ETC ST72121J2

ST72E121
ST72T121
8-BIT MCU WITH 8 TO 16K OTP/EPROM,
384 TO 512 BYTES RAM, WDG, SCI, SPI AND 2 TIMERS
DATASHEET
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User Program Memory (OTP/EPROM):
8 to 16K bytes
Data RAM: 384 to 512 bytes including 256 bytes
of stack
Master Reset and Power-On Reset
Low Voltage Detector (LVD) Reset option
Run and Power Saving modes
32 multifunctional bidirectional I/O lines:
– 9 programmable interrupt inputs
– 4 high sink outputs
– 13 alternate functions
– EMI filtering
Software or Hardware Watchdog (WDG)
Two 16-bit Timers, each featuring:
– 2 Input Captures and 2 Output Compares 1)
– External Clock input (on Timer A)
– PWM and Pulse Generator modes
Synchronous Serial Peripheral Interface (SPI)
Asynchronous Serial Communications Interface
(SCI)
8-bit Data Manipulation
63 basic Instructions and 17 main Addressing
Modes
8 x 8 Unsigned Multiply Instruction
True Bit Manipulation
Complete Development Support on DOS/
WINDOWSTM Real-Time Emulator
Full Software Package on DOS/WINDOWSTM
(C-Compiler, Cross-Assembler, Debugger)
PSDIP42
CSDIP42W
TQFP44
(See ordering information at the end of datasheet)
Note: 1. One only of each on Timer A.
Device Summary
Features
ST72T121J2
ST72T121J4
Program Memory - bytes
8K
16K
RAM (stack) - bytes
384 (256)
512 (256)
Peripherals
Watchdog, Timers, SPI, SCI and optional Low Voltage Detector Reset
Operating Supply
3 to 5.5 V
CPU Frequency
8MHz max (16MHz oscillator) - 4MHz max over 85°C
Temperature Range
- 40°C to + 125°C
Package
TQFP44 - SDIP42
OTP/EPROM Devices
ST72T121J4/ST72E121J4
Note: ROM versions are supported by the ST72334/124 family. Important product differences must be taken into account.
Refer to the Preamble in the ST72334/124 Datasheet for more information.
Revision 1.9
May 2001
1/93
1
Table of Contents
1 GENERAL DESCRIPTION . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4
1.1 INTRODUCTION . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4
1.2 PIN DESCRIPTION . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5
1.3 EXTERNAL CONNECTIONS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7
1.4 MEMORY MAP . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8
1.5 OPTION BYTE . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11
2 CENTRAL PROCESSING UNIT . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12
2.1 INTRODUCTION . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12
2.2 MAIN FEATURES . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12
2.3 CPU REGISTERS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12
3 CLOCKS, RESET, INTERRUPTS & POWER SAVING MODES . . . . . . . . . . . . . . . . . . . . . . . . 15
3.1 CLOCK SYSTEM . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15
3.1.1 General Description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15
3.1.2 External Clock . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15
3.2 RESET . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16
3.2.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
3.2.2 External Reset . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
3.2.3 Reset Operation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
3.2.4 Low Voltage Detector Reset . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
4 INTERRUPTS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
4.1 NON MASKABLE SOFTWARE INTERRUPT . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
16
16
16
17
18
18
4.2 EXTERNAL INTERRUPTS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18
4.3 PERIPHERAL INTERRUPTS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18
4.4 POWER SAVING MODES . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21
4.4.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
4.4.2 Slow Mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
4.4.3 Wait Mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
4.4.4 Halt Mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
4.5 MISCELLANEOUS REGISTER . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
21
21
21
22
23
5 ON-CHIP PERIPHERALS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 24
5.1 I/O PORTS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 24
5.1.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
5.1.2 Functional Description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
5.1.3 I/O Port Implementation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
5.1.4 Register Description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
5.2 WATCHDOG TIMER (WDG) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
24
24
25
28
30
5.2.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
5.2.2 Main Features . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
5.2.3 Functional Description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
5.2.4 Hardware Watchdog Option . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
5.2.5 Low Power Modes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
5.2.6 Interrupts . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
5.2.7 Register Description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
93
5.3 16-BIT TIMER . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
30
30
30
31
31
31
31
33
5.3.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 33
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Table of Contents
5.3.2 Main Features . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
5.3.3 Functional Description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
5.3.4 Low Power Modes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
5.3.5 Interrupts . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
5.3.6 Summary of Timer modes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
5.3.7 Register Description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
5.4 SERIAL COMMUNICATIONS INTERFACE (SCI) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
33
33
45
45
45
46
51
5.4.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
5.4.2 Main Features . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
5.4.3 General Description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
5.4.4 Functional Description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
5.4.5 Low Power Modes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
5.4.6 Interrupts . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
5.4.7 Register Description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
5.5 SERIAL PERIPHERAL INTERFACE (SPI) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
51
51
51
53
58
58
59
63
5.5.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
5.5.2 Main Features . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
5.5.3 General description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
5.5.4 Functional Description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
5.5.5 Low Power Modes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
5.5.6 Interrupts . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
5.5.7 Register Description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
6 INSTRUCTION SET . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
6.1 ST7 ADDRESSING MODES . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
63
63
63
65
72
72
73
76
76
6.1.1 Inherent . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
6.1.2 Immediate . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
6.1.3 Direct . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
6.1.4 Indexed (No Offset, Short, Long) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
6.1.5 Indirect (Short, Long) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
6.1.6 Indirect Indexed (Short, Long) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
6.1.7 Relative Mode (Direct, Indirect) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
6.2 INSTRUCTION GROUPS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
77
77
77
77
77
78
78
79
7 ELECTRICAL CHARACTERISTICS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 82
7.1 ABSOLUTE MAXIMUM RATINGS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 82
7.2 RECOMMENDED OPERATING CONDITIONS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 83
7.3 DC ELECTRICAL CHARACTERISTICS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 84
7.4 RESET CHARACTERISTICS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 85
7.5 OSCILLATOR CHARACTERISTICS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 85
7.6 PERIPHERAL CHARACTERISTICS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 85
8 GENERAL INFORMATION . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 89
8.1 EPROM ERASURE . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 89
8.2 PACKAGE MECHANICAL DATA . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 90
8.3 ORDERING INFORMATION . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 92
9 SUMMARY OF CHANGES . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 93
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ST72E121 ST72T121
1 GENERAL DESCRIPTION
1.1 INTRODUCTION
The ST72T121 HCMOS Microcontroller Unit
(MCU) is a member of the ST7 family. The device
is based on an industry-standard 8-bit core and
features an enhanced instruction set. The device
is normally operated at a 16 MHz oscillator frequency. Under software control, the ST72T121
may be placed in either Wait, Slow or Halt modes,
thus reducing power consumption. The enhanced
instruction set and addressing modes afford real
programming potential. In addition to standard
8-bit data management, the ST72T121 features
true bit manipulation, 8x8 unsigned multiplication
and indirect addressing modes on the whole memory. The device includes a low consumption and
fast start on-chip oscillator, CPU, program memory (OTP/EPROM versions), RAM, 32 I/O lines, a
Low Voltage Detector (LVD) and the following onchip peripherals: industry standard synchronous
SPI and asynchronous SCI serial interfaces, digital Watchdog, two independent 16-bit Timers, one
featuring an External Clock Input, and both featuring Pulse Generator capabilities, 2 Input Captures
and 2 Output Compares (only 1 Input Capture and
1 Output Compare on Timer A).
Figure 1. ST72T121 Block Diagram
OSCIN
Internal
CLOCK
OSC
PORT A
PA3 -> PA7
(5 bits)
CONTROL
AND LVD
PORT B
PB0 -> PB4
(5 bits)
OSCOUT
RESET
8-BIT CORE
ALU
RAM
(384 - 512 Bytes)
ADDRESS AND DATA BUS
PROGRAM
MEMORY
(8 - 16K Bytes)
TIMER B
PORT C
PC0 -> PC7
(8 bits)
SPI
PORT D
PD0 -> PD5
(6 bits)
PORT E
PF0 -> PF2,4,6,7
(6 bits)
PORT F
SCI
TIMER A
VDD
VSS
4/93
4
POWER
SUPPLY
WATCHDOG
PE0 -> PE1
(2 bits)
ST72E121 ST72T121
1.2 PIN DESCRIPTION
44 43 42 41 40 39 38 37 36 35 34
33
1
32
2 (EI2)
(EI0) 31
3 (EI2)
30
4 (EI2)
29
5 (EI2)
28
6 (EI3)
1. V
PP
VSS_1
VDD_1
PA3
PC7/SS
PC6/SCK
PC5/MOSI
PC4/MISO
PC3/ICAP1_B
PC2/ICAP2_B
PC1/OCMP1_B
PC0/OCMP2_B
CLKOUT/PF0
PF1
PF2
OCMP1_A/PF4
ICAP1_A/PF6
EXTCLK_A/PF7
VDD_0
VSS_0
(EI1)
(EI1)
(EI1)
27
7
26
8
25
9
24
10
23
11
12 13 14 15 16 17 18 19 20 21 22
PD5
VDD_3
VSS_3
PE1/RDI
PB0
PB1
PB2
PB3
PB4
PD0
PD1
PD2
PD3
PD4
RESET
TEST/VPP1)
PA7
PA6
PA5
PA4
PE0/TD0
VDD_2
OSCIN
OSCOUT
VSS_2
Figure 2. 44-Pin Thin QFP Package Pinout
on EPROM/OTP only
Figure 3. 42-Pin Shrink DIP Package Pinout
PB4
PD0
PD1
PD2
PD3
PD4
PD5
VDD_3
VSS_3
CLKOUT/PF0
PF1
PF2
OCMP1_A/PF4
ICAP1_A/PF6
EXTCLK_A/PF7
PC0/OCMP2_B
PC1/OCMP1_B
PC2/ICAP2_B
PC3/ICAP1_B
PC4/MISO
PC5/MOSI
1. V
PP
1 (EI3)
2
3
4
5
6
7
8
9
10 (EI1)
11 (EI1)
12 (EI1)
13
14
15
16
17
18
19
20
21
42
41
40
39
38
37
36
35
34
33
32
31
30
29
28
27
26
25
(EI0)24
23
22
(EI2)
(EI2)
(EI2)
(EI2)
PB3
PB2
PB1
PB0
PE1/RDI
PE0/TD0
VDD_2
OSCIN
OSCOUT
VSS_2
RESET
TEST/VPP1)
PA7
PA6
PA5
PA4
VSS_1
VDD_1
PA3
PC7/SS
PC6/SCK
on EPROM/OTP only
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5
ST72E121 ST72T121
Table 1. ST72T121Jx Pin Description
Pin n° Pin n°
QFP44 SDIP42
Pin Name
Description
Remarks
1
38
PE1/RDI
I/O
Port E1 or SCI Receive Data In
2
39
PB0
I/O
Port B0
External Interrupt: EI2
3
40
PB1
I/O
Port B1
External Interrupt: EI2
4
41
PB2
I/O
Port B2
External Interrupt: EI2
5
42
PB3
I/O
Port B3
External Interrupt: EI2
6
1
PB4
I/O
Port B4
External Interrupt: EI3
7
2
PD0
I/O
Port D0
8
3
PD1
I/O
Port D1
9
4
PD2
I/O
Port D2
10
5
PD3
I/O
Port D3
11
6
PD4
I/O
Port D4
12
7
PD5
I/O
Port D5
13
8
VDD_3
S
Main Power Supply
14
9
VSS_3
S
Ground
15
10
PF0/CLKOUT
I/O
Port F0 or CPU Clock Output
External Interrupt: EI1
16
11
PF1
I/O
Port F1
External Interrupt: EI1
External Interrupt: EI1
17
12
PF2
I/O
Port F2
18
13
PF4/OCMP1_A
I/O
Port F4 or Timer A Output Compare 1
19
14
PF6/ICAP1_A
I/O
Port F6 or Timer A Input Capture 1
20
15
PF7/EXTCLK_A
I/O
Port F7 or External Clock on Timer A
21
VDD_0
S
Main power supply
22
VSS_0
S
Ground
Port C0 or Timer B Output Compare 2
23
16
PC0/OCMP2_B
I/O
24
17
PC1/OCMP1_B
I/O
Port C1 or Timer B Output Compare 1
25
18
PC2/ICAP2_B
I/O
Port C2 or Timer B Input Capture 2
26
19
PC3/ICAP1_B
I/O
Port C3 or Timer B Input Capture 1
27
20
PC4/MISO
I/O
Port C4 or SPI Master In / Slave Out Data
28
21
PC5/MOSI
I/O
Port C5 or SPI Master Out / Slave In Data
29
22
PC6/SCK
I/O
Port C6 or SPI Serial Clock
30
23
PC7/SS
I/O
Port C7 or SPI Slave Select
31
24
PA3
I/O
Port A3
32
25
VDD_1
S
Main power supply
33
26
VSS_1
S
Ground
34
27
PA4
I/O
Port A4
High Sink
35
28
PA5
I/O
Port A5
High Sink
36
29
PA6
I/O
Port A6
High Sink
37
30
PA7
I/O
Port A7
High Sink
TEST/VPP1)
S
Test mode pin. In the EPROM programming
mode, this pin acts as the programming voltage
input VPP.
This pin must be tied low
in user mode
38
31
External Interrupt: EI0
39
32
RESET
I/O
Bidirectional. Active low. Top priority non maskable interrupt.
40
33
VSS_2
S
Ground
41
34
OSCOUT
O
42
35
OSCIN
I
Input/Output Oscillator pin. These pins connect a parallel-resonant crystal, or
an external source to the on-chip oscillator.
43
36
VDD_2
S
Main power supply
44
37
PE0/TDO
I/O
Port E0 or SCI Transmit Data Out
Note 1: VPP on EPROM/OTP only.
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6
Type
ST72E121 ST72T121
1.3 EXTERNAL CONNECTIONS
The following figure shows the recommended external connections for the device.
The VPP pin is only used for programming OTP
and EPROM devices and must be tied to ground in
user mode.
The 10 nF and 0.1 µF decoupling capacitors on
the power supply lines are a suggested EMC performance/cost tradeoff.
The external reset network is intended to protect
the device against parasitic resets, especially in
noisy environments.
Unused I/Os should be tied high to avoid any unnecessary power consumption on floating lines.
An alternative solution is to program the unused
ports as inputs with pull-up.
