit high
5. In the Single Pulse Mode, TnIO [1:0] must be set to "11" and can not be changed.
Capture Input Mode
To select this mode bits TnM1 and TnM0 in the TMnC1 register should be set to 01 respectively.
This mode enables external signals to capture and store the present value of the internal counter
and can therefore be used for applications such as pulse width measurements. The external signal is
supplied on the TPn or TCKn pin, selected by the TnCAPTS bit in the TMnC0 register. The input
pin active edge can be either a rising edge, a falling edge or both rising and falling edges; the active
edge transition type is selected using the TnIO1 and TnIO0 bits in the TMnC1 register. The counter is
started when the TnON bit changes from low to high which is initiated using the application program.
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When the required edge transition appears on the TPn or TCKn pin the present value in the counter
will be latched into the CCRA register and a TM interrupt generated. Irrespective of what events
occur on the TPn or TCKn pin the counter will continue to free run until the TnON bit changes from
high to low. When a CCRP compare match occurs the counter will reset back to zero; in this way
the CCRP value can be used to control the maximum counter value. When a CCRP compare match
occurs from Comparator P, a TM interrupt will also be generated. Counting the number of overflow
interrupt signals from the CCRP can be a useful method in measuring long pulse widths. The TnIO1
and TnIO0 bits can select the active trigger edge on the TPn or TCKn pin to be a rising edge, falling
edge or both edge types. If the TnIO1 and TnIO0 bits are both set high, then no capture operation
will take place irrespective of what happens on the TPn or TCKn pin, however it must be noted that
the counter will continue to run.
As the TPn or TCKn pin is pin shared with other functions, care must be taken if the TMn is in the
Capture Input Mode. This is because if the pin is setup as an output, then any transitions on this pin
may cause an input capture operation to be executed. The TnCCLR, TnOC and TnPOL bits are not
used in this Mode.
Co�nter Va��e
TnM [1:0] = 01
Co�nter c�eared
b� CCRP
Co�nter Co�nter
Stop
Reset
CCRP
YY
Pa�se
Res�me
XX
Time
TnON
TnPAU
TM capt�re pin
TPn or TCKn
Active
edge
Active
edge
Active edge
CCRA Int.
F�ag TnAF
CCRP Int.
F�ag TnPF
CCRA
Va��e
TnIO [1:0]
Va��e
XX
00 – Rising edge
YY
01 – Fa��ing edge
XX
10 – Both edges
YY
11 – Disab�e Capt�re
Capture Input Mode
Note: 1. TnM [1:0] = 01 and active edge set by the TnIO[1:0] bits
2. A TM Capture input pin active edge transfers counter value to CCRA
3. The TnCCLR bit is not used
4. No output function – TnOC and TnPOL bits are not used
5. CCRP determines the counter value and the counter has a maximum count value when
CCRP is equal to zero
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Analog to Digital Converter
The need to interface to real world analog signals is a common requirement for many electronic
systems. However, to properly process these signals by a microcontroller, they must first be
converted into digital signals by A/D converters. By integrating the A/D conversion electronic
circuitry into the microcontroller, the need for external components is reduced significantly with the
corresponding follow-on benefits of lower costs and reduced component space requirements.
A/D Overview
This device contains a multi-channel analog to digital converter which can directly interface to
external analog signals, such as that from sensors or other control signals and convert these signals
directly into either a 12-bit digital value.
Input Channels
A/D Channel Select Bits
Input Pins
8
ACS4, ACS2~ACS0
AN0~AN7
The accompanying block diagram shows the overall internal structure of the A/D converter, together
with its associated registers.
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 A/D Converter Structure
A/D Converter Register Description
Overall operation of the A/D converter is controlled using five registers. A read only register pair
ADRL/ADRH exists to store the ADC data 12-bit value. The remaining three registers are control
registers which setup the operating and control function of the A/D converter.