Figure 4. Recommended External Connections
VPP
VDD
10nF
VDD
+
0.1µF
VSS
Optional if Low Voltage
Detector (LVD) is used
VDD
4.7K
0.1µF
RESET
EXTERNAL RESET CIRCUIT
0.1µF
See
Clocks
Section
OSCIN
OSCOUT
Or configure unused I/O ports
by software as input with pull-up
VDD
10K
Unused I/O
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ST72E121 ST72T121
1.4 MEMORY MAP
Figure 5. Program Memory Map
0080h
Short Addressing
RAM (zero page)
0000h
HW Registers
(see Table 3)
00FFh
0100h
007Fh
0080h
256 Bytes Stack/
16-bit Addressing RAM
01FFh
384 Bytes RAM
01FFh
027Fh
512 Bytes RAM
0200h / 0280h
0080h
00FFh
Reserved
Short Addressing
RAM (zero page)
0100h
256 Bytes Stack/
BFFFh
16-bit Addressing RAM
C000h
E000h
FFDFh
FFE0h
FFFFh
8K Bytes
Program
Memory
01FFh
16K Bytes
Program
Memory
0200h
027Fh
16-bit Addressing
RAM
Interrupt & Reset Vectors
(see Table 2)
Table 2. Interrupt Vector Map
8/93
8
Vector Address
Description
FFE0-FFE1h
Not Used
FFE2-FFE3h
Not Used
FFE4-FFE5h
Not Used
Internal Interrupt
FFE6-FFE7h
SCI Interrupt Vector
Internal Interrupt
FFE8-FFE9h
TIMER B Interrupt Vector
Internal Interrupt
FFEA-FFEBh
TIMER A Interrupt Vector
Internal Interrupt
FFEC-FFEDh
SPI interrupt vector
Internal Interrupt
FFEE-FFEFh
Not Used
FFF0-FFF1h
External Interrupt Vector EI3 (PB4)
External Interrupt
FFF2-FFF3h
External Interrupt Vector EI2 (PB0:PB3)
External Interrupt
FFF4-FFF5h
External Interrupt Vector EI1 (PF0:PF2)
External Interrupt
FFF6-FFF7h
External Interrupt Vector EI0 (PA3)
External Interrupt
FFF8-FFF9h
Not Used
FFFA-FFFBh
Not Used
FFFC-FFFDh
TRAP (software) Interrupt Vector
FFFE-FFFFh
RESET Vector
Remarks
CPU Interrupt
ST72E121 ST72T121
Table 3. Hardware Register Memory Map
Address
0000h
0001h
0002h
0003h
0004h
0005h
0006h
0007h
0008h
0009h
000Ah
000Bh
000Ch
000Dh
000Eh
000Fh
0010h
0011h
0012h
0013h
0014h
0015h
0016h
0017h to
001Fh
0020h
0021h
0022h
0023h
0024h to
0029h
002Ah
002Bh
002Ch to
0030h
Block
Register
Label
Port A
PADR
PADDR
PAOR
Port C
PCDR
PCDDR
PCOR
Port B
PBDR
PBDDR
PBOR
Port E
PEDR
PEDDR
PEOR
Port D
PDDR
PDDDR
PDOR
Port F
PFDR
PFDDR
PFOR
Register Name
Data Register
Data Direction Register
Option Register
Reserved Area
Data Register
Data Direction Register
Option Register
Reserved Area
Data Register
Data Direction Register
Option Register
Reserved Area
Data Register
Data Direction Register
Option Register
Reserved Area
Data Register
Data Direction Register
Option Register
Reserved Area
Data Register
Data Direction Register
Option Register
Reset
Status
Remarks
00h
00h
00h
R/W
R/W
R/W 1)
00h
00h
00h
R/W
R/W
R/W
00h
00h
00h
R/W
R/W
R/W 1)
00h
00h
0Ch
R/W
R/W
R/W 1)
00h
00h
00h
R/W
R/W
R/W 1)
00h
00h
28h
R/W
R/W
R/W 1)
00h
xxh
xxh
00h
R/W
R/W
Read Only
(1 byte)
(1 byte)
(1 byte)
(1 byte)
(1 byte)
Reserved Area (9 bytes)
SPI
MISCR
SPIDR
SPICR
SPISR
Miscellaneous Register
SPI Data I/O Register
SPI Control Register
SPI Status Register
Reserved Area (6 bytes)
WDG
WDGCR
Watchdog Control Register
7Fh
R/W
WDGSR
Watchdog Status Register
00h
R/W3)
Reserved Area (5 bytes)
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9
ST72E121 ST72T121
Address
Block
Register
Label
Timer A
TACR2
TACR1
TASR
TAIC1HR
TAIC1LR
TAOC1HR
TAOC1LR
TACHR
TACLR
TAACHR
TAACLR
TAIC2HR
TAIC2LR
TAOC2HR
TAOC2LR
0031h
0032h
0033h
0034h-0035h
0036h-0037h
0038h-0039h
003Ah-003Bh
003Ch-003Dh
003Eh-003Fh
0040h
0041h
0042h
0043h
0044h-0045h
0046h-0047h
0048h-0049h
Timer B
004Ah-004Bh
004Ch-004Dh
004Eh-004Fh
0050h
0051h
0052h
0053h
0054h
0055h
0056h
0057h
0058h to
007Fh
SCI
TBCR2
TBCR1
TBSR
TBIC1HR
TBIC1LR
TBOC1HR
TBOC1LR
TBCHR
TBCLR
TBACHR
TBACLR
TBIC2HR
TBIC2LR
TBOC2HR
TBOC2LR
SCISR
SCIDR
SCIBRR
SCICR1
SCICR2
SCIERPR
SCIETPR
Register Name
Control Register2
Control Register1
Status Register
Input Capture1 High Register
Input Capture1 Low Register
Output Compare1 High Register
Output Compare1 Low Register
Counter High Register
Counter Low Register
Alternate Counter High Register
Alternate Counter Low Register
Input Capture2 High Register
Input Capture2 Low Register
Output Compare2 High Register
Output Compare2 Low Register
Reserved Area (1 byte)
Control Register2
Control Register1
Status Register
Input Capture1 High Register
Input Capture1 Low Register
Output Compare1 High Register
Output Compare1 Low Register
Counter High Register
Counter Low Register
Alternate Counter High Register
Alternate Counter Low Register
Input Capture2 High Register
Input Capture2 Low Register
Output Compare2 High Register
Output Compare2 Low Register
SCI Status Register
SCI Data Register
SCI Baud Rate Register
SCI Control Register 1
SCI Control Register 2
SCI Extended Receive Prescaler Register
Reserved
SCI Extended Transmit Prescaler Register
Reset
Status
00h
00h
xxh
xxh
xxh
80h
00h
FFh
FCh
FFh
FCh
xxh
xxh
80h
00h
00h
00h
xxh
xxh
xxh
80h
00h
FFh
FCh
FFh
FCh
xxh
xxh
80h
00h
C0h
xxh
00x----xb
xxh
00h
00h
--00h
Remarks
R/W
R/W
Read Only
Read Only
Read Only
R/W
R/W
Read Only
Read Only
Read Only
Read Only
Read Only2)
Read Only2)
R/W2)
R/W2)
R/W
R/W
Read Only
Read Only
Read Only
R/W
R/W
Read Only
Read Only
Read Only
Read Only
Read Only
Read Only
R/W
R/W
Read Only
R/W
R/W
R/W
R/W
R/W
Reserved
R/W
Reserved Area (40 bytes)
Notes:
1. The bits corresponding to unavailable pins are forced to 1 by hardware, this affects the reset status value.
2. External pin not available.
3. Not used in versions without Low Voltage Detector Reset.
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ST72E121 ST72T121
1.5 OPTION BYTE
The user has the option to select software watchdog or hardware watchdog (see description in the
Watchdog chapter). When programming EPROM
or OTP devices, this option is selected in a menu
by the user of the EPROM programmer before
burning the EPROM/OTP. The Option Byte is located in a non-user map. No address has to be
specified. The Option Byte is at FFh after UV erasure and must be properly programmed to set desired options.
OPTBYTE
7
-
0
-
-
-
b3
b2
-
WDG
Bit 7:4 = Not used
Bit 3 = Reserved, must be cleared.
Bit 2 = Reserved, must be set on ST72T121N devices and must be cleared on ST72T121J devices.
Bit 1 = Not used
Bit 0 = WDG Watchdog disable
0: The Watchdog is enabled after reset (Hardware
Watchdog).
1: The Watchdog is not enabled after reset (Software Watchdog).
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ST72E121 ST72T121
2 CENTRAL PROCESSING UNIT
2.1 INTRODUCTION
This CPU has a full 8-bit architecture and contains
six internal registers allowing efficient 8-bit data
manipulation.
2.2 MAIN FEATURES
■
■
■
■
■
■
■
■
63 basic instructions
Fast 8-bit by 8-bit multiply
17 main addressing modes
Two 8-bit index registers
16-bit stack pointer
Low power modes
Maskable hardware interrupts
Non-maskable software interrupt
2.3 CPU REGISTERS
The 6 CPU registers shown in Figure 6 are not
present in the memory mapping and are accessed
by specific instructions.
Accumulator (A)
The Accumulator is an 8-bit general purpose register used to hold operands and the results of the
arithmetic and logic calculations and to manipulate
data.
Index Registers (X and Y)
In indexed addressing modes, these 8-bit registers
are used to create either effective addresses or
temporary storage areas for data manipulation.
(The Cross-Assembler generates a precede instruction (PRE) to indicate that the following instruction refers to the Y register.)
The Y register is not affected by the interrupt automatic procedures (not pushed to and popped from
the stack).
Program Counter (PC)
The program counter is a 16-bit register containing
the address of the next instruction to be executed
by the CPU. It is made of two 8-bit registers PCL
(Program Counter Low which is the LSB) and PCH
(Program Counter High which is the MSB).
Figure 6. CPU Registers
7
0
ACCUMULATOR
RESET VALUE = XXh
7
0
X INDEX REGISTER
RESET VALUE = XXh
7
0
Y INDEX REGISTER
RESET VALUE = XXh
15
PCH
8 7
PCL
0
PROGRAM COUNTER
RESET VALUE = RESET VECTOR @ FFFEh-FFFFh
7
1 1 1 H I
0
N Z C
CONDITION CODE REGISTER
RESET VALUE = 1 1 1 X 1 X X X
15
8 7
0
STACK POINTER
RESET VALUE = STACK HIGHER ADDRESS
X = Undefined Value
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12
ST72E121 ST72T121
CPU REGISTERS (Cont’d)
CONDITION CODE REGISTER (CC)
Read/Write
Reset Value: 111x1xxx
7
1
0
1
1
H
I
N
Z
because the I bit is set by hardware at the start of
the routine and reset by the IRET instruction at the
end of the routine. If the I bit is cleared by software
in the interrupt routine, pending interrupts are
serviced regardless of the priority level of the current interrupt routine.
C
The 8-bit Condition Code register contains the interrupt mask and four flags representative of the
result of the instruction just executed. This register
can also be handled by the PUSH and POP instructions.
These bits can be individually tested and/or controlled by specific instructions.
Bit 4 = H Half carry.
This bit is set by hardware when a carry occurs between bits 3 and 4 of the ALU during an ADD or
ADC instruction. It is reset by hardware during the
same instructions.
0: No half carry has occurred.
1: A half carry has occurred.
This bit is tested using the JRH or JRNH instruction. The H bit is useful in BCD arithmetic subroutines.
Bit 2 = N Negative.
This bit is set and cleared by hardware. It is representative of the result sign of the last arithmetic,
logical or data manipulation. It is a copy of the 7th
bit of the result.
0: The result of the last operation is positive or null.
1: The result of the last operation is negative
(i.e. the most significant bit is a logic 1).
This bit is accessed by the JRMI and JRPL instructions.
Bit 1 = Z Zero.
This bit is set and cleared by hardware. This bit indicates that the result of the last arithmetic, logical
or data manipulation is zero.
0: The result of the last operation is different from
zero.
1: The result of the last operation is zero.
This bit is accessed by the JREQ and JRNE test
instructions.
Bit 3 = I Interrupt mask.
This bit is set by hardware when entering in interrupt or by software to disable all interrupts except
the TRAP software interrupt. This bit is cleared by
software.
0: Interrupts are enabled.
1: Interrupts are disabled.
This bit is controlled by the RIM, SIM and IRET instructions and is tested by the JRM and JRNM instructions.
Note: Interrupts requested while I is set are
latched and can be processed when I is cleared.
By default an interrupt routine is not interruptable
Bit 0 = C Carry/borrow.
This bit is set and cleared by hardware and software. It indicates an overflow or an underflow has
occurred during the last arithmetic operation.
0: No overflow or underflow has occurred.
1: An overflow or underflow has occurred.
This bit is driven by the SCF and RCF instructions
and tested by the JRC and JRNC instructions. It is
also affected by the “bit test and branch”, shift and
rotate instructions.
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ST72E121 ST72T121
CENTRAL PROCESSING UNIT (Cont’d)
Stack Pointer (SP)
Read/Write
Reset Value: 01FFh
15
0
8
0
0
0
0
0
0
7
SP7
1
0
SP6
SP5
SP4
SP3
SP2
SP1
SP0
The Stack Pointer is a 16-bit register which is always pointing to the next free location in the stack.
It is then decremented after data has been pushed
onto the stack and incremented before data is
popped from the stack (see Figure 7).
Since the stack is 256 bytes deep, the 8th most
significant bits are forced by hardware. Following
an MCU Reset, or after a Reset Stack Pointer instruction (RSP), the Stack Pointer contains its reset value (the SP7 to SP0 bits are set) which is the
stack higher address.
The least significant byte of the Stack Pointer
(called S) can be directly accessed by a LD instruction.
Note: When the lower limit is exceeded, the Stack
Pointer wraps around to the stack upper limit, without indicating the stack overflow. The previously
stored information is then overwritten and therefore lost. The stack also wraps in case of an underflow.
The stack is used to save the return address during a subroutine call and the CPU context during
an interrupt. The user may also directly manipulate
the stack by means of the PUSH and POP instructions. In the case of an interrupt, the PCL is stored
at the first location pointed to by the SP. Then the
other registers are stored in the next locations as
shown in Figure 7.
– When an interrupt is received, the SP is decremented and the context is pushed on the stack.
– On return from interrupt, the SP is incremented
and the context is popped from the stack.
A subroutine call occupies two locations and an interrupt five locations in the stack area.
Figure 7. Stack Manipulation Example
CALL
Subroutine
PUSH Y
Interrupt
Event
POP Y
RET
or RSP
IRET
@ 0100h
SP
SP
CC
A
X
X
X
PCH
PCH
PCH
PCL
PCL
PCL
PCH
PCH
PCH
PCH
PCH
PCL
PCL
PCL
PCL
PCL
SP
@ 01FFh
Stack Higher Address = 01FFh
Stack Lower Address = 0100h
14/93
14
SP
Y
CC
A
CC
A
SP
SP
ST72E121 ST72T121
3 CLOCKS, RESET, INTERRUPTS & POWER SAVING MODES
3.1 CLOCK SYSTEM
3.1.1 General Description
The MCU accepts either a crystal or ceramic resonator, or an external clock signal to drive the internal oscillator. The internal clock (f CPU) is derived
from the external oscillator frequency (fOSC). The
external Oscillator clock is first divided by 2, and
an additional division factor of 2, 4, 8, or 16 can be
applied, in Slow Mode, to reduce the frequency of
the fCPU; this clock signal is also routed to the onchip peripherals. The CPU clock signal consists of
a square wave with a duty cycle of 50%.
The internal oscillator is designed to operate with
an AT-cut parallel resonant quartz crystal resonator in the frequency range specified for fosc. The
circuit shown in Figure 9 is recommended when
using a crystal, and Table 4 lists the recommended capacitance and feedback resistance values.
The crystal and associated components should be
mounted as close as possible to the input pins in
order to minimize output distortion and start-up
stabilisation time.
Use of an external CMOS oscillator is recommended when crystals outside the specified frequency ranges are to be used.
3.1.2 External Clock
An external clock may be applied to the OSCIN input with the OSCOUT pin not connected, as
shown on Figure 8.
Figure 8. External Clock Source Connections
Table 4 Recommended Values for 16 MHz
Crystal Resonator (C0 < 7pF)
Figure 10. Clock Prescaler Block Diagram
RSMAX
40 Ω
60 Ω
150 Ω
COSCIN
56pF
47pF
22pF
COSCOUT
56pF
47pF
22pF
RSMAX: Parasitic series resistance of the quartz
crystal (upper limit).
C0: Parasitic shunt capacitance of the quartz crystal (upper limit 7pF).
COSCOUT, COSCIN: Maximum total capacitance on
pins OSCIN and OSCOUT (the value includes the
external capacitance tied to the pin plus the parasitic capacitance of the board and of the device).
OSCIN
OSCOUT
NC
EXTERNAL
CLOCK
Figure 9. Crystal/Ceramic Resonator
OSCIN
OSCOUT
COSCIN
COSCOUT
%2
OSCIN
COSCIN
OSCOUT
% 2, 4, 8, 16
fCPU
to CPU and
Peripherals
COSCOUT
15/93
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ST72E121 ST72T121
3.2 RESET
3.2.1 Introduction
There are four sources of Reset:
– RESET pin (external source)
– Power-On Reset (Internal source)
– WATCHDOG (Internal Source)
– Low Voltage Detection Reset (internal source)
The Reset Service Routine vector is located at address FFFEh-FFFFh.
3.2.2 External Reset
The RESET pin is both an input and an open-drain
output with integrated pull-up resistor. When one
of the internal Reset sources is active, the Reset
pin is driven low for a duration of tRESET to reset
the whole application.
3.2.3 Reset Operation
The duration of the Reset state is a minimum of
4096 internal CPU Clock cycles. During the Reset
state, all I/Os take their reset value.
A Reset signal originating from an external source
must have a duration of at least tPULSE in order to
be recognised. This detection is asynchronous
and therefore the MCU can enter Reset state even
in Halt mode.
At the end of the Reset cycle, the MCU may be
held in the Reset state by an External Reset signal. The RESET pin may thus be used to ensure
VDD has risen to a point where the MCU can operate correctly before the user program is run. Following a Reset event, or after exiting Halt mode, a
4096 CPU Clock cycle delay period is initiated in
order to allow the oscillator to stabilise and to ensure that recovery has taken place from the Reset
state.
In the high state, the RESET pin is connected internally to a pull-up resistor (RON). This resistor
can be pulled low by external circuitry to reset the
device.
The RESET pin is an asynchronous signal which
plays a major role in EMS performance. In a noisy
environment, it is recommended to use the external connections shown in Figure 4.
Figure 11. Reset Block Diagram
INTERNAL
TO ST7
RESET
COUNTER
RESET
OSCILLATOR
SIGNAL
RESET
VDD
RON
POWER-ON RESET
WATCHDOG RESET
LOW VOLTAGE DETECTOR RESET
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ST72E121 ST72T121
RESET (Cont’d)
3.2.4 Low Voltage Detector Reset
The on-chip Low Voltage Detector (LVD) generates a static reset when the supply voltage is below a reference value. The LVD functions both
during power-on as well as when the power supply
drops (brown-out). The reference value for a voltage drop is lower than the reference value for power-on in order to avoid a parasitic reset when the
MCU starts running and sinks current on the supply (hysteresis).
The LVD Reset circuitry generates a reset when
VDD is below:
VLVDUP when VDD is rising
VLVDDOWN when VDD is falling
Provided the minimun VDD value (guaranteed for
the oscillator frequency) is above VLVDDOWN , the
MCU can only be in two modes:
- under full software control or
- in static safe reset
In this condition, secure operation is always ensured for the application without the need for external reset hardware.
During a Low Voltage Detector Reset, the RESET
pin is held low, thus permitting the MCU to reset
other devices.
In noisy environments, the power supply may drop
for short periods and cause the Low Voltage Detector to generate a Reset too frequently. In such
cases, it is recommended to use devices without
the LVD Reset option and to rely on the watchdog
function to detect application runaway conditions.
Figure 12. Low Voltage Detector Reset Function
VDD
LOW VOLTAGE
DETECTOR RESET
FROM
WATCHDOG
RESET
RESET
Figure 13. Low Voltage Detector Reset Signal
VLVDUP
VLVDDOWN
VDD
RESET
Note: See electrical characteristics for values of
VLVDUP and V LVDDOWN
Figure 14. Temporization timing diagram after an internal Reset
VLVDUP
VDD
Temporization (4096 CPU clock cycles)
Addresses
$FFFE
17/93
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ST72E121 ST72T121
4 INTERRUPTS
The ST7 core may be interrupted by one of two different methods: maskable hardware interrupts as
listed in the Interrupt Mapping Table and a nonmaskable software interrupt (TRAP). The Interrupt
processing flowchart is shown in Figure 15.
The maskable interrupts must be enabled by
clearing the I bit in order to be serviced. However,
disabled interrupts may be latched and processed
when they are enabled (see external interrupts
subsection).
Note: After reset, all interrupts are disabled.
When an interrupt has to be serviced:
– Normal processing is suspended at the end of
the current instruction execution.
– The PC, X, A and CC registers are saved onto
the stack.
– The I bit of the CC register is set to prevent additional interrupts.
– The PC is then loaded with the interrupt vector of
the interrupt to service and the first instruction of
the interrupt service routine is fetched (refer to
the Interrupt Mapping Table for vector addresses).
The interrupt service routine should finish with the
IRET instruction which causes the contents of the
saved registers to be recovered from the stack.
Note: As a consequence of the IRET instruction,
the I bit will be cleared and the main program will
resume.
Priority Management
By default, a servicing interrupt cannot be interrupted because the I bit is set by hardware entering in interrupt routine.
In the case when several interrupts are simultaneously pending, an hardware priority defines which
one will be serviced first (see the Interrupt Mapping Table).
Interrupts and Low Power Mode
All interrupts allow the processor to leave the
WAIT low power mode. Only external and specifically mentioned interrupts allow the processor to
leave the HALT low power mode (refer to the “Exit
from HALT“ column in the Interrupt Mapping Table).
4.1 NON MASKABLE SOFTWARE INTERRUPT
This interrupt is entered when the TRAP instruction is executed regardless of the state of the I bit.
18/93
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It will be serviced according to the flowchart on
Figure 15.
4.2 EXTERNAL INTERRUPTS
External interrupt vectors can be loaded into the
PC register if the corresponding external interrupt
occurred and if the I bit is cleared. These interrupts
allow the processor to leave the Halt low power
mode.
The external interrupt polarity is selected through
the miscellaneous register or interrupt register (if
available).
An external interrupt triggered on edge will be
latched and the interrupt request automatically
cleared upon entering the interrupt service routine.
If several input pins, connected to the same interrupt vector, are configured as interrupts, their signals are logically ANDed and inverted before entering the edge/level detection block.
Caution: The type of sensitivity defined in the Miscellaneous or Interrupt register (if available) applies to the ei source. In case of an ANDed source
(as described on the I/O ports section), a low level
on an I/O pin configured as input with interrupt,
masks the interrupt request even in case of risingedge sensitivity.
4.3 PERIPHERAL INTERRUPTS
Different peripheral interrupt flags in the status
register are able to cause an interrupt when they
are active if both:
– The I bit of the CC register is cleared.
– The corresponding enable bit is set in the control
register.
If any of these two conditions is false, the interrupt
is latched and thus remains pending.
Clearing an interrupt request is done by:
– Writing “0” to the corresponding bit in the status
register or
– Access to the status register while the flag is set
followed by a read or write of an associated register.
Note: the clearing sequence resets the internal
latch. A pending interrupt (i.e. waiting for being enabled) will therefore be lost if the clear sequence is
executed.
ST72E121 ST72T121
INTERRUPTS (Cont’d)
Figure 15. Interrupt Processing Flowchart
FROM RESET
I BIT SET?
N
N
Y
Y
FETCH NEXT INSTRUCTION
N
IRET?
Y
INTERRUPT
PENDING?
STACK PC, X, A, CC
SET I BIT
LOAD PC FROM INTERRUPT VECTOR
EXECUTE INSTRUCTION
RESTORE PC, X, A, CC FROM STACK
THIS CLEARS I BIT BY DEFAULT
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ST72E121 ST72T121
Table 5. Interrupt Mapping
Source
Block
RESET
TRAP
EI0
EI1
EI2
EI3
SPI
TIMER A
TIMER B
SCI
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20
Description
Reset
Software
NOT USED
NOT USED
Ext. Interrupt (Ports PA0:PA3)
Ext. Interrupt (Ports PF0:PF2)
Ext. Interrupt (Ports PB0:PB3)
Ext. Interrupt (Ports PB4:PB7)
NOT USED
Transfer Complete
Mode Fault
Input Capture 1
Output Compare 1
Input Capture 2
Output Compare 2
Timer Overflow
Input Capture 1
Output Compare 1
Input Capture 2
Output Compare 2
Timer Overflow
Transmit Buffer Empty
Transmit Complete
Receive Buffer Full
Idle Line Detect
Overrun
NOT USED
NOT USED
NOT USED
Register
Label
Flag
N/A
N/A
N/A
N/A
N/A
N/A
N/A
N/A
N/A
N/A
N/A
N/A
SPISR
TASR
TBSR
SCISR
SPIF
MODF
ICF1_A
OCF1_A
ICF2_A
OCF2_A
TOF_A
ICF1_B
OCF1_B
ICF2_B
OCF2_B
TOF_B
TDRE
TC
RDRF
IDLE
OR
Exit
from
HALT
yes
no
yes
Vector
Address
FFFEh-FFFFh
FFFCh-FFFDh
FFFAh-FFFBh
FFF8h-FFF9h
FFF6h-FFF7h
FFF4h-FFF5h
FFF2h-FFF3h
FFF0h-FFF1h
FFEEh-FFEFh
Priority
Order
Highest
Priority
FFECh-FFEDh
FFEAh-FFEBh
no
FFE8h-FFE9h
FFE6h-FFE7h
Lowest
Priority
FFE4h-FFE5h
FFE2h-FFE3h
FFE0h-FFE1h
ST72E121 ST72T121
4.4 POWER SAVING MODES
4.4.1 Introduction
There are three Power Saving modes. Slow Mode
is selected by setting the relevant bits in the Miscellaneous register. Wait and Halt modes may be
entered using the WFI and HALT instructions.
Figure 16. WAIT Flow Chart
WFI INSTRUCTION
4.4.2 Slow Mode
In Slow mode, the oscillator frequency can be divided by a value defined in the Miscellaneous
Register. The CPU and peripherals are clocked at
this lower frequency. Slow mode is used to reduce
power consumption, and enables the user to adapt
clock frequency to available supply voltage.
4.4.3 Wait Mode
Wait mode places the MCU in a low power consumption mode by stopping the CPU. All peripherals remain active. During Wait mode, the I bit (CC
Register) is cleared, so as to enable all interrupts.
All other registers and memory remain unchanged.
The MCU will remain in Wait mode until an Interrupt or Reset occurs, whereupon the Program
Counter branches to the starting address of the Interrupt or Reset Service Routine.
The MCU will remain in Wait mode until a Reset or
an Interrupt occurs, causing it to wake up.
Refer to Figure 16 below.
OSCILLATOR
PERIPH. CLOCK
CPU CLOCK
I-BIT
ON
ON
OFF
CLEARED
N
RESET
N
Y
INTERRUPT
Y
OSCILLATOR
PERIPH. CLOCK
CPU CLOCK
I-BIT
ON
ON
ON
SET
4096 CPU CLOCK
CYCLES DELAY
OSCILLATOR
PERIPH. CLOCK
CPU CLOCK
I-BIT
ON
ON
ON
SET
FETCH RESET VECTOR
OR SERVICE INTERRUPT
Note: Before servicing an interrupt, the CC register is
pushed on the stack. The I-Bit is set during the interrupt routine and cleared when the CC register is
popped.
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ST72E121 ST72T121
POWER SAVING MODES (Cont’d)
4.4.4 Halt Mode
The Halt mode is the MCU lowest power consumption mode. The Halt mode is entered by executing the HALT instruction. The internal oscillator
is then turned off, causing all internal processing to
be stopped, including the operation of the on-chip
peripherals. The Halt mode cannot be used when
the watchdog is enabled, if the HALT instruction is
executed while the watchdog system is enabled, a
watchdog reset is generated thus resetting the entire MCU.
When entering Halt mode, the I bit in the CC Register is cleared so as to enable External Interrupts.
If an interrupt occurs, the CPU becomes active.
The MCU can exit the Halt mode upon reception of
an interrupt or a reset. Refer to the Interrupt Mapping Table. The oscillator is then turned on and a
stabilization time is provided before releasing CPU
operation. The stabilization time is 4096 CPU clock
cycles.
After the start up delay, the CPU continues operation by servicing the interrupt which wakes it up or
by fetching the reset vector if a reset wakes it up.
Figure 17. HALT Flow Chart
HALT INSTRUCTION
WATCHDOG
WDG
Y
ENABLED?
RESET
N
OSCILLATOR
PERIPH. CLOCK
CPU CLOCK
I-BIT
OFF
OFF
OFF
CLEARED
N
RESET
N
EXTERNAL
INTERRUPT1)
Y
Y
OSCILLATOR
PERIPH. CLOCK2)
CPU CLOCK
I-BIT
ON
OFF
ON
SET
4096 CPU CLOCK
CYCLES DELAY
OSCILLATOR
PERIPH. CLOCK
CPU CLOCK
I-BIT
ON
ON
ON
SET
FETCH RESET VECTOR
OR SERVICE INTERRUPT
1) or some specific interrupts
2) if reset PERIPH. CLOCK = ON ; if interrupt
PERIPH. CLOCK = OFF
Note: Before servicing an interrupt, the CC register is
pushed on the stack. The I-Bit is set during the interrupt routine and cleared when the CC register is
popped.
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ST72E121 ST72T121
4.5 MISCELLANEOUS REGISTER
The Miscellaneous register allows to select the
SLOW operating mode, the polarity of external interrupt requests and to output the internal clock.
Register Address: 0020h — Read /Write
Reset Value: 0000 0000 (00h)
7
0
PEI3 PEI2 MCO PEI1 PEI0 PSM1 PSM0 SMS
Bit 7:6 = PEI[3:2] External Interrupt EI3 and EI2
Polarity Options.
These bits are set and cleared by software. They
determine which event on EI2 and EI3 causes the
external interrupt according to Table 6.
Table 6. EI2 and EI3 External Interrupt Polarity
Options
MODE
PEI3
PEI2
Falling edge and low level
(Reset state)
0
0
Bit 4:3 = PEI[1:0] External Interrupt EI1 and EI0
Polarity Options.
These bits are set and cleared by software. They
determine which event on EI0 and EI1 causes the
external interrupt according to Table 7.
Table 7. EI0 and EI1 External Interrupt Polarity
Options
MODE
PEI1
PEI0
Falling edge and low level
(Reset state)
0
0
Falling edge only
1
0
Rising edge only
0
1
Rising and falling edge
1
1
Note: Any modification of one of these two bits resets the interrupt request related to this interrupt
vector.l
Falling edge only
1
0
Rising edge only
0
1
Bit 2:1 = PSM[1:0] Prescaler for Slow Mode.
These bits are set and cleared by software. They
determine the CPU clock when the SMS bit is set
according to the following table.
Rising and falling edge
1
1
Table 8. fCPU Value in Slow Mode
Note: Any modification of one of these two bits resets the interrupt request related to this interrupt
vector.
Bit 5 = MCO Main Clock Out
This bit is set and cleared by software. When set, it
enables the output of the Internal Clock on the
PPF0 I/O port.
0 - PF0 is a general purpose I/O port.
1 - MCO alternate function (fCPU is output on PF0
pin).
fCPU Value
PSM1
PSM0
fOSC / 4
0
0
fOSC / 16
0
1
fOSC / 8
1
0
fOSC / 32
1
1
Bit 0 = SMS Slow Mode Select
This bit is set and cleared by software.
0: Normal Mode - fCPU = fOSC/ 2
(Reset state)
1: Slow Mode - the fCPU value is determined by the
PSM[1:0] bits.
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ST72E121 ST72T121
5 ON-CHIP PERIPHERALS
5.1 I/O PORTS
5.1.1 Introduction
The I/O ports offer different functional modes:
– transfer of data through digital inputs and outputs
and for specific pins:
– analog signal input (ADC)
– alternate signal input/output for the on-chip peripherals.
– external interrupt generation
An I/O port is composed of up to 8 pins. Each pin
can be programmed independently as digital input
(with or without interrupt generation) or digital output.
5.1.2 Functional Description
Each port is associated to 2 main registers:
– Data Register (DR)
– Data Direction Register (DDR)
and some of them to an optional register:
– Option Register (OR)
Each I/O pin may be programmed using the corresponding register bits in DDR and OR registers: bit
X corresponding to pin X of the port. The same correspondence is used for the DR register.
The following description takes into account the
OR register, for specific ports which do not provide
this register refer to the I/O Port Implementation
Section 5.1.3. The generic I/O block diagram is
shown on Figure 19.
5.1.2.1 Input Modes
The input configuration is selected by clearing the
corresponding DDR register bit.
In this case, reading the DR register returns the
digital value applied to the external I/O pin.
Different input modes can be selected by software
through the OR register.
Notes:
1. All the inputs are triggered by a Schmitt trigger.
2. When switching from input mode to output
mode, the DR register should be written first to
output the correct value as soon as the port is configured as an output.
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Interrupt function
When an I/O is configured in Input with Interrupt,
an event on this I/O can generate an external Interrupt request to the CPU. The interrupt polarity is
given independently according to the description
mentioned in the Miscellaneous register or in the
interrupt register (where available).
Each pin can independently generate an Interrupt
request.
Each external interrupt vector is linked to a dedicated group of I/O port pins (see Interrupts section). If several input pins are configured as inputs
to the same interrupt vector, their signals are logically ANDed before entering the edge/level detection block. For this reason if one of the interrupt
pins is tied low, it masks the other ones.
5.1.2.2 Output Mode
The pin is configured in output mode by setting the
corresponding DDR register bit.
In this mode, writing “0” or “1” to the DR register
applies this digital value to the I/O pin through the
latch. Then reading the DR register returns the
previously stored value.
Note: In this mode, the interrupt function is disabled.
5.1.2.3 Digital Alternate Function
When an on-chip peripheral is configured to use a
pin, the alternate function is automatically selected. This alternate function takes priority over
standard I/O programming. When the signal is
coming from an on-chip peripheral, the I/O pin is
automatically configured in output mode (push-pull
or open drain according to the peripheral).
When the signal is going to an on-chip peripheral,
the I/O pin has to be configured in input mode. In
this case, the pin’s state is also digitally readable
by addressing the DR register.
Notes:
1. Input pull-up configuration can cause an unexpected value at the input of the alternate peripheral input.
2. When the on-chip peripheral uses a pin as input
and output, this pin must be configured as an input
(DDR = 0).
Warning: The alternate function must not be activated as long as the pin is configured as input with
interrupt, in order to avoid generating spurious interrupts.
ST72E121 ST72T121
I/O PORTS (Cont’d)
5.1.2.4 Analog Alternate Function
When the pin is used as an ADC input the I/O must
be configured as input, floating. The analog multiplexer (controlled by the ADC registers) switches
the analog voltage present on the selected pin to
the common analog rail which is connected to the
ADC input.