Register Name
Bit
7
6
5
4
3
2
1
0
ADRL(ADRFS=0)
D3
D2
D1
D0
—
—
—
—
ADRL(ADRFS=1)
D7
D6
D5
D4
D3
D2
D1
D0
ADRH(ADRFS=0)
D11
D10
D9
D8
D7
D6
D5
D4
ADRH(ADRFS=1)
—
—
—
—
D11
D10
D9
D8
ADCR0
START
EOCB
ADOFF
ADRFS
—
ACS2
ACS1
ACS0
ADCR1
ACS4
V125EN
—
VREFS
—
ADCK2
ADCK1
ADCK0
ACERL
ACE7
ACE6
ACE5
ACE4
ACE3
ACE2
ACE1
ACE0
A/D Converter Register List
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A/D Converter Data Registers – ADRL, ADRH
As this device contains an internal 12-bit A/D converter, it requires two data registers to store the
converted value. These are a high byte register, known as ADRH, and a low byte register, known
as ADRL. After the conversion process takes place, these registers can be directly read by the
microcontroller to obtain the digitised conversion value. As only 12 bits of the 16-bit register space
is utilised, the format in which the data is stored is controlled by the ADRFS bit in the ADCR0
register as shown in the accompanying table. D0~D11 are the A/D conversion result data bits. Any
unused bits will be read as zero.
ADRFS
0
1
ADRH
7
6
D11 D10
0
0
ADRL
5
4
3
2
1
0
7
6
5
4
3
2
1
0
D9
D8
D7
D6
D5
D4
D3
D2
D1
D0
0
0
0
0
0
0
D11 D10
D9
D8
D7
D6
D5
D4
D3
D2
D1
D0
A/D Data Registers
A/D Converter Control Registers – ADCR0, ADCR1, ACERL
To control the function and operation of the A/D converter, three control registers known as ADCR0,
ADCR1 and ACERL are provided. These 8-bit registers define functions such as the selection of
which analog channel is connected to the internal A/D converter, the digitised data format, the A/
D clock source as well as controlling the start function and monitoring the A/D converter end of
conversion status. The ACS2~ACS0 bits in the ADCR0 register define the ADC input channel
number. As the device contains only one actual analog to digital converter hardware circuit, each
of the individual 8 analog inputs must be routed to the converter. It is the function of the ACS4 and
ACS2~ACS0 bits to determine which analog channel input pins or 1.25V is actually connected to
the internal A/D converter.
The ACERL control register contains the ACE7~ACE0 bits which determine which pins are used
as analog inputs for the A/D converter input and which pins are not to be used as the A/D converter
input. Setting the corresponding bit high will select the A/D input function, clearing the bit to zero
will select either the I/O or other pin-shared function. When the pin is selected to be an A/D input,
its original function whether it is an I/O or other pin-shared function will be removed. In addition,
any internal pull-high resistors connected to these pins will be automatically removed if the pin is
selected to be an A/D input.
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ADCR0 Register
Bit
7
6
5
4
3
2
1
0
Name
START
EOCB
ADOFF
ADRFS
—
ACS2
ACS1
ACS0
R/W
R/W
R
R/W
R/W
—
R/W
R/W
R/W
POR
0
1
1
0
—
0
0
0
Bit 7
START: Start the A/D conversion
0→1→0: Start
0→1: Reset the A/D converter and set EOCB to "1"This bit is used to initiate an
A/D conversion process. The bit is normally low but if set high and then cleared
low again, the A/D converter will initiate a conversion process. When the bit is set
high the A/D converter will be reset.
Bit 6EOCB: End of A/D conversion flag
0: A/D conversion ended
1: A/D conversion in progress
This read only flag is used to indicate when an A/D conversion process has completed.
When the conversion process is running the bit will be high.
Bit 5
ADOFF : ADC module power on/off control bit
0: ADC module power on
1: ADC module power off
This bit controls the power to the A/D internal function. This bit should be cleared
to zero to enable the A/D converter. If the bit is set high then the A/D converter will
be switched off reducing the device power consumption. As the A/D converter will
consume a limited amount of power, even when not executing a conversion, this may
be an important consideration in power sensitive battery powered applications.