It is recommended not to change the voltage level
or loading on any port pin while conversion is in
progress. Furthermore it is recommended not to
have clocking pins located close to a selected analog pin.
Warning: The analog input voltage level must be
within the limits stated in the Absolute Maximum
Ratings.
5.1.3 I/O Port Implementation
The hardware implementation on each I/O port depends on the settings in the DDR and OR registers
and specific feature of the I/O port such as ADC Input (see Figure 19) or true open drain. Switching
these I/O ports from one state to another should
be done in a sequence that prevents unwanted
side effects. Recommended safe transitions are illustrated in Figure 18. Other transitions are potentially risky and should be avoided, since they are
likely to present unwanted side-effects such as
spurious interrupt generation.
Figure 18. Recommended I/O State Transition Diagram
INPUT
with interrupt
INPUT
no interrupt
OUTPUT
OUTPUT
open-drain
push-pull
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ST72E121 ST72T121
I/O PORTS (Cont’d)
Figure 19. I/O Block Diagram
ALTERNATE ENABLE
ALTERNATE 1
M
OUTPUT
U
X
0
DATA BUS
COMMON ANALOG RAIL
DR
LATCH
VDD
P-BUFFER
(SEE TABLE BELOW)
ALTERNATE
ENABLE
PULL-UP
VDD
DIODE
(SEE TABLE BELOW)
PULL-UP
CONDITION
DDR
LATCH
PAD
OR
LATCH
ANALOG ENABLE
(ADC)
(SEE TABLE BELOW)
ANALOG
SWITCH
(SEE NOTE BELOW)
OR SEL
GND
DDR SEL
N-BUFFER
DR SEL
M
U
X
1
ALTERNATE
ENABLE
GND
0
ALTERNATE INPUT
CMOS
EXTERNAL
INTERRUPT
SOURCE (EIx)
POLARITY
SEL
FROM
OTHER
BITS
SCHMITT TRIGGER
Table 9. Port Mode Configuration
Configuration Mode
Floating
Pull-up
Push-pull
True Open Drain
Open Drain (logic level)
Pull-up
0
1
0
not present
0
Legend:
0present, not activated
1present and activated
Notes:
– No OR Register on some ports (see register map).
– ADC Switch on ports with analog alternate functions.
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P-buffer
0
0
1
not present
0
VDD Diode
1
1
1
not present
1
ST72E121 ST72T121
I/O PORTS (Cont’d)
Table 10. Port Configuration
Port
Pin name
PA3
Input (DDR = 0)
Output (DDR = 1)
OR = 0
OR = 1
OR = 0
OR =1
floating*
pull-up with interrupt
open-drain
push-pull
Port A
PA4:PA7
floating*
true open drain, high sink capability
Port B
PB0:PB4
floating*
pull-up with interrupt
open-drain
push-pull
Port C
PC0:PC7
floating*
pull-up
open-drain
push-pull
Port D
PD0:PD5
floating*
pull-up
open-drain
push-pull
Port E
PE0:PE1
floating*
pull-up
open-drain
push-pull
PF0:PF2
floating*
pull-up with interrupt
open-drain
push-pull
PF4, PF6, PF7
floating*
pull-up
open-drain
push-pull
Port F
* Reset state (The bits corresponding to unavailable pins are forced to 1 by hardware, this affects the reset status value).
Warning: All bits of the DDR register which correspond to unconnected I/Os must be left at their reset value. They must
not be modified by the user otherwise a spurious interrupt may be generated.
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ST72E121 ST72T121
I/O PORTS (Cont’d)
5.1.4 Register Description
5.1.4.1 Data registers
Port A Data Register (PADR)
Port B Data Register (PBDR)
Port C Data Register (PCDR)
Port D Data Register (PDDR)
Port E Data Register (PEDR)
Port F Data Register (PFDR)
Read /Write
Reset Value: 0000 0000 (00h)
5.1.4.3 Option registers
Port A Option Register (PAOR)
Port B Option Register (PBOR)
Port C Option Register (PBOR)
Port D Option Register (PBOR)
Port E Option Register (PBOR)
Port F Option Register (PFOR)
Read/Write
Reset Value: see Register Memory Map Table 3
7
D7
D6
D5
D4
D3
D2
D1
0
7
D0
O7
Bit 7:0 = D7-D0 Data Register 8 bits.
The DR register has a specific behaviour according to the selected input/output configuration. Writing the DR register is always taken in account
even if the pin is configured as an input. Reading
the DR register returns either the DR register latch
content (pin configured as output) or the digital value applied to the I/O pin (pin configured as input).
5.1.4.2 Data direction registers
Port A Data Direction Register (PADDR)
Port B Data Direction Register (PBDDR)
Port C Data Direction Register (PCDDR)
Port D Data Direction Register (PDDDR)
Port E Data Direction Register (PEDDR)
Port F Data Direction Register (PFDDR)
Read/Write
Reset Value: 0000 0000 (00h) (input mode)
7
DD7
0
DD6
DD5
DD4
DD3
DD2
DD1
DD0
Bit 7:0 = DD7-DD0 Data Direction Register 8 bits.
The DDR register gives the input/output direction
configuration of the pins. Each bits is set and
cleared by software.
0: Input mode
1: Output mode
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0
O6
O5
O4
O3
O2
O1
O0
Bit 7:0 = O7-O0 Option Register 8 bits.
The OR register allow to distinguish in input mode
if the interrupt capability or the floating configuration is selected.
In output mode it select push-pull or open-drain
capability.
Each bit is set and cleared by software.
Input mode:
0: floating input
1: input pull-up with interrupt
Output mode:
0: open-drain configuration
1: push-pull configuration
ST72E121 ST72T121
I/O PORTS (Cont’d)
Table 11. I/O Port Register Map
Address
(Hex.)
Register
Label
7
6
5
4
3
2
1
0
D7
D6
D5
D4
D3
D2
D1
D0
DD7
DD6
DD5
DD4
DD3
DD2
DD1
DD0
0000h
PADR
0001h
PADDR
0002h
PAOR
O7
O6
O5
O4
O3
O2
O1
O0
0004h
PCDR
D7
D6
D5
D4
D3
D2
D1
D0
0005h
PCDDR
DD7
DD6
DD5
DD4
DD3
DD2
DD1
DD0
0006h
PCOR
O7
O6
O5
O4
O3
O2
O1
O0
0008h
PBDR
D7
D6
D5
D4
D3
D2
D1
D0
0009h
PBDDR
DD7
DD6
DD5
DD4
DD3
DD2
DD1
DD0
000Ah
PBOR
O7
O6
O5
O4
O3
O2
O1
O0
000Ch
PEDR
D7
D6
D5
D4
D3
D2
D1
D0
000Dh
PEDDR
DD7
DD6
DD5
DD4
DD3
DD2
DD1
DD0
000Eh
PEOR
O7
O6
O5
O4
O3
O2
O1
O0
0010h
PDDR
D7
D6
D5
D4
D3
D2
D1
D0
0011h
PDDDR
DD7
DD6
DD5
DD4
DD3
DD2
DD1
DD0
0012h
PDOR
O7
O6
O5
O4
O3
O2
O1
O0
0014h
PFDR
D7
D6
D5
D4
D3
D2
D1
D0
0015h
PFDDR
DD7
DD6
DD5
DD4
DD3
DD2
DD1
DD0
0016h
PFOR
O7
O6
O5
O4
O3
O2
O1
O0
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ST72E121 ST72T121
5.2 WATCHDOG TIMER (WDG)
5.2.1 Introduction
The Watchdog timer is used to detect the occurrence of a software fault, usually generated by external interference or by unforeseen logical conditions, which causes the application program to
abandon its normal sequence. The Watchdog circuit generates an MCU reset on expiry of a programmed time period, unless the program refreshes the counter’s contents before the T6 bit becomes cleared.
5.2.2 Main Features
■ Programmable timer (64 increments of 12288
CPU cycles)
■ Programmable reset
■ Reset (if watchdog activated) after a HALT
instruction or when the T6 bit reaches zero
■
■
Hardware Watchdog selectable by option byte
Watchdog Reset indicated by status flag (in
versions with Safe Reset option only)
5.2.3 Functional Description
The counter value stored in the CR register (bits
T[6:0]), is decremented every 12,288 machine cycles, and the length of the timeout period can be
programmed by the user in 64 increments.
If the watchdog is activated (the WDGA bit is set)
and when the 7-bit timer (bits T[6:0]) rolls over
from 40h to 3Fh (T6 becomes cleared), it initiates
a reset cycle pulling low the reset pin for typically
500ns.
Figure 20. Watchdog Block Diagram
RESET
WATCHDOG CONTROL REGISTER (CR)
WDGA
T6
T5
T4
T3
T2
7-BIT DOWNCOUNTER
fCPU
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CLOCK DIVIDER
÷12288
T1
T0
ST72E121 ST72T121
WATCHDOG TIMER (Cont’d)
The application program must write in the CR register at regular intervals during normal operation to
prevent an MCU reset. The value to be stored in
the CR register must be between FFh and C0h
(see Table 12):
– The WDGA bit is set (watchdog enabled)
– The T6 bit is set to prevent generating an immediate reset
– The T[5:0] bits contain the number of increments
which represents the time delay before the
watchdog produces a reset.
Table 12.Watchdog Timing (fCPU = 8 MHz)
CR Register
initial value
WDG timeout period
(ms)
Max
FFh
98.304
Min
C0h
1.536
Notes: Following a reset, the watchdog is disabled. Once activated it cannot be disabled, except
by a reset.
The T6 bit can be used to generate a software reset (the WDGA bit is set and the T6 bit is cleared).
If the watchdog is activated, the HALT instruction
will generate a Reset.
5.2.4 Hardware Watchdog Option
If Hardware Watchdog is selected by option byte,
the watchdog is always active and the WDGA bit in
the CR is not used.
Refer to the device-specific Option Byte description.
5.2.5 Low Power Modes
Mode
WAIT
HALT
Description
No effect on Watchdog.
Immediate reset generation as soon as
the HALT instruction is executed if the
Watchdog is activated (WDGA bit is
set).
5.2.7 Register Description
CONTROL REGISTER (CR)
Read /Write
Reset Value: 0111 1111 (7Fh)
7
0
WDGA
T6
T5
T4
T3
T2
T1
T0
Bit 7 = WDGA Activation bit.
This bit is set by software and only cleared by
hardware after a reset. When WDGA = 1, the
watchdog can generate a reset.
0: Watchdog disabled
1: Watchdog enabled
Note: This bit is not used if the hardware watchdog option is enabled by option byte.
Bit 6:0 = T[6:0] 7-bit timer (MSB to LSB).
These bits contain the decremented value. A reset
is produced when it rolls over from 40h to 3Fh (T6
becomes cleared).
STATUS REGISTER (SR)
Read /Write
Reset Value*: 0000 0000 (00h)
7
-
0
-
-
-
-
-
-
WDOGF
Bit 0 = WDOGF Watchdog flag.
This bit is set by a watchdog reset and cleared by
software or a power on/off reset. This bit is useful
for distinguishing power/on off or external reset
and watchdog reset.
0: No Watchdog reset occurred
1: Watchdog reset occurred
* Only by software and power on/off reset
Note: This register is not used in versions without
LVD Reset.
5.2.6 Interrupts
None.
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ST72E121 ST72T121
Table 13. WDG Register Map
Address
(Hex.)
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32
Register
Label
7
6
5
4
3
2
1
0
2A
WDGCR
Reset Value
WDGA
0
T6
1
T5
1
T4
1
T3
1
T2
1
T1
1
T0
1
2B
WDGSR
Reset Value
0
0
0
0
0
0
0
WDOGF
0
ST72E121 ST72T121
5.3 16-BIT TIMER
5.3.1 Introduction
The timer consists of a 16-bit free-running counter
driven by a programmable prescaler.
It may be used for a variety of purposes, including
measuring the pulse lengths of up to two input signals ( input capture) or generating up to two output
waveforms (output compare and PWM ).
Pulse lengths and waveform periods can be modulated from a few microseconds to several milliseconds using the timer prescaler and the CPU
clock prescaler.
Some ST7 devices have two on-chip 16-bit timers.
They are completely independent, and do not
share any resources. They are synchronized after
a MCU reset as long as the timer clock frequencies are not modified.
This description covers one or two 16-bit timers. In
ST7 devices with two timers, register names are
prefixed with TA (Timer A) or TB (Timer B).
5.3.2 Main Features
■ Programmable prescaler: fCPU divided by 2, 4 or 8.
■ Overflow status flag and maskable interrupt
■ External clock input (must be at least 4 times
slower than the CPU clock speed) with the choice
of active edge
■ Output compare functions with:
– 2 dedicated 16-bit registers
– 2 dedicated programmable signals
– 2 dedicated status flags
– 1 dedicated maskable interrupt
■ Input capture functions with:
– 2 dedicated 16-bit registers
– 2 dedicated active edge selection signals
– 2 dedicated status flags
– 1 dedicated maskable interrupt
■ Pulse Width Modulation mode (PWM)
■ One Pulse mode
■ 5 alternate functions on I/O ports (ICAP1, ICAP2,
OCMP1, OCMP2, EXTCLK)*
5.3.3 Functional Description
5.3.3.1 Counter
The main block of the Programmable Timer is a
16-bit free running upcounter and its associated
16-bit registers. The 16-bit registers are made up
of two 8-bit registers called high & low.
Counter Register (CR):
– Counter High Register (CHR) is the most significant byte (MS Byte).
– Counter Low Register (CLR) is the least significant byte (LS Byte).
Alternate Counter Register (ACR)
– Alternate Counter High Register (ACHR) is the
most significant byte (MS Byte).
– Alternate Counter Low Register (ACLR) is the
least significant byte (LS Byte).
These two read-only 16-bit registers contain the
same value but with the difference that reading the
ACLR register does not clear the TOF bit (Timer
overflow flag), located in the Status register (SR).
(See note at the end of paragraph titled 16-bit read
sequence).
Writing in the CLR register or ACLR register resets
the free running counter to the FFFCh value.
Both counters have a reset value of FFFCh (this is
the only value which is reloaded in the 16-bit timer). The reset value of both counters is also
FFFCh in One Pulse mode and PWM mode.
The timer clock depends on the clock control bits
of the CR2 register, as illustrated in Table 14. The
value in the counter register repeats every
131072, 262144 or 524288 CPU clock cycles depending on the CC[1:0] bits.
The timer frequency can be fCPU/2, fCPU/4, fCPU/8
or an external frequency.
The Block Diagram is shown in Figure 21.
*Note: Some timer pins may not be available (not
bonded) in some ST7 devices. Refer to the device
pin out description.
When reading an input signal on a non-bonded
pin, the value will always be ‘1’.
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ST72E121 ST72T121
16-BIT TIMER (Cont’d)
Figure 21. Timer Block Diagram
ST7 INTERNAL BUS
fCPU
MCU-PERIPHERAL INTERFACE
8 low
8
8
8
low
8
high
8
low
8
high
EXEDG
8
low
high
8
high
8-bit
buffer
low
8 high
16
1/2
1/4
1/8
OUTPUT
COMPARE
REGISTER
2
OUTPUT
COMPARE
REGISTER
1
COUNTER
REGISTER
ALTERNATE
COUNTER
REGISTER
EXTCLK
pin
INPUT
CAPTURE
REGISTER
1
INPUT
CAPTURE
REGISTER
2
16
16
16
CC[1:0]
TIMER INTERNAL BUS
16 16
OVERFLOW
DETECT
CIRCUIT
OUTPUT COMPARE
CIRCUIT
6
ICF1 OCF1 TOF ICF2 OCF2 0
0
EDGE DETECT
CIRCUIT1
ICAP1
pin
EDGE DETECT
CIRCUIT2
ICAP2
pin
LATCH1
OCMP1
pin
LATCH2
OCMP2
pin
0
(Status Register) SR
ICIE OCIE TOIE FOLV2 FOLV1 OLVL2 IEDG1 OLVL1
(Control Register 1) CR1
OC1E OC2E OPM PWM
CC1
CC0 IEDG2 EXEDG
(Control Register 2) CR2
(See note)
TIMER INTERRUPT
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Note: If IC, OC and TO interrupt requests have separate vectors
then the last OR is not present (See device Interrupt Vector Table)
ST72E121 ST72T121
16-BIT TIMER (Cont’d)
16-bit Read Sequence: (from either the Counter
Register or the Alternate Counter Register).
Beginning of the sequence
At t0
Read
MS Byte
LS Byte
is buffered
Other
instructions
Read
At t0 +∆t LS Byte
Returns the buffered
LS Byte value at t0
Sequence completed
The user must read the MS Byte first, then the LS
Byte value is buffered automatically.