Note: 1. it is recommended to set ADOFF=1 before entering IDLE/SLEEP Mode for
saving power.
2. ADOFF=1 will power down the ADC module.
Bit 4ADRFS: ADC Data Format Control
0: A/D Data MSB is ADRH bit 7, LSB is ADRL bit 4
1: A/D Data MSB is ADRH bit 3, LSB is ADRL bit 0
This bit controls the format of the 12-bit converted A/D value in the two A/D data
registers. Details are provided in the A/D data register section.
Rev. 1.00
Bit 3
Unimplemented, read as "0"
Bit 2 ~ 0
ACS2 ~ ACS0: Select A/D channel (when ACS4 is "0")
000: AN0
001: AN1
010: AN2
011: AN3
100: AN4
101: AN5
110: AN6
111: AN7
These are the A/D channel select control bits. As there is only one internal hardware
A/D converter each of the eight A/D inputs must be routed to the internal converter
using these bits. If bit ACS4 in the ADCR1 register is set high then the internal 1.25V
will be routed to the A/D Converter.
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ADCR1 Register
Rev. 1.00
Bit
7
6
5
4
3
2
1
0
Name
ACS4
V125EN
—
VREFS
—
ADCK2
ADCK1
ADCK0
R/W
R/W
R/W
—
R/W
—
R/W
R/W
R/W
POR
0
0
—
0
—
0
0
0
Bit 7
ACS4: Select Internal 1.25V as ADC input Control
0: Disable
1: Enable
This bit enables 1.25V to be connected to the A/D converter. The V125EN bit must
first have been set to enable the bandgap circuit 1.25V voltage to be used by the A/D
converter. When the ACS4 bit is set high, the bandgap 1.25V voltage will be routed to
the A/D converter and the other A/D input channels disconnected.
Bit 6
V125EN: Internal 1.25V Control
0: Disable
1: Enable
This bit controls the internal Bandgap circuit on/off function to the A/D converter.
When the bit is set high the bandgap voltage 1.25V can be used by the A/D converter.
If 1.25V is not used by the A/D converter and the LVR/LVD function is disabled then
the bandgap reference circuit will be automatically switched off to conserve power.
When 1.25V is switched on for use by the A/D converter, a time tBG should be allowed
for the bandgap circuit to stabilise before implementing an A/D conversion.
Bit 5
Unimplemented, read as "0"
Bit 4
VREFS: Select ADC reference voltage
0: internal ADC power
1: VREF pin
This bit is used to select the reference voltage for the A/D converter. If the bit is high,
then the A/D converter reference voltage is supplied on the external VREF pin. If the
pin is low, then the internal reference is used which is taken from the power supply pin
VDD. When the A/D converter reference voltage is supplied on the external VREF pin
which is pin-shared with other functions, all of the pin-shared functions except VREF
on this pin are disabled.
Bit3
Unimplemented, read as "0"
Bit 2 ~ 0
ADCK2 ~ ADCK0: Select ADC clock source
000: fSYS
001: fSYS/2
010: fSYS/4
011: fSYS/8
100: fSYS/16
101: fSYS/32
110: fSYS/64
111: Undefined
These three bits are used to select the clock source for the A/D converter.
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ACERL Register
Bit
7
6
5
4
3
2
1
0
Name
ACE7
ACE6
ACE5
ACE4
ACE3
ACE2
ACE1
ACE0
R/W
R/W
R/W
R/W
R/W
R/W
R/W
R/W
R/W
POR
1
1
1
1
1
1
1
1
Bit 7ACE7: Define PB3 is A/D input or not
0: not A/D input
1: A/D input, AN7
Bit 6ACE6: Define PA7 is A/D input or not
0: not A/D input
1: A/D input, AN6
Bit 5ACE5: Define PA6 is A/D input or not
0: not A/D input
1: A/D input, AN5
Bit 4ACE4: Define PA5 is A/D input or not
0: not A/D input
1: A/D input, AN4
Bit 3ACE3: Define PA4 is A/D input or not
0: not A/D input
1: A/D input, AN3
Bit 2ACE2: Define PB2 is A/D input or not
0: not A/D input
1: A/D input, AN2
Bit 1ACE1: Define PB1 is A/D input or not
0: not A/D input
1: A/D input, AN1
Bit 0ACE0: Define PB0 is A/D input or not
0: not A/D input
1: A/D input, AN0
A/D Operation
The START bit in the ADCR0 register is used to start and reset the A/D converter. When the
microcontroller sets this bit from low to high and then low again, an analog to digital conversion cycle
will be initiated. When the START bit is brought from low to high but not low again, the EOCB bit in
the ADCR0 register will be set high and the analog to digital converter will be reset. It is the START
bit that is used to control the overall start operation of the internal analog to digital converter.
The EOCB bit in the ADCR0 register is used to indicate when the analog to digital conversion process
is complete. This bit will be automatically set to "0" by the microcontroller after a conversion cycle
has ended. In addition, the corresponding A/D interrupt request flag will be set in the interrupt control
register, and if the interrupts are enabled, an appropriate internal interrupt signal will be generated.
This A/D internal interrupt signal will direct the program flow to the associated A/D internal
interrupt address for processing. If the A/D internal interrupt is disabled, the microcontroller can
be used to poll the EOCB bit in the ADCR0 register to check whether it has been cleared as an
alternative method of detecting the end of an A/D conversion cycle.
The clock source for the A/D converter, which originates from the system clock fSYS, can be chosen
to be either fSYS or a subdivided version of fSYS. The division ratio value is determined by the
ADCK2~ADCK0 bits in the ADCR1 register. Although the A/D clock source is determined by the
system clock, fSYS, and by bits ADCK2~ADCK0, there are some limitations on the maximum A/
D clock source speed that can be selected. As the recommended range of permissible A/D clock
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period, tADCK, is from 0.5μs to 10μs, care must be taken for selected system clock frequencies.
For example, if the system clock operates at a frequency of 4MHz, the ADCK2~ADCK0 bits should
not be set to 000B or 110B. Doing so will give A/D clock periods that are less than the minimum A/
D clock period or greater than the maximum A/D clock period which may result in inaccurate A/D
conversion values.
Refer to the following table for examples, where values marked with an asterisk * show where,
depending upon the device, special care must be taken, as the values may be less than the specified
minimum A/D Clock Period.
A/D clock Period (tADCK)
fSYS
1MHz
ADCK2,
ADCK1,
ADCK0
=000
(fSYS)
ADCK2,
ADCK1,
ADCK0
=001
(fSYS/2)
ADCK2,
ADCK1,
ADCK0
=010
(fSYS/4)
ADCK2,
ADCK1,
ADCK0
=011
(fSYS/8)
ADCK2,
ADCK1,
ADCK0
=100
(fSYS/16)
ADCK2,
ADCK1,
ADCK0
=101
(fSYS/32)
ADCK2,
ADCK1,
ADCK0
=110
(fSYS/64)
ADCK2,
ADCK1,
ADCK0
=111
1μs
2μs
4μs
8μs
16μs*
32μs*
64μs*
Undefined
2MHz
500ns
1μs
2μs
4μs
8μs
16μs*
32μs*
Undefined
4MHz
250ns*
500ns
1μs
2μs
4μs
8μs
16μs*
Undefined
8MHz
125ns*
250ns*
500ns
1μs
2μs
4μs
8μs
Undefined
12MHz
83ns*
167ns*
333ns*
667ns*
1.33μs
2.67μs
5.33μs
Undefined
A/D Clock Period Examples
Controlling the power on/off function of the A/D converter circuitry is implemented using the
ADOFF bit in the ADCR0 register. This bit must be zero to power on the A/D converter. When the
ADOFF bit is cleared to zero to power on the A/D converter internal circuitry a certain delay, as
indicated in the timing diagram, must be allowed before an A/D conversion is initiated. Even if no
pins are selected for use as A/D inputs by clearing the ACE7~ACE0 bits in the ACERL registers, if
the ADOFF bit is zero then some power will still be consumed. In power conscious applications it
is therefore recommended that the ADOFF is set high to reduce power consumption when the A/D
converter function is not being used.