This buffered value remains unchanged until the
16-bit read sequence is completed, even if the
user reads the MS Byte several times.
After a complete reading sequence, if only the
CLR register or ACLR register are read, they return the LS Byte of the count value at the time of
the read.
Whatever the timer mode used (input capture, output compare, One Pulse mode or PWM mode) an
overflow occurs when the counter rolls over from
FFFFh to 0000h then:
– The TOF bit of the SR register is set.
– A timer interrupt is generated if:
– TOIE bit of the CR1 register is set and
– I bit of the CC register is cleared.
If one of these conditions is false, the interrupt remains pending to be issued as soon as they are
both true.
Clearing the overflow interrupt request is done in
two steps:
1. Reading the SR register while the TOF bit is set.
2. An access (read or write) to the CLR register.
Note: The TOF bit is not cleared by accessing the
ACLR register. The advantage of accessing the
ACLR register rather than the CLR register is that
it allows simultaneous use of the overflow function
and reading the free running counter at random
times (for example, to measure elapsed time) without the risk of clearing the TOF bit erroneously.
The timer is not affected by WAIT mode.
In HALT mode, the counter stops counting until the
mode is exited. Counting then resumes from the
previous count (MCU awakened by an interrupt) or
from the reset count (MCU awakened by a Reset).
5.3.3.2 External Clock
The external clock (where available) is selected if
CC0=1 and CC1=1 in the CR2 register.
The status of the EXEDG bit in the CR2 register
determines the type of level transition on the external clock pin EXTCLK that will trigger the free running counter.
The counter is synchronised with the falling edge
of the internal CPU clock.
A minimum of four falling edges of the CPU clock
must occur between two consecutive active edges
of the external clock; thus the external clock frequency must be less than a quarter of the CPU
clock frequency.
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ST72E121 ST72T121
16-BIT TIMER (Cont’d)
Figure 22. Counter Timing Diagram, internal clock divided by 2
CPU CLOCK
INTERNAL RESET
TIMER CLOCK
FFFD FFFE FFFF 0000
COUNTER REGISTER
0001
0002
0003
TIMER OVERFLOW FLAG (TOF)
Figure 23. Counter Timing Diagram, internal clock divided by 4
CPU CLOCK
INTERNAL RESET
TIMER CLOCK
COUNTER REGISTER
FFFC
FFFD
0000
0001
TIMER OVERFLOW FLAG (TOF)
Figure 24. Counter Timing Diagram, internal clock divided by 8
CPU CLOCK
INTERNAL RESET
TIMER CLOCK
COUNTER REGISTER
FFFC
FFFD
0000
TIMER OVERFLOW FLAG (TOF)
Note: The MCU is in reset state when the internal reset signal is high. When it is low, the MCU is running.
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ST72E121 ST72T121
16-BIT TIMER (Cont’d)
5.3.3.3 Input Capture
In this section, the index, i, may be 1 or 2 because
there are 2 input capture functions in the 16-bit
timer.
The two input capture 16-bit registers (IC1R and
IC2R) are used to latch the value of the free running counter after a transition is detected by the
ICAP i pin (see figure 5).
ICiR
MS Byte
ICiHR
LS Byte
ICiLR
The ICiR register is a read-only register.
The active transition is software programmable
through the IEDGi bit of Control Registers (CRi).
Timing resolution is one count of the free running
counter: (fCPU/CC[1:0]).
Procedure:
To use the input capture function, select the following in the CR2 register:
– Select the timer clock (CC[1:0]) (see Table 14).
– Select the edge of the active transition on the
ICAP2 pin with the IEDG2 bit (the ICAP2 pin
must be configured as a floating input).
And select the following in the CR1 register:
– Set the ICIE bit to generate an interrupt after an
input capture coming from either the ICAP1 pin
or the ICAP2 pin
– Select the edge of the active transition on the
ICAP1 pin with the IEDG1 bit (the ICAP1pin must
be configured as a floating input).
When an input capture occurs:
– The ICFi bit is set.
– The ICiR register contains the value of the free
running counter on the active transition on the
ICAPi pin (see Figure 26).
– A timer interrupt is generated if the ICIE bit is set
and the I bit is cleared in the CC register. Otherwise, the interrupt remains pending until both
conditions become true.
Clearing the Input Capture interrupt request (i.e.
clearing the ICFi bit) is done in two steps:
1. Reading the SR register while the ICFi bit is set.
2. An access (read or write) to the ICiLR register.
Notes:
1. After reading the ICiHR register, the transfer of
input capture data is inhibited and ICFi will
never be set until the ICiLR register is also
read.
2. The ICiR register contains the free running
counter value which corresponds to the most
recent input capture.
3. The 2 input capture functions can be used
together even if the timer also uses the 2 output
compare functions.
4. In One Pulse mode and PWM mode only the
input capture 2 function can be used.
5. The alternate inputs (ICAP1 & ICAP2) are
always directly connected to the timer. So any
transitions on these pins activate the input capture function.
Moreover if one of the ICAPi pin is configured
as an input and the second one as an output,
an interrupt can be generated if the user toggles the output pin and if the ICIE bit is set.
This can be avoided if the input capture function i is disabled by reading the IC iHR (see note
1).
6. The TOF bit can be used with an interrupt in
order to measure events that exceed the timer
range (FFFFh).
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ST72E121 ST72T121
16-BIT TIMER (Cont’d)
Figure 25. Input Capture Block Diagram
ICAP1
pin
ICAP2
pin
(Control Register 1) CR1
EDGE DETECT
CIRCUIT2
EDGE DETECT
CIRCUIT1
ICIE
IEDG1
(Status Register) SR
IC1R Register
IC2R Register
ICF1
ICF2
0
16-BIT FREE RUNNING
CC1
CC0
COUNTER
Figure 26. Input Capture Timing Diagram
TIMER CLOCK
FF01
FF02
FF03
ICAPi PIN
ICAPi FLAG
ICAPi REGISTER
Note: Active edge is rising edge.
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0
(Control Register 2) CR2
16-BIT
COUNTER REGISTER
0
FF03
IEDG2
ST72E121 ST72T121
16-BIT TIMER (Cont’d)
5.3.3.4 Output Compare
In this section, the index, i, may be 1 or 2 because
there are 2 output compare functions in the 16-bit
timer.
This function can be used to control an output
waveform or indicate when a period of time has
elapsed.
When a match is found between the Output Compare register and the free running counter, the output compare function:
– Assigns pins with a programmable value if the
OCIE bit is set
– Sets a flag in the status register
– Generates an interrupt if enabled
Two 16-bit registers Output Compare Register 1
(OC1R) and Output Compare Register 2 (OC2R)
contain the value to be compared to the counter
register each timer clock cycle.
OCiR
MS Byte
OCiHR
LS Byte
OCiLR
These registers are readable and writable and are
not affected by the timer hardware. A reset event
changes the OCiR value to 8000h.
Timing resolution is one count of the free running
counter: (fCPU/CC[1:0]).
Procedure:
To use the output compare function, select the following in the CR2 register:
– Set the OCiE bit if an output is needed then the
OCMPi pin is dedicated to the output compare i
signal.
– Select the timer clock (CC[1:0]) (see Table 14).
And select the following in the CR1 register:
– Select the OLVLi bit to applied to the OCMP i pins
after the match occurs.
– Set the OCIE bit to generate an interrupt if it is
needed.
When a match is found between OCRi register
and CR register:
– OCFi bit is set.
– The OCMP i pin takes OLVLi bit value (OCMPi
pin latch is forced low during reset).
– A timer interrupt is generated if the OCIE bit is
set in the CR2 register and the I bit is cleared in
the CC register (CC).
The OCiR register value required for a specific timing application can be calculated using the following formula:
∆ OCiR =
∆t * fCPU
PRESC
Where:
∆t
= Output compare period (in seconds)
fCPU
= CPU clock frequency (in hertz)
PRESC = Timer prescaler factor (2, 4 or 8 depending on CC[1:0] bits, see Table 14)
If the timer clock is an external clock, the formula
is:
∆ OCiR = ∆t * fEXT
Where:
∆t
= Output compare period (in seconds)
= External timer clock frequency (in hertz)
fEXT
Clearing the output compare interrupt request (i.e.
clearing the OCFi bit) is done by:
1. Reading the SR register while the OCFi bit is
set.
2. An access (read or write) to the OCiLR register.
The following procedure is recommended to prevent the OCFi bit from being set between the time
it is read and the write to the OCiR register:
– Write to the OCiHR register (further compares
are inhibited).
– Read the SR register (first step of the clearance
of the OCFi bit, which may be already set).
– Write to the OCiLR register (enables the output
compare function and clears the OCFi bit).
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ST72E121 ST72T121
16-BIT TIMER (Cont’d)
Notes:
1. After a processor write cycle to the OCiHR register, the output compare function is inhibited
until the OCiLR register is also written.
2. If the OCiE bit is not set, the OCMPi pin is a
general I/O port and the OLVLi bit will not
appear when a match is found but an interrupt
could be generated if the OCIE bit is set.
3. When the timer clock is fCPU/2, OCFi and
OCMPi are set while the counter value equals
the OCiR register value (see Figure 28, on
page 41). This behaviour is the same in OPM
or PWM mode.
When the timer clock is fCPU/4, fCPU/8 or in
external clock mode, OCFi and OCMPi are set
while the counter value equals the OCiR register value plus 1 (see Figure 29, on page 41).
4. The output compare functions can be used both
for generating external events on the OCMPi
pins even if the input capture mode is also
used.
5. The value in the 16-bit OCiR register and the
OLVi bit should be changed after each successful comparison in order to control an output
waveform or establish a new elapsed timeout.
Forced Compare Output capability
When the FOLVi bit is set by software, the OLVLi
bit is copied to the OCMPi pin. The OLVi bit has to
be toggled in order to toggle the OCMPi pin when
it is enabled (OCiE bit=1). The OCFi bit is then not
set by hardware, and thus no interrupt request is
generated.
FOLVLi bits have no effect in either One-Pulse
mode or PWM mode.
Figure 27. Output Compare Block Diagram
16 BIT FREE RUNNING
COUNTER
OC1E OC2E
CC1
CC0
(Control Register 2) CR2
16-bit
(Control Register 1) CR1
OUTPUT COMPARE
CIRCUIT
16-bit
OCIE
FOLV2 FOLV1 OLVL2
OLVL1
16-bit
Latch
2
OC1R Register
OCF1
OCF2
0
0
0
OC2R Register
(Status Register) SR
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40
Latch
1
OCMP1
Pin
OCMP2
Pin
ST72E121 ST72T121
16-BIT TIMER (Cont’d)
Figure 28. Output Compare Timing Diagram, fTIMER =fCPU/2
INTERNAL CPU CLOCK
TIMER CLOCK
COUNTER REGISTER
2ECF 2ED0
2ED1 2ED2 2ED3 2ED4
OUTPUT COMPARE REGISTER i (OCRi)
2ED3
OUTPUT COMPARE FLAG i (OCFi)
OCMPi PIN (OLVLi=1)
Figure 29. Output Compare Timing Diagram, fTIMER =fCPU/4
INTERNAL CPU CLOCK
TIMER CLOCK
COUNTER REGISTER
OUTPUT COMPARE REGISTER i (OCRi)
2ECF 2ED0
2ED1 2ED2 2ED3 2ED4
2ED3
COMPARE REGISTER i LATCH
OUTPUT COMPARE FLAG i (OCFi)
OCMPi PIN (OLVLi=1)
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ST72E121 ST72T121
16-BIT TIMER (Cont’d)
5.3.3.5 One Pulse Mode
One Pulse mode enables the generation of a
pulse when an external event occurs. This mode is
selected via the OPM bit in the CR2 register.
The One Pulse mode uses the Input Capture1
function and the Output Compare1 function.
Procedure:
To use One Pulse mode:
1. Load the OC1R register with the value corresponding to the length of the pulse (see the formula in the opposite column).
2. Select the following in the CR1 register:
– Using the OLVL1 bit, select the level to be applied to the OCMP1 pin after the pulse.
– Using the OLVL2 bit, select the level to be applied to the OCMP1 pin during the pulse.
– Select the edge of the active transition on the
ICAP1 pin with the IEDG1 bit (the ICAP1 pin
must be configured as floating input).
3. Select the following in the CR2 register:
– Set the OC1E bit, the OCMP1 pin is then dedicated to the Output Compare 1 function.
– Set the OPM bit.
– Select the timer clock CC[1:0] (see Table 14).
One Pulse mode cycle
When
event occurs
on ICAP1
OCMP1 = OLVL2
Counter is reset
to FFFCh
ICF1 bit is set
When
Counter
= OC1R
OCMP1 = OLVL1
Then, on a valid event on the ICAP1 pin, the counter is initialized to FFFCh and the OLVL2 bit is
loaded on the OCMP1 pin, the ICF1 bit is set and
the value FFFDh is loaded in the IC1R register.
Because the ICF1 bit is set when an active edge
occurs, an interrupt can be generated if the ICIE
bit is set.
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Clearing the Input Capture interrupt request (i.e.
clearing the ICFi bit) is done in two steps:
1. Reading the SR register while the ICFi bit is set.
2. An access (read or write) to the ICiLR register.
The OC1R register value required for a specific
timing application can be calculated using the following formula:
OCiR Value =
t * fCPU
-5
PRESC
Where:
t
= Pulse period (in seconds)
fCPU = CPU clock frequency (in hertz)
PRESC = Timer prescaler factor (2, 4 or 8 depending on the CC[1:0] bits, see Table 14)
If the timer clock is an external clock the formula is:
OCiR = t * fEXT -5
Where:
t
= Pulse period (in seconds)
fEXT
= External timer clock frequency (in hertz)
When the value of the counter is equal to the value
of the contents of the OC1R register, the OLVL1
bit is output on the OCMP1 pin (see Figure 30).
Notes:
1. The OCF1 bit cannot be set by hardware in
One Pulse mode but the OCF2 bit can generate
an Output Compare interrupt.
2. When the Pulse Width Modulation (PWM) and
One Pulse mode (OPM) bits are both set, the
PWM mode is the only active one.
3. If OLVL1=OLVL2 a continuous signal will be
seen on the OCMP1 pin.
4. The ICAP1 pin can not be used to perform input
capture. The ICAP2 pin can be used to perform
input capture (ICF2 can be set and IC2R can be
loaded) but the user must take care that the
counter is reset each time a valid edge occurs
on the ICAP1 pin and ICF1 can also generates
interrupt if ICIE is set.
5. When One Pulse mode is used OC1R is dedicated to this mode. Nevertheless OC2R and
OCF2 can be used to indicate that a period of
time has elapsed but cannot generate an output
waveform because the OLVL2 level is dedicated to One Pulse mode.
ST72E121 ST72T121
16-BIT TIMER (Cont’d)
Figure 30. One Pulse Mode Timing Example
COUNTER
FFFC FFFD FFFE
2ED0 2ED1 2ED2
FFFC FFFD
2ED3
ICAP1
OLVL2
OCMP1
OLVL1
OLVL2
compare1
Note: IEDG1=1, OC1R=2ED0h, OLVL1=0, OLVL2=1
Figure 31. Pulse Width Modulation Mode Timing Example
COUNTER 34E2 FFFC FFFD FFFE
2ED0 2ED1 2ED2
OLVL2
OCMP1
compare2
OLVL1
compare1
34E2
FFFC
OLVL2
compare2
Note: OC1R=2ED0h, OC2R=34E2, OLVL1=0, OLVL2= 1
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ST72E121 ST72T121
16-BIT TIMER (Cont’d)
5.3.3.6 Pulse Width Modulation Mode
Pulse Width Modulation (PWM) mode enables the
generation of a signal with a frequency and pulse
length determined by the value of the OC1R and
OC2R registers.
The Pulse Width Modulation mode uses the complete Output Compare 1 function plus the OC2R
register, and so these functions cannot be used
when the PWM mode is activated.
Procedure
To use Pulse Width Modulation mode:
1. Load the OC2R register with the value corresponding to the period of the signal using the
formula in the opposite column.
2. Load the OC1R register with the value corresponding to the period of the pulse if OLVL1=0
and OLVL2=1, using the formula in the opposite column.
3. Select the following in the CR1 register:
– Using the OLVL1 bit, select the level to be applied to the OCMP1 pin after a successful
comparison with OC1R register.
– Using the OLVL2 bit, select the level to be applied to the OCMP1 pin after a successful
comparison with OC2R register.
4. Select the following in the CR2 register:
– Set OC1E bit: the OCMP1 pin is then dedicated to the output compare 1 function.
– Set the PWM bit.
– Select the timer clock (CC[1:0]) (see Table
14).
If OLVL1=1 and OLVL2=0, the length of the positive pulse is the difference between the OC2R and
OC1R registers.
If OLVL1=OLVL2 a continuous signal will be seen
on the OCMP1 pin.
Pulse Width Modulation cycle
When
Counter
= OC1R
When
Counter
= OC2R
OCMP1 = OLVL1
OCMP1 = OLVL2
Counter is reset
to FFFCh
ICF1 bit is set
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The OCiR register value required for a specific timing application can be calculated using the following formula:
OCiR Value =
t * fCPU
-5
PRESC
Where:
t
= Signal or pulse period (in seconds)
fCPU = CPU clock frequency (in hertz)
PRESC = Timer prescaler factor (2, 4 or 8 depending on CC[1:0] bits, see Table 14)
If the timer clock is an external clock the formula is:
OCiR = t * fEXT -5
Where:
t
= Signal or pulse period (in seconds)
fEXT
= External timer clock frequency (in hertz)
The Output Compare 2 event causes the counter
to be initialized to FFFCh (See Figure 31)
Notes:
1. After a write instruction to the OCiHR register,
the output compare function is inhibited until the
OCiLR register is also written.
2. The OCF1 and OCF2 bits cannot be set by
hardware in PWM mode, therefore the Output
Compare interrupt is inhibited.
3. The ICF1 bit is set by hardware when the counter reaches the OC2R value and can produce a
timer interrupt if the ICIE bit is set and the I bit is
cleared.
4. In PWM mode the ICAP1 pin can not be used
to perform input capture because it is disconnected from the timer. The ICAP2 pin can be
used to perform input capture (ICF2 can be set
and IC2R can be loaded) but the user must
take care that the counter is reset after each
period and ICF1 can also generate an interrupt
if ICIE is set.
5. When the Pulse Width Modulation (PWM) and
One Pulse mode (OPM) bits are both set, the
PWM mode is the only active one.
ST72E121 ST72T121
16-BIT TIMER (Cont’d)
5.3.4 Low Power Modes
Mode
WAIT
HALT
Description
No effect on 16-bit Timer.
Timer interrupts cause the device to exit from WAIT mode.
16-bit Timer registers are frozen.
In HALT mode, the counter stops counting until Halt mode is exited. Counting resumes from the previous
count when the MCU is woken up by an interrupt with “exit from HALT mode” capability or from the counter
reset value when the MCU is woken up by a RESET.
If an input capture event occurs on the ICAPi pin, the input capture detection circuitry is armed. Consequently, when the MCU is woken up by an interrupt with “exit from HALT mode” capability, the ICFi bit is set, and
the counter value present when exiting from HALT mode is captured into the ICiR register.
5.3.5 Interrupts
Event
Flag
Interrupt Event
Input Capture 1 event/Counter reset in PWM mode
Input Capture 2 event
Output Compare 1 event (not available in PWM mode)
Output Compare 2 event (not available in PWM mode)
Timer Overflow event
ICF1
ICF2
OCF1
OCF2
TOF
Enable
Control
Bit
ICIE
OCIE
TOIE
Exit
from
Wait
Yes
Yes
Yes
Yes
Yes
Exit
from
Halt
No
No
No
No
No
Note: The 16-bit Timer interrupt events are connected to the same interrupt vector (see Interrupts chapter). These events generate an interrupt if the corresponding Enable Control Bit is set and the interrupt
mask in the CC register is reset (RIM instruction).
5.3.6 Summary of Timer modes
MODES
Input Capture (1 and/or 2)
Output Compare (1 and/or 2)
One Pulse mode
PWM Mode
Input Capture 1
Yes
Yes
No
No
AVAILABLE RESOURCES
Input Capture 2
Output Compare 1 Output Compare 2
Yes
Yes
Yes
Yes
Yes
Yes
1)
No
Partially 2)
Not Recommended
3)
Not Recommended
No
No
1)
See note 4 in Section 5.3.3.5 One Pulse Mode
See note 5 in Section 5.3.3.5 One Pulse Mode
3)
See note 4 in Section 5.3.3.6 Pulse Width Modulation Mode
2)
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ST72E121 ST72T121
16-BIT TIMER (Cont’d)
5.3.7 Register Description
Each Timer is associated with three control and
status registers, and with six pairs of data registers
(16-bit values) relating to the two input captures,
the two output compares, the counter and the alternate counter.
CONTROL REGISTER 1 (CR1)
Read/Write
Reset Value: 0000 0000 (00h)
7
0
Bit 4 = FOLV2 Forced Output Compare 2.
This bit is set and cleared by software.
0: No effect on the OCMP2 pin.
1: Forces the OLVL2 bit to be copied to the
OCMP2 pin, if the OC2E bit is set and even if
there is no successful comparison.
Bit 3 = FOLV1 Forced Output Compare 1.
This bit is set and cleared by software.
0: No effect on the OCMP1 pin.
1: Forces OLVL1 to be copied to the OCMP1 pin, if
the OC1E bit is set and even if there is no successful comparison.
ICIE OCIE TOIE FOLV2 FOLV1 OLVL2 IEDG1 OLVL1
Bit 7 = ICIE Input Capture Interrupt Enable.
0: Interrupt is inhibited.
1: A timer interrupt is generated whenever the
ICF1 or ICF2 bit of the SR register is set.
Bit 6 = OCIE Output Compare Interrupt Enable.
0: Interrupt is inhibited.
1: A timer interrupt is generated whenever the
OCF1 or OCF2 bit of the SR register is set.
Bit 5 = TOIE Timer Overflow Interrupt Enable.
0: Interrupt is inhibited.
1: A timer interrupt is enabled whenever the TOF
bit of the SR register is set.
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46
Bit 2 = OLVL2 Output Level 2.
This bit is copied to the OCMP2 pin whenever a
successful comparison occurs with the OC2R register and OCxE is set in the CR2 register. This value is copied to the OCMP1 pin in One Pulse mode
and Pulse Width Modulation mode.
Bit 1 = IEDG1 Input Edge 1.
This bit determines which type of level transition
on the ICAP1 pin will trigger the capture.
0: A falling edge triggers the capture.
1: A rising edge triggers the capture.
Bit 0 = OLVL1 Output Level 1.
The OLVL1 bit is copied to the OCMP1 pin whenever a successful comparison occurs with the
OC1R register and the OC1E bit is set in the CR2
register.
ST72E121 ST72T121
16-BIT TIMER (Cont’d)
CONTROL REGISTER 2 (CR2)
Read/Write
Reset Value: 0000 0000 (00h)
7
0
OC1E OC2E OPM PWM CC1 CC0 IEDG2 EXEDG
Bit 7 = OC1E Output Compare 1 Pin Enable.
This bit is used only to output the signal from the
timer on the OCMP1 pin (OLV1 in Output Compare mode, both OLV1 and OLV2 in PWM and
one-pulse mode). Whatever the value of the OC1E
bit, the internal Output Compare 1 function of the
timer remains active.
0: OCMP1 pin alternate function disabled (I/O pin
free for general-purpose I/O).
1: OCMP1 pin alternate function enabled.
Bit 6 = OC2E Output Compare 2 Pin Enable.
This bit is used only to output the signal from the
timer on the OCMP2 pin (OLV2 in Output Compare mode). Whatever the value of the OC2E bit,
the internal Output Compare 2 function of the timer
remains active.
0: OCMP2 pin alternate function disabled (I/O pin
free for general-purpose I/O).
1: OCMP2 pin alternate function enabled.
Bit 5 = OPM One Pulse mode.
0: One Pulse mode is not active.
1: One Pulse mode is active, the ICAP1 pin can be
used to trigger one pulse on the OCMP1 pin; the
active transition is given by the IEDG1 bit. The
length of the generated pulse depends on the
contents of the OC1R register.
Bit 4 = PWM Pulse Width Modulation.
0: PWM mode is not active.
1: PWM mode is active, the OCMP1 pin outputs a
programmable cyclic signal; the length of the
pulse depends on the value of OC1R register;
the period depends on the value of OC2R register.
Bits 3:2 = CC[1:0] Clock Control.
The timer clock mode depends on these bits:
Table 14. Clock Control Bits
Timer Clock
fCPU / 4
fCPU / 2
fCPU / 8
External Clock (where
available)
CC1
0
0
1
CC0
0
1
0
1
1
Note: If the external clock pin is not available, programming the external clock configuration stops
the counter.
Bit 1 = IEDG2 Input Edge 2.
This bit determines which type of level transition
on the ICAP2 pin will trigger the capture.
0: A falling edge triggers the capture.
1: A rising edge triggers the capture.
Bit 0 = EXEDG External Clock Edge.
This bit determines which type of level transition
on the external clock pin (EXTCLK) will trigger the
counter register.
0: A falling edge triggers the counter register.
1: A rising edge triggers the counter register.
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ST72E121 ST72T121
16-BIT TIMER (Cont’d)
STATUS REGISTER (SR)
Read Only
Reset Value: 0000 0000 (00h)
The three least significant bits are not used.
7
ICF1
0
OCF1
TOF
ICF2
OCF2
0
0
0
Bit 7 = ICF1 Input Capture Flag 1.
0: No input capture (reset value).
1: An input capture has occurred on the ICAP1 pin
or the counter has reached the OC2R value in
PWM mode. To clear this bit, first read the SR
register, then read or write the low byte of the
IC1R (IC1LR) register.
Bit 6 = OCF1 Output Compare Flag 1.
0: No match (reset value).
1: The content of the free running counter matches
the content of the OC1R register. To clear this
bit, first read the SR register, then read or write
the low byte of the OC1R (OC1LR) register.
Bit 5 = TOF Timer Overflow Flag.
0: No timer overflow (reset value).
1: The free running counter has rolled over from
FFFFh to 0000h. To clear this bit, first read the
SR register, then read or write the low byte of
the CR (CLR) register.
Note: Reading or writing the ACLR register does
not clear TOF.
Bit 4 = ICF2 Input Capture Flag 2.
0: No input capture (reset value).
1: An input capture has occurred on the ICAP2
pin. To clear this bit, first read the SR register,
then read or write the low byte of the IC2R
(IC2LR) register.
Bit 3 = OCF2 Output Compare Flag 2.
0: No match (reset value).
1: The content of the free running counter matches
the content of the OC2R register. To clear this
bit, first read the SR register, then read or write
the low byte of the OC2R (OC2LR) register.
Bit 2-0 = Reserved, forced by hardware to 0.
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INPUT CAPTURE 1 HIGH REGISTER (IC1HR)
Read Only
Reset Value: Undefined
This is an 8-bit read only register that contains the
high part of the counter value (transferred by the
input capture 1 event).
7
0
MSB
LSB
INPUT CAPTURE 1 LOW REGISTER (IC1LR)
Read Only
Reset Value: Undefined
This is an 8-bit read only register that contains the
low part of the counter value (transferred by the input capture 1 event).
7
0
MSB
LSB
OUTPUT COMPARE 1 HIGH REGISTER
(OC1HR)
Read/Write
Reset Value: 1000 0000 (80h)
This is an 8-bit register that contains the high part
of the value to be compared to the CHR register.
7
0
MSB
LSB
OUTPUT COMPARE 1 LOW REGISTER
(OC1LR)
Read/Write
Reset Value: 0000 0000 (00h)
This is an 8-bit register that contains the low part of
the value to be compared to the CLR register.
7
0
MSB
LSB
ST72E121 ST72T121
16-BIT TIMER (Cont’d)
OUTPUT COMPARE 2 HIGH REGISTER
(OC2HR)
Read/Write
Reset Value: 1000 0000 (80h)
This is an 8-bit register that contains the high part
of the value to be compared to the CHR register.
ALTERNATE COUNTER HIGH REGISTER
(ACHR)
Read Only
Reset Value: 1111 1111 (FFh)
This is an 8-bit register that contains the high part
of the counter value.
7
0
7
0
MSB
LSB
MSB
LSB
OUTPUT COMPARE 2 LOW REGISTER
(OC2LR)
Read/Write
Reset Value: 0000 0000 (00h)
This is an 8-bit register that contains the low part of
the value to be compared to the CLR register.
7
0
MSB
LSB
COUNTER HIGH REGISTER (CHR)
Read Only
Reset Value: 1111 1111 (FFh)
This is an 8-bit register that contains the high part
of the counter value.
7
0
MSB
LSB
COUNTER LOW REGISTER (CLR)
Read Only
Reset Value: 1111 1100 (FCh)
This is an 8-bit register that contains the low part of
the counter value. A write to this register resets the
counter. An access to this register after accessing
the SR register clears the TOF bit.
7
0
MSB
LSB
ALTERNATE COUNTER LOW REGISTER
(ACLR)
Read Only
Reset Value: 1111 1100 (FCh)
This is an 8-bit register that contains the low part of
the counter value. A write to this register resets the
counter. An access to this register after an access
to SR register does not clear the TOF bit in SR
register.
7
0
MSB
LSB
INPUT CAPTURE 2 HIGH REGISTER (IC2HR)
Read Only
Reset Value: Undefined
This is an 8-bit read only register that contains the
high part of the counter value (transferred by the
Input Capture 2 event).
7
0
MSB
LSB
INPUT CAPTURE 2 LOW REGISTER (IC2LR)
Read Only
Reset Value: Undefined
This is an 8-bit read only register that contains the
low part of the counter value (transferred by the Input Capture 2 event).
7
0
MSB
LSB
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ST72E121 ST72T121
16-BIT TIMER (Cont’d)
Table 15. 16-Bit Timer Register Map and Reset Values
Address
(Hex.)
Register
Name
TimerA: 32 CR1
TimerB: 42 Reset Value
TimerA: 31 CR2
TimerB: 41 Reset Value
TimerA: 33 SR
TimerB: 43 Reset Value
TimerA: 34 IC1HR
TimerB: 44 Reset Value
TimerA: 35 IC1LR
TimerB: 45 Reset Value
TimerA: 36 OC1HR
TimerB: 46 Reset Value
TimerA: 37 OC1LR
TimerB: 47 Reset Value
TimerA: 3E OC2HR
TimerB: 4E Reset Value
TimerA: 3F OC2LR
TimerB: 4F Reset Value
TimerA: 38 CHR
TimerB: 48 Reset Value
TimerA: 39 CLR
TimerB: 49 Reset Value
TimerA: 3A ACHR
TimerB: 4A Reset Value
TimerA: 3B ACLR
TimerB: 4B Reset Value
TimerA: 3C IC2HR
TimerB: 4C Reset Value
TimerA: 3D IC2LR
TimerB: 4D Reset Value
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7
6
5
4
3
2
1
0
ICIE
OCIE
TOIE
FOLV2
FOLV1
OLVL2
IEDG1
OLVL1
0
0
0
0
0
0
0
0
OC1E
OC2E
OPM
PWM
CC1
CC0
IEDG2
EXEDG
0
0
0
0
0
0
0
0
ICF1
OCF1
TOF
ICF2
OCF2
-
-
-
0
0
0
0
0
0
0
0
MSB
-
-
-
-
-
-
-
LSB
-
MSB
-
-
-
-
-
-
-
LSB
-
MSB
1
0
0
0
0
0
0
LSB
0
MSB
0
0
0
0
0
0
0
LSB
0
MSB
1
0
0
0
0
0
0
LSB
0
MSB
0
0
0
0
0
0
0
LSB
0
MSB
1
1
1
1
1
1
1
LSB
1
MSB
1
1
1
1
1
1
0
LSB
0
MSB
1
1
1
1
1
1
1
LSB
1
MSB
1
1
1
1
1
1
0
LSB
0
MSB
-
-
-
-
-
-
-
LSB
-
MSB
-
-
-
-
-
-
-
LSB
-
ST72E121 ST72T121
5.4 SERIAL COMMUNICATIONS INTERFACE (SCI)
5.4.1 Introduction
The Serial Communications Interface (SCI) offers
a flexible means of full-duplex data exchange with
external equipment requiring an industry standard
NRZ asynchronous serial data format. The SCI offers a very wide range of baud rates using two
baud rate generator systems.
5.4.2 Main Features
■ Full duplex, asynchronous communications
■ NRZ standard format (Mark/Space)
■ Dual baud rate generator systems
■ Independently
programmable transmit and
receive baud rates up to 250K baud.