The reference voltage supply to the A/D Converter can be supplied from either the positive power
supply pin, AVDD, or from an external reference sources supplied on pin VREF. The desired
selection is made using the VREFS bit. As the VREF pin is pin-shared with other functions, when
the VREFS bit is set high, the VREF pin function will be selected and the other pin functions will be
disabled automatically.
A/D Input Pins
All of the A/D analog input pins are pin-shared with the I/O pins on Port A as well as other
functions. The ACE7~ ACE0 bits in the ACERL registers, determine whether the input pins are setup
as A/D converter analog inputs or whether they have other functions. If the ACE7~ ACE0 bits for its
corresponding pin is set high then the pin will be setup to be an A/D converter input and the original
pin functions disabled. In this way, pins can be changed under program control to change their
function between A/D inputs and other functions. All pull-high resistors, which are setup through
register programming, will be automatically disconnected if the pins are setup as A/D inputs. Note
that it is not necessary to first setup the A/D pin as an input in the PAC or PBC port control registers
to enable the A/D input as when the ACE7~ ACE0 bits enable an A/D input, the status of the port
control register will be overridden.
The A/D converter has its own reference voltage pin, VREF, however the reference voltage can
also be supplied from the power supply pin, a choice which is made through the VREFS bit in the
ADCR1 register. The analog input values must not be allowed to exceed the value of VREF.
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 ­     
   A/D Input Structure
Summary of A/D Conversion Steps
The following summarises the individual steps that should be executed in order to implement an A/
D conversion process.
• Step 1
Select the required A/D conversion clock by correctly programming bits ADCK2~ADCK0 in the
ADCR1 register.
• Step 2
Enable the A/D by clearing the ADOFF bit in the ADCR0 register to zero.
• Step 3
Select which channel is to be connected to the internal A/D converter by correctly programming
the ACS4, ACS2~ACS0 bits which are also contained in the ADCR1 and ADCR0 registers.
• Step 4
Select which pins are to be used as A/D inputs and configure them by correctly programming the
ACE7~ACE0 bits in the ACERL register.
• Step 5
If the interrupts are to be used, the interrupt control registers must be correctly configured to
ensure the A/D converter interrupt function is active. The master interrupt control bit, EMI, and
the A/D converter interrupt bit, ADE, must both be set high to do this.
• Step 6
The analog to digital conversion process can now be initialised by setting the START bit in
the ADCR0 register from low to high and then low again. Note that this bit should have been
originally cleared to zero.
• Step 7
To check when the analog to digital conversion process is complete, the EOCB bit in the ADCR0
register can be polled. The conversion process is complete when this bit goes low. When this
occurs the A/D data register ADRL and ADRH can be read to obtain the conversion value. As an
alternative method, if the interrupts are enabled and the stack is not full, the program can wait for
an A/D interrupt to occur.
Note: When checking for the end of the conversion process, if the method of polling the EOCB bit
in the ADCR0 register is used, the interrupt enable step above can be omitted.
The accompanying diagram shows graphically the various stages involved in an analog to digital
conversion process and its associated timing. After an A/D conversion process has been initiated
by the application program, the microcontroller internal hardware will begin to carry out the
conversion, during which time the program can continue with other functions. The time taken for the
A/D conversion is 16tADCK where tADCK is equal to the A/D clock period.
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Programming Considerations
During microcontroller operations where the A/D converter is not being used, the A/D internal
circuitry can be switched off to reduce power consumption, by setting bit ADOFF high in the
ADCR0 register. When this happens, the internal A/D converter circuits will not consume power
irrespective of what analog voltage is applied to their input lines. If the A/D converter input lines are
used as normal I/Os, then care must be taken as if the input voltage is not at a valid logic level, then
this may lead to some increase in power consumption.