■ Programmable data word length (8 or 9 bits)
■ Receive buffer full, Transmit buffer empty and
End of Transmission flags
■ Two receiver wake-up modes:
– Address bit (MSB)
– Idle line
■ Muting function for multiprocessor configurations
■ Separate enable bits for Transmitter and
Receiver
■ Three error detection flags:
– Overrun error
– Noise error
– Frame error
■ Five interrupt sources with flags:
– Transmit data register empty
– Transmission complete
– Receive data register full
– Idle line received
– Overrun error detected
5.4.3 General Description
The interface is externally connected to another
device by two pins (see Figure 33):
– TDO: Transmit Data Output. When the transmitter is disabled, the output pin returns to its I/O
port configuration. When the transmitter is enabled and nothing is to be transmitted, the TDO
pin is at high level.
– RDI: Receive Data Input is the serial data input.
Oversampling techniques are used for data recovery by discriminating between valid incoming
data and noise.
Through this pins, serial data is transmitted and received as frames comprising:
– An Idle Line prior to transmission or reception
– A start bit
– A data word (8 or 9 bits) least significant bit first
– A Stop bit indicating that the frame is complete.
This interface uses two types of baud rate generator:
– A conventional type for commonly-used baud
rates,
– An extended type with a prescaler offering a very
wide range of baud rates even with non-standard
oscillator frequencies.
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ST72E121 ST72T121
SERIAL COMMUNICATIONS INTERFACE (Cont’d)
Figure 32. SCI Block Diagram
Write
Read
(DATA REGISTER) DR
Received Data Register (RDR)
Transmit Data Register (TDR)
TDO
Received Shift Register
Transmit Shift Register
RDI
CR1
R8
TRANSMIT
WAKE
UP
CONTROL
UNIT
T8
-
M
WAKE
-
-
-
RECEIVER
CLOCK
RECEIVER
CONTROL
SR
CR2
TIE TCIE RIE
ILIE
TE
RE RWU SBK
TDRE TC RDRF IDLE OR
NF
FE
SCI
INTERRUPT
CONTROL
TRANSMITTER
CLOCK
TRANSMITTER RATE
fCPU
CONTROL
/16
/2
/PR
BRR
SCP1 SCP0 SCT2 SCT1 SCT0 SCR2 SCR1SCR0
RECEIVER RATE
CONTROL
CONVENTIONAL BAUD RATE GENERATOR
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-
ST72E121 ST72T121
SERIAL COMMUNICATIONS INTERFACE (Cont’d)
5.4.4 Functional Description
The block diagram of the Serial Control Interface,
is shown in Figure 32. It contains 6 dedicated registers:
– Two control registers (CR1 & CR2)
– A status register (SR)
– A baud rate register (BRR)
– An extended prescaler receiver register (ERPR)
– An extended prescaler transmitter register (ETPR)
Refer to the register descriptions in Section
5.4.7for the definitions of each bit.
5.4.4.1 Serial Data Format
Word length may be selected as being either 8 or 9
bits by programming the M bit in the CR1 register
(see Figure 32).
The TDO pin is in low state during the start bit.
The TDO pin is in high state during the stop bit.
An Idle character is interpreted as an entire frame
of “1”s followed by the start bit of the next frame
which contains data.
A Break character is interpreted on receiving “0”s
for some multiple of the frame period. At the end of
the last break frame the transmitter inserts an extra “1” bit to acknowledge the start bit.
Transmission and reception are driven by their
own baud rate generator.
Figure 33. Word length programming
9-bit Word length (M bit is set)
Possible
Parity
Bit
Data Frame
Start
Bit
Bit0
Bit2
Bit1
Bit3
Bit4
Bit5
Bit6
Start
Bit
Break Frame
Extra
’1’
Possible
Parity
Bit
Data Frame
Bit0
Bit8
Next
Stop Start
Bit
Bit
Idle Frame
8-bit Word length (M bit is reset)
Start
Bit
Bit7
Next Data Frame
Bit1
Bit2
Bit3
Bit4
Bit5
Bit6
Bit7
Start
Bit
Next Data Frame
Stop
Bit
Next
Start
Bit
Idle Frame
Start
Bit
Break Frame
Extra Start
Bit
’1’
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ST72E121 ST72T121
SERIAL COMMUNICATIONS INTERFACE (Cont’d)
5.4.4.2 Transmitter
The transmitter can send data words of either 8 or
9 bits depending on the M bit status. When the M
bit is set, word length is 9 bits and the 9th bit (the
MSB) has to be stored in the T8 bit in the CR1 register.
Character Transmission
During an SCI transmission, data shifts out least
significant bit first on the TDO pin. In this mode,
the DR register consists of a buffer (TDR) between
the internal bus and the transmit shift register (see
Figure 32).
Procedure
– Select the M bit to define the word length.
– Select the desired baud rate using the BRR and
the ETPR registers.
– Set the TE bit to assign the TDO pin to the alternate function and to send a idle frame as first
transmission.
– Access the SR register and write the data to
send in the DR register (this sequence clears the
TDRE bit). Repeat this sequence for each data to
be transmitted.
Clearing the TDRE bit is always performed by the
following software sequence:
1. An access to the SR register
2. A write to the DR register
The TDRE bit is set by hardware and it indicates:
– The TDR register is empty.
– The data transfer is beginning.
– The next data can be written in the DR register
without overwriting the previous data.
This flag generates an interrupt if the TIE bit is set
and the I bit is cleared in the CCR register.
When a transmission is taking place, a write instruction to the DR register stores the data in the
TDR register and which is copied in the shift register at the end of the current transmission.
When no transmission is taking place, a write instruction to the DR register places the data directly
in the shift register, the data transmission starts,
and the TDRE bit is immediately set.
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When a frame transmission is complete (after the
stop bit or after the break frame) the TC bit is set
and an interrupt is generated if the TCIE is set and
the I bit is cleared in the CCR register.
Clearing the TC bit is performed by the following
software sequence:
1. An access to the SR register
2. A write to the DR register
Note: The TDRE and TC bits are cleared by the
same software sequence.
Break Characters
Setting the SBK bit loads the shift register with a
break character. The break frame length depends
on the M bit (see Figure 33).
As long as the SBK bit is set, the SCI send break
frames to the TDO pin. After clearing this bit by
software the SCI insert a logic 1 bit at the end of
the last break frame to guarantee the recognition
of the start bit of the next frame.
Idle Characters
Setting the TE bit drives the SCI to send an idle
frame before the first data frame.
Clearing and then setting the TE bit during a transmission sends an idle frame after the current word.
Note: Resetting and setting the TE bit causes the
data in the TDR register to be lost. Therefore the
best time to toggle the TE bit is when the TDRE bit
is set i.e. before writing the next byte in the DR.
ST72E121 ST72T121
SERIAL COMMUNICATIONS INTERFACE (Cont’d)
5.4.4.3 Receiver
The SCI can receive data words of either 8 or 9
bits. When the M bit is set, word length is 9 bits
and the MSB is stored in the R8 bit in the CR1 register.
Character reception
During a SCI reception, data shifts in least significant bit first through the RDI pin. In this mode, DR
register consists in a buffer (RDR) between the internal bus and the received shift register (see Figure 32).
Procedure
– Select the M bit to define the word length.
– Select the desired baud rate using the BRR and
the ERPR registers.
– Set the RE bit, this enables the receiver which
begins searching for a start bit.
When a character is received:
– The RDRF bit is set. It indicates that the content
of the shift register is transferred to the RDR.
– An interrupt is generated if the RIE bit is set and
the I bit is cleared in the CCR register.
– The error flags can be set if a frame error, noise
or an overrun error has been detected during reception.
Clearing the RDRF bit is performed by the following
software sequence done by:
1. An access to the SR register
2. A read to the DR register.
The RDRF bit must be cleared before the end of the
reception of the next character to avoid an overrun
error.
Break Character
When a break character is received, the SCI handles it as a framing error.
Idle Character
When a idle frame is detected, there is the same
procedure as a data received character plus an interrupt if the ILIE bit is set and the I bit is cleared in
the CCR register.
Overrun Error
An overrun error occurs when a character is received when RDRF has not been reset. Data can
not be transferred from the shift register to the
TDR register as long as the RDRF bit is not
cleared.
When a overrun error occurs:
– The OR bit is set.
– The RDR content will not be lost.
– The shift register will be overwritten.
– An interrupt is generated if the RIE bit is set and
the I bit is cleared in the CCR register.
The OR bit is reset by an access to the SR register
followed by a DR register read operation.
Noise Error
Oversampling techniques are used for data recovery by discriminating between valid incoming data
and noise.
When noise is detected in a frame:
– The NF is set at the rising edge of the RDRF bit.
– Data is transferred from the Shift register to the
DR register.
– No interrupt is generated. However this bit rises
at the same time as the RDRF bit which itself
generates an interrupt.
The NF bit is reset by a SR register read operation
followed by a DR register read operation.
Framing Error
A framing error is detected when:
– The stop bit is not recognized on reception at the
expected time, following either a de-synchronization or excessive noise.
– A break is received.
When the framing error is detected:
– the FE bit is set by hardware
– Data is transferred from the Shift register to the
DR register.
– No interrupt is generated. However this bit rises
at the same time as the RDRF bit which itself
generates an interrupt.
The FE bit is reset by a SR register read operation
followed by a DR register read operation.
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ST72E121 ST72T121
SERIAL COMMUNICATIONS INTERFACE (Cont’d)
Figure 34. SCI Baud Rate and Extended Prescaler Block Diagram
EXTENDED PRESCALER TRANSMITTER RATE CONTROL
ETPR
EXTENDED TRANSMITTER PRESCALER REGISTER
ERPR
EXTENDED RECEIVER PRESCALER REGISTER
EXTENDED PRESCALER RECEIVER RATE CONTROL
EXTENDED PRESCALER
fCPU
TRANSMITTER
CLOCK
TRANSMITTER RATE
CONTROL
/16
/2
/PR
BRR
SCP1 SCP0 SCT2 SCT1 SCT0 SCR2 SCR1SCR0
RECEIVER
CLOCK
RECEIVER RATE
CONTROL
CONVENTIONAL BAUD RATE GENERATOR
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ST72E121 ST72T121
SERIAL COMMUNICATIONS INTERFACE (Cont’d)
5.4.4.4 Conventional Baud Rate Generation
than zero. The baud rates are calculated as follows:
The baud rate for the receiver and transmitter (Rx
and Tx) are set independently and calculated as
fCPU
fCPU
follows:
Rx =
Tx =
fCPU
fCPU
16*ERPR
16*ETPR
Rx =
Tx =
(32*PR)*RR
(32*PR)*TR
with:
with:
ETPR = 1,..,255 (see ETPR register)
PR = 1, 3, 4 or 13 (see SCP0 & SCP1 bits)
ERPR = 1,.. 255 (see ERPR register)
TR = 1, 2, 4, 8, 16, 32, 64,128
5.4.4.6 Receiver Muting and Wake-up Feature
(see SCT0, SCT1 & SCT2 bits)
In multiprocessor configurations it is often desirable that only the intended message recipient
RR = 1, 2, 4, 8, 16, 32, 64,128
should actively receive the full message contents,
(see SCR0,SCR1 & SCR2 bits)
thus reducing redundant SCI service overhead for
All this bits are in the BRR register.
all non addressed receivers.
Example: If fCPU is 8 MHz (normal mode) and if
The non addressed devices may be placed in
PR=13 and TR=RR=1, the transmit and receive
sleep mode by means of the muting function.
baud rates are 19200 baud.
Setting the RWU bit by software puts the SCI in
Note: the baud rate registers MUST NOT be
sleep mode:
changed while the transmitter or the receiver is enAll the reception status bits can not be set.
abled.
All the receive interrupt are inhibited.
5.4.4.5 Extended Baud Rate Generation
A muted receiver may be awakened by one of the
The extended prescaler option gives a very fine
following two ways:
tuning on the baud rate, using a 255 value prescal– by Idle Line detection if the WAKE bit is reset,
er, whereas the conventional Baud Rate Generator retains industry standard software compatibili– by Address Mark detection if the WAKE bit is set.
ty.
Receiver wakes-up by Idle Line detection when
The extended baud rate generator block diagram
the Receive line has recognised an Idle Frame.
is described in the Figure 34.
Then the RWU bit is reset by hardware but the
IDLE bit is not set.
The output clock rate sent to the transmitter or to
the receiver will be the output from the 16 divider
Receiver wakes-up by Address Mark detection
divided by a factor ranging from 1 to 255 set in the
when it received a “1” as the most significant bit of
ERPR or the ETPR register.
a word, thus indicating that the message is an address. The reception of this particular word wakes
Note: the extended prescaler is activated by setup the receiver, resets the RWU bit and sets the
ting the ETPR or ERPR register to a value other
RDRF bit, which allows the receiver to receive this
word normally and to use it as an address word.
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ST72E121 ST72T121
SERIAL COMMUNICATIONS INTERFACE (Cont’d)
5.4.5 Low Power Modes
Mode
WAIT
HALT
Description
No effect on SCI.
SCI interrupts cause the device to exit from Wait mode.
SCI registers are frozen.
In Halt mode, the SCI stops transmitting/receiving until Halt mode is exited.
5.4.6 Interrupts
Interrupt Event
Transmit Data Register Empty
Transmission Complete
Received Data Ready to be Read
Overrrun Error Detected
Idle Line Detected
The SCI interrupt events are connected to the
same interrupt vector (see Interrupts chapter).
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Enable
Control
Bit
TDRE
TIE
TC
TCIE
RDRF
RIE
OR
IDLE
ILIE
Event
Flag
Exit
from
Wait
Yes
Yes
Yes
Yes
Yes
Exit
from
Halt
No
No
No
No
No
These events generate an interrupt if the corresponding Enable Control Bit is set and the interrupt mask in the CC register is reset (RIM instruction).
ST72E121 ST72T121
SERIAL COMMUNICATIONS INTERFACE (Cont’d)
5.4.7 Register Description
STATUS REGISTER (SR)
Read Only
Reset Value: 1100 0000 (C0h)
7
TDRE
0
TC
RDRF
IDLE
OR
NF
FE
-
Bit 7 = TDRE Transmit data register empty.
This bit is set by hardware when the content of the
TDR register has been transferred into the shift
register. An interrupt is generated if the TIE =1 in
the CR2 register. It is cleared by a software sequence (an access to the SR register followed by a
write to the DR register).
0: Data is not transferred to the shift register
1: Data is transferred to the shift register
Note: data will not be transferred to the shift register as long as the TDRE bit is not reset.
Bit 6 = TC Transmission complete.
This bit is set by hardware when transmission of a
frame containing Data, a Preamble or a Break is
complete. An interrupt is generated if TCIE=1 in
the CR2 register. It is cleared by a software sequence (an access to the SR register followed by a
write to the DR register).
0: Transmission is not complete
1: Transmission is complete
Bit 5 = RDRF Received data ready flag.
This bit is set by hardware when the content of the
RDR register has been transferred into the DR
register. An interrupt is generated if RIE=1 in the
CR2 register. It is cleared by a software sequence
(an access to the SR register followed by a read to
the DR register).
0: Data is not received
1: Received data is ready to be read
Bit 4 = IDLE Idle line detect.
This bit is set by hardware when a Idle Line is detected. An interrupt is generated if the ILIE=1 in
the CR2 register. It is cleared by a software sequence (an access to the SR register followed by a
read to the DR register).
0: No Idle Line is detected
1: Idle Line is detected
Note: The IDLE bit will not be set again until the
RDRF bit has been set itself (i.e. a new idle line occurs). This bit is not set by an idle line when the receiver wakes up from wake-up mode.
Bit 3 = OR Overrun error.
This bit is set by hardware when the word currently
being received in the shift register is ready to be
transferred into the RDR register while RDRF=1.
An interrupt is generated if RIE=1 in the CR2 register. It is cleared by a software sequence (an access to the SR register followed by a read to the
DR register).
0: No Overrun error
1: Overrun error is detected
Note: When this bit is set RDR register content will
not be lost but the shift register will be overwritten.
Bit 2 = NF Noise flag.
This bit is set by hardware when noise is detected
on a received frame. It is cleared by a software sequence (an access to the SR register followed by a
read to the DR register).
0: No noise is detected
1: Noise is detected
Note: This bit does not generate interrupt as it appears at the same time as the RDRF bit which itself generates an interrupt.
Bit 1 = FE Framing error.
This bit is set by hardware when a de-synchronization, excessive noise or a break character is detected. It is cleared by a software sequence (an
access to the SR register followed by a read to the
DR register).
0: No Framing error is detected
1: Framing error or break character is detected
Note: This bit does not generate interrupt as it appears at the same time as the RDRF bit which itself generates an interrupt. If the word currently
being transferred causes both frame error and
overrun error, it will be transferred and only the OR
bit will be set.
Bit 0 = Unused.
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ST72E121 ST72T121
SERIAL COMMUNICATIONS INTERFACE (Cont’d)
CONTROL REGISTER 1 (CR1)
1: An SCI interrupt is generated whenever TC=1 in
the SR register
Read/Write
Reset Value: Undefined
Bit 5 = RIE Receiver interrupt enable .