A/D Transfer Function
As the device contains a 12-bit A/D converter, its full-scale converted digitised value is equal to
FFFH. Since the full-scale analog input value is equal to the VDD voltage, this gives a single bit
analog input value of AVDD or VREF divided by 4096.
1 LSB= (VDD or VREF) / 4096
The A/D Converter input voltage value can be calculated using the following equation:
A/D input voltage = A/D output digital value ×(VDD or VREF) / 4096
The diagram shows the ideal transfer function between the analog input value and the digitised
output value for the A/D converter. Except for the digitised zero value, the subsequent digitised
values will change at a point 0.5 LSB below where they would change without the offset, and the
last full scale digitised value will change at a point 1.5 LSB below the AVDD or VREF level.
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A/D Programming Examples
The following two programming examples illustrate how to setup and implement an A/D conversion.
In the first example, the method of polling the EOCB bit in the ADCR0 register is used to detect
when the conversion cycle is complete, whereas in the second example, the A/D interrupt is used to
determine when the conversion is complete.
Example: using an EOCB polling method to detect the end of conversion
clr
ADE; disable ADC interrupt
mov a, 03H
mov ADCR1, a ; select fSYS/8 as A/D clock and switch off 1.25V
clr ADOFF
mova, FFh ; setup ACERL to configure pins AN0~AN7
mov ACERL, a
mov a, 00h
mov ADCR0, a ; enable and connect AN0 channel to A/D converter
:
:
Start_conversion:
clr START
set START ; reset A/D
clr START ; start A/D
Polling_EOC:
sz EOCB ; poll the ADCR0 register EOCB bit to detect end
; of A/D conversion
jmp polling_EOC ; continue polling
mov a, ADRL ; read low byte conversion result value
mov adrl_buffer, a ; save result to user defined register
mov a, ADRH ; read high byte conversion result value
mov adrh_buffer, a ; save result to user defined register
:
jmp start_conversion ; start next A/D conversion
Note: To power off the ADC, it is necessary to set ADOFF as "1".
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Example: using the interrupt method to detect the end of conversion
clr
ADE; disable ADC interrupt
mov a, 03H
mov ADCR1, a ; select fSYS/8 as A/D clock and switch off 1.25V
clr ADOFF
mova, FFh ; setup ACERL to configure pins AN0~AN7
mov ACERL, a
mov a, 00h
mov ADCR0, a ; enable and connect AN0 channel to A/D converter
:
:
Start_conversion:
clr START
set START ; reset A/D
clr START ; start A/D
clr ADF ; clear ADC interrupt request flag
set
ADE; enable ADC interrupt
set EMI ; enable global interrupt
:
:
; ADC interrupt service routine
ADC_:
mov acc_stack, a ; save ACC to user defined memory
mov a, STATUS
mov status_stack, a ; save STATUS to user defined memory
:
:
mov a, ADRL ; read low byte conversion result value
mov adrl_buffer, a ; save result to user defined register
mov a, ADRH ; read high byte conversion result value
mov adrh_buffer, a ; save result to user defined register
:
:
EXIT_ISR:
mov a, status_stack
mov STATUS, a ; restore STATUS from user defined memory
mov a, acc_stack ; restore ACC from user defined memory
clr ADF ; clear ADC interrupt flag
reti
Note: To power off the ADC, it is necessary to set ADOFF as "1".
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Interrupts
Interrupts are an important part of any microcontroller system. When an external event or an
internal function such as a Timer Module or an A/D converter requires microcontroller attention,
their corresponding interrupt will enforce a temporary suspension of the main program allowing the
microcontroller to direct attention to their respective needs. The device contains several external
interrupt and internal interrupts functions. The external interrupt is generated by the action of
the external INT0 and INT1 pins, while the internal interrupts are generated by various internal
functions such as the TMs, Time Base, LVD, EEPROM and the A/D converter.
Interrupt Registers
Overall interrupt control, which basically means the setting of request flags when certain
microcontroller conditions occur and the setting of interrupt enable bits by the application program,
is controlled by a series of registers, located in the Special Purpose Data Memory, as shown in the
accompanying table. The number of registers depends upon the device chosen but fall into three
categories. The first is the INTC0~INTC2 registers which setup the primary interrupts, the second
is the MFI0~MFI2 registers which setup the Multi-function interrupts. Finally there is an INTEG
register to setup the external interrupt trigger edge type.
Each register contains a number of enable bits to enable or disable individual registers as well as
interrupt flags to indicate the presence of an interrupt request. The naming convention of these
follows a specific pattern. First is listed an abbreviated interrupt type, then the (optional) number of
that interrupt followed by either an "E" for enable/disable bit or "F" for request flag.
Function
Enable Bit
Request Flag
Notes
Global
EMI
—
—
INTn Pin
INTnE
INTnF
n=0 or 1
Multi-function
MFnE
MFnF
n=0~2
Time Base
TBnE
TBnF
n=0 or 1
A/D Converter
ADE
ADF
—
LVD
LVE
LVF
—
—
EEPROM write
PTM
DEE
DEF
TnAE
TnAF
TnPE
TnPF
n=0 or 1
Interrupt Register Bit Naming Conventions
Name
Bit7
Bit6
Bit5
Bit4
Bit3
Bit2
Bit1
Bit0
INTEG
INTC0
—
—
—
MF0F
—
—
INT1S1
INT1S0
INT0S1
INT0S0
—
INT0F
MF0E
—
INT0E
EMI
INTC1
TB0F
INTC2
—
ADF
MF2F
MF1F
TB0E
ADE
MF2E
MF1E
—
INT1F
TB1F
—
—
INT1E
TB1E
MFI0
MFI1
—
—
T0AF
T0PF
—
—
T0AE
T0PE
—
—
T1AF
T1PF
—
—
T1AE
T1PE
MFI2
—
—
DEF
LVF
—
—
DEE
LVE
Interrupt Register Contents – HT66F0174
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Name
Bit
7
6
5
4
3
2
1
0
—
—
—
—
INT1S1
INT1S0
INT0S1
INT0S0
INTC0
—
MF0F
—
INT0F
MF0E
—
INT0E
EMI
INTC1
TB0F
ADF
MF2F
MF1F
TB0E
ADE
MF2E
MF1E
INTC2
—
—
INT1F
TB1F
—
—
INT1E
TB1E
MFI0
—
—
T0AF
T0PF
—
—
T0AE
T0PE
MFI1
—
—
T1AF
T1PF
—
—
T1AE
T1PE
MFI2
—
—
—
LVF
—
—
—
LVE
INTEG
Interrupt Register Contents – HT66F0172
INTEG Register
Bit
7
6
5
4
3
2
1
0
Name
—
—
—
—
INT1S1
INT1S0
INT0S1
INT0S0
R/W
—
—
—
—
R/W
R/W
R/W
R/W
POR
—
—
—
—
0
0
0
0
0
bit 7~4
Unimplemented, read as "0"
bit 3~2INT1S1, INT1S0: interrupt edge control for INT1 pin
00 : disable
01 : rising edge
10 : falling edge
11 : dual edge
bit 1~0INT0S1, INT0S0: interrupt edge control for INT0 pin
00 : disable
01 : rising edge
10 : falling edge
11 : dual edge
INTC0 Register
Bit
7
6
5
4
3
2
1
Name
—
MF0F
—
INT0F
MF0E
—
INT0E
EMI
R/W
—
R/W
—
R/W
R/W
—
R/W
R/W
POR
—
0
—
0
0
—
0
0
Bit 7
Bit 6
Unimplemented, read as "0"
MF0F: Multi-function Interrupt 0 Request Flag
0: No request
1: Interrupt request
Bit 5
Unimplemented, read as "0"
Bit 4
INT0F: INT0 Interrupt Request Flag
0: No request
1: Interrupt request
Bit 3 MF0E: Multi-function Interrupt 0 Control
0: Disable
1: Enable
Bit