This bit is set and cleared by software.
7
0
0: interrupt is inhibited
1: An SCI interrupt is generated whenever OR=1
R8
T8
M
WAKE
or RDRF=1 in the SR register
Bit 7 = R8 Receive data bit 8.
This bit is used to store the 9th bit of the received
word when M=1.
Bit 6 = T8 Transmit data bit 8.
This bit is used to store the 9th bit of the transmitted word when M=1.
Bit 4 = M Word length.
This bit determines the word length. It is set or
cleared by software.
0: 1 Start bit, 8 Data bits, 1 Stop bit
1: 1 Start bit, 9 Data bits, 1 Stop bit
Bit 3 = WAKE Wake-Up method.
This bit determines the SCI Wake-Up method, it is
set or cleared by software.
0: Idle Line
1: Address Mark
CONTROL REGISTER 2 (CR2)
Read/Write
Reset Value: 0000 0000 (00 h)
7
TIE
0
TCIE
RIE
ILIE
TE
RE
RWU
SBK
Bit 7 = TIE Transmitter interrupt enable.
This bit is set and cleared by software.
0: interrupt is inhibited
1: An SCI interrupt is generated whenever
TDRE=1 in the SR register.
Bit 6 = TCIE Transmission complete interrupt enable
This bit is set and cleared by software.
0: interrupt is inhibited
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Bit 4 = ILIE Idle line interrupt enable.
This bit is set and cleared by software.
0: interrupt is inhibited
1: An SCI interrupt is generated whenever IDLE=1
in the SR register.
Bit 3 = TE Transmitter enable.
This bit enables the transmitter and assigns the
TDO pin to the alternate function. It is set and
cleared by software.
0: Transmitter is disabled, the TDO pin is back to
the I/O port configuration.
1: Transmitter is enabled
Note: during transmission, a “0” pulse on the TE
bit (“0” followed by “1”) sends a preamble after the
current word.
Bit 2 = RE Receiver enable.
This bit enables the receiver. It is set and cleared
by software.
0: Receiver is disabled.
1: Receiver is enabled and begins searching for a
start bit.
Bit 1 = RWU Receiver wake-up.
This bit determines if the SCI is in mute mode or
not. It is set and cleared by software and can be
cleared by hardware when a wake-up sequence is
recognized.
0: Receiver in active mode
1: Receiver in mute mode
Bit 0 = SBK Send break.
This bit set is used to send break characters. It is
set and cleared by software.
0: No break character is transmitted
1: Break characters are transmitted
Note: If the SBK bit is set to “1” and then to “0”, the
transmitter will send a BREAK word at the end of
the current word.
ST72E121 ST72T121
SERIAL COMMUNICATIONS INTERFACE (Cont’d)
DATA REGISTER (DR)
Read/Write
Reset Value: Undefined
Contains the Received or Transmitted data character, depending on whether it is read from or written to.
7
0
DR7
DR6
DR5
DR4
DR3
DR2
DR1
DR0
The Data register performs a double function (read
and write) since it is composed of two registers,
one for transmission (TDR) and one for reception
(RDR).
The TDR register provides the parallel interface
between the internal bus and the output shift register (see Figure 32).
The RDR register provides the parallel interface
between the input shift register and the internal
bus (see Figure 32).
BAUD RATE REGISTER (BRR)
Read/Write
Reset Value: 00xx xxxx (XXh)
7
0
SCP1
SCP0
SCT2
SCT1
SCT0
SCR2
SCR1 SCR0
Bit 7:6= SCP[1:0] First SCI Prescaler
These 2 prescaling bits allow several standard
clock division ranges:
PR Prescaling factor
SCP1
SCP0
1
0
0
3
0
1
4
1
0
13
1
1
Bit 5:3 = SCT[2:0] SCI Transmitter rate divisor
These 3 bits, in conjunction with the SCP1 & SCP0
bits define the total division applied to the bus
clock to yield the transmit rate clock in conventional Baud Rate Generator mode.
TR dividing factor
SCT2
SCT1
SCT0
1
0
0
0
2
0
0
1
4
0
1
0
8
0
1
1
16
1
0
0
32
1
0
1
64
1
1
0
128
1
1
1
Note: this TR factor is used only when the ETPR
fine tuning factor is equal to 00h; otherwise, TR is
replaced by the ETPR dividing factor.
Bit 2:0 = SCR[2:0] SCI Receiver rate divisor.
These 3 bits, in conjunction with the SCP1 & SCP0
bits define the total division applied to the bus
clock to yield the receive rate clock in conventional
Baud Rate Generator mode.
RR dividing factor
SCR2
SCR1
SCR0
1
0
0
0
2
0
0
1
4
0
1
0
8
0
1
1
16
1
0
0
32
1
0
1
64
1
1
0
128
1
1
1
Note: this RR factor is used only when the ERPR
fine tuning factor is equal to 00h; otherwise, RR is
replaced by the ERPR dividing factor.
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ST72E121 ST72T121
SERIAL COMMUNICATIONS INTERFACE (Cont’d)
EXTENDED RECEIVE PRESCALER DIVISION
REGISTER (ERPR)
Read/Write
Reset Value: 0000 0000 (00 h)
Allows setting of the Extended Prescaler rate division factor for the receive circuit.
7
EXTENDED TRANSMIT PRESCALER DIVISION
REGISTER (ETPR)
Read/Write
Reset Value:0000 0000 (00h)
Allows setting of the External Prescaler rate division factor for the transmit circuit.
0
7
ERPR ERPR ERPR ERPR ERPR ERPR ERPR ERPR
7
6
5
4
3
2
1
0
0
ETPR
7
Bit 7:1 = ERPR[7:0] 8-bit Extended Receive Prescaler Register.
The extended Baud Rate Generator is activated
when a value different from 00h is stored in this
register. Therefore the clock frequency issued
from the 16 divider (see Figure 34) is divided by
the binary factor set in the ERPR register (in the
range 1 to 255).
The extended baud rate generator is not used after a reset.
ETPR
6
ETPR
5
ETPR
4
ETPR
3
ETPR
2
ETPR ETPR
1
0
Bit 7:1 = ETPR[7:0] 8-bit Extended Transmit Prescaler Register.
The extended Baud Rate Generator is activated
when a value different from 00h is stored in this
register. Therefore the clock frequency issued
from the 16 divider (see Figure 34) is divided by
the binary factor set in the ETPR register (in the
range 1 to 255).
The extended baud rate generator is not used after a reset.
Table 16. SCI Register Map and Reset Values
Address
(Hex.)
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Register
Name
7
6
5
4
3
2
1
0
50
SR
Reset Value
TDRE
1
TC
1
RDRF
0
IDLE
0
OR
0
NF
0
FE
0
0
51
DR
Reset Value
DR7
-
DR6
-
DR5
-
DR4
-
DR3
-
DR2
-
DR1
-
DR0
-
52
BRR
Reset Value
SCP1
0
SCP0
0
SCT2
x
SCT1
x
SCT0
x
SCR2
x
SCR1
x
SCR0
x
53
CR1
Reset Value
R8
-
T8
-
-
M
-
WAKE
-
-
-
-
54
CR2
Reset Value
TIE
0
TCIE
0
RIE
0
ILIE
0
TE
0
RE
0
RWU
0
SBK
0
55
ERPR
Reset Value
ERPR7
0
ERPR6
0
ERPR5
0
ERPR4
0
ERPR3
0
ERPR2
0
ERPR1
0
ERPR0
0
57
ETPR
Reset Value
ETPR7
0
ETPR6
0
ETPR5
0
ETPR4
0
ETPR3
0
ETPR2
0
ETPR1
0
ETPR0
0
ST72E121 ST72T121
5.5 SERIAL PERIPHERAL INTERFACE (SPI)
5.5.1 Introduction
The Serial Peripheral Interface (SPI) allows fullduplex, synchronous, serial communication with
external devices. An SPI system may consist of a
master and one or more slaves or a system in
which devices may be either masters or slaves.
The SPI is normally used for communication between the microcontroller and external peripherals
or another microcontroller.
Refer to the Pin Description chapter for the devicespecific pin-out.
5.5.3 General description
The SPI is connected to external devices through
4 alternate pins:
– MISO: Master In Slave Out pin
– MOSI: Master Out Slave In pin
– SCK: Serial Clock pin
– SS: Slave select pin
A basic example of interconnections between a
single master and a single slave is illustrated on
Figure 35.
The MOSI pins are connected together as are
MISO pins. In this way data is transferred serially
between master and slave (most significant bit
first).
When the master device transmits data to a slave
device via MOSI pin, the slave device responds by
sending data to the master device via the MISO
pin. This implies full duplex transmission with both
data out and data in synchronized with the same
clock signal (which is provided by the master device via the SCK pin).
Thus, the byte transmitted is replaced by the byte
received and eliminates the need for separate
transmit-empty and receiver-full bits. A status flag
is used to indicate that the I/O operation is complete.
Four possible data/clock timing relationships may
be chosen (see Figure 38) but master and slave
must be programmed with the same timing mode.
5.5.2 Main Features
■ Full duplex, three-wire synchronous transfers
■ Master or slave operation
■ Four master mode frequencies
■ Maximum slave mode frequency = fCPU/2.
■ Four programmable master bit rates
■ Programmable clock polarity and phase
■ End of transfer interrupt flag
■ Write collision flag protection
■ Master mode fault protection capability.
Figure 35. Serial Peripheral Interface Master/Slave
SLAVE
MASTER
MSBit
LSBit
8-BIT SHIFT REGISTER
SPI
CLOCK
GENERATOR
MSBit
MISO
MISO
MOSI
MOSI
SCK
SS
LSBit
8-BIT SHIFT REGISTER
SCK
+5V
SS
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ST72E121 ST72T121
SERIAL PERIPHERAL INTERFACE (Cont’d)
Figure 36. Serial Peripheral Interface Block Diagram
Internal Bus
Read
DR
IT
Read Buffer
request
MOSI
MISO
SR
8-Bit Shift Register
SPIF WCOL - MODF
-
-
-
-
Write
SPI
STATE
CONTROL
SCK
SS
CR
SPIE
MASTER
CONTROL
SERIAL
CLOCK
GENERATOR
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SPE
SPR2 MSTR CPOL CPHA SPR1 SPR0
ST72E121 ST72T121
SERIAL PERIPHERAL INTERFACE (Cont’d)
5.5.4 Functional Description
Figure 35 shows the serial peripheral interface
(SPI) block diagram.
This interface contains 3 dedicated registers:
– A Control Register (CR)
– A Status Register (SR)
– A Data Register (DR)
Refer to the CR, SR and DR registers in Section
5.5.7for the bit definitions.
5.5.4.1 Master Configuration
In a master configuration, the serial clock is generated on the SCK pin.
Procedure
– Select the SPR0 & SPR1 bits to define the serial clock baud rate (see CR register).
– Select the CPOL and CPHA bits to define one
of the four relationships between the data
transfer and the serial clock (see Figure 38).
– The SS pin must be connected to a high level
signal during the complete byte transmit sequence.
– The MSTR and SPE bits must be set (they remain set only if the SS pin is connected to a
high level signal).
In this configuration the MOSI pin is a data output
and to the MISO pin is a data input.
Transmit sequence
The transmit sequence begins when a byte is written the DR register.
The data byte is parallel loaded into the 8-bit shift
register (from the internal bus) during a write cycle
and then shifted out serially to the MOSI pin most
significant bit first.
When data transfer is complete:
– The SPIF bit is set by hardware
– An interrupt is generated if the SPIE bit is set
and the I bit in the CCR register is cleared.
During the last clock cycle the SPIF bit is set, a
copy of the data byte received in the shift register
is moved to a buffer. When the DR register is read,
the SPI peripheral returns this buffered value.
Clearing the SPIF bit is performed by the following
software sequence:
1. An access to the SR register while the SPIF bit
is set
2. A read to the DR register.
Note: While the SPIF bit is set, all writes to the DR
register are inhibited until the SR register is read.
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ST72E121 ST72T121
SERIAL PERIPHERAL INTERFACE (Cont’d)
5.5.4.2 Slave Configuration
In slave configuration, the serial clock is received
on the SCK pin from the master device.
The value of the SPR0 & SPR1 bits is not used for
the data transfer.
Procedure
– For correct data transfer, the slave device
must be in the same timing mode as the master device (CPOL and CPHA bits). See Figure
38.
– The SS pin must be connected to a low level
signal during the complete byte transmit sequence.
– Clear the MSTR bit and set the SPE bit to assign the pins to alternate function.
In this configuration the MOSI pin is a data input
and the MISO pin is a data output.
Transmit Sequence
The data byte is parallel loaded into the 8-bit shift
register (from the internal bus) during a write cycle
and then shifted out serially to the MISO pin most
significant bit first.
The transmit sequence begins when the slave device receives the clock signal and the most significant bit of the data on its MOSI pin.
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When data transfer is complete:
– The SPIF bit is set by hardware
– An interrupt is generated if SPIE bit is set and
I bit in CCR register is cleared.
During the last clock cycle the SPIF bit is set, a
copy of the data byte received in the shift register
is moved to a buffer. When the DR register is read,
the SPI peripheral returns this buffered value.
Clearing the SPIF bit is performed by the following
software sequence:
1. An access to the SR register while the SPIF bit
is set.
2.A read to the DR register.
Notes: While the SPIF bit is set, all writes to the
DR register are inhibited until the SR register is
read.
The SPIF bit can be cleared during a second
transmission; however, it must be cleared before
the second SPIF bit in order to prevent an overrun
condition (see Section 5.5.4.6).
Depending on the CPHA bit, the SS pin has to be
set to write to the DR register between each data
byte transfer to avoid a write collision (see Section
5.5.4.4).
ST72E121 ST72T121
SERIAL PERIPHERAL INTERFACE (Cont’d)
5.5.4.3 Data Transfer Format
During an SPI transfer, data is simultaneously
transmitted (shifted out serially) and received
(shifted in serially). The serial clock is used to synchronize the data transfer during a sequence of
eight clock pulses.
The SS pin allows individual selection of a slave
device; the other slave devices that are not selected do not interfere with the SPI transfer.
Clock Phase and Clock Polarity
Four possible timing relationships may be chosen
by software, using the CPOL and CPHA bits.
The CPOL (clock polarity) bit controls the steady
state value of the clock when no data is being
transferred. This bit affects both master and slave
modes.
The combination between the CPOL and CPHA
(clock phase) bits selects the data capture clock
edge.
Figure 38, shows an SPI transfer with the four
combinations of the CPHA and CPOL bits. The diagram may be interpreted as a master or slave
timing diagram where the SCK pin, the MISO pin,
the MOSI pin are directly connected between the
master and the slave device.
The SS pin is the slave device select input and can
be driven by the master device.
The master device applies data to its MOSI pinclock edge before the capture clock edge.
CPHA bit is set
The second edge on the SCK pin (falling edge if
the CPOL bit is reset, rising edge if the CPOL bit is
set) is the MSBit capture strobe. Data is latched on
the occurrence of the second clock transition.
No write collision should occur even if the SS pin
stays low during a transfer of several bytes (see
Figure 37).
CPHA bit is reset
The first edge on the SCK pin (falling edge if CPOL
bit is set, rising edge if CPOL bit is reset) is the
MSBit capture strobe. Data is latched on the occurrence of the first clock transition.
The SS pin must be toggled high and low between
each byte transmitted (see Figure 37).
To protect the transmission from a write collision a
low value on the SS pin of a slave device freezes
the data in its DR register and does not allow it to
be altered. Therefore the SS pin must be high to
write a new data byte in the DR without producing
a write collision.
Figure 37. CPHA / SS Timing Diagram
MOSI/MISO
Byte 1
Byte 2
Byte 3
Master SS
Slave SS
(CPHA=0)
Slave SS
(CPHA=1)
VR02131A
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ST72E121 ST72T121
SERIAL PERIPHERAL INTERFACE (Cont’d)
Figure 38. Data Clock Timing Diagram
CPHA =1
SCLK (with
CPOL = 1)
SCLK (with
CPOL = 0)
MISO
(from master)
MOSI
(from slave)
MSBit
Bit 6
Bit 5
Bit 4
Bit3
Bit 2
Bit 1
LSBit
MSBit
Bit 6
Bit 5
Bit 4
Bit3
Bit 2
Bit 1
LSBit
SS
(to slave)
CAPTURE STROBE
CPHA =0
CPOL = 1
CPOL = 0
MSBit
MISO
(from master)
MOSI
(from slave)
MSBit
Bit 6
Bit 5
Bit 4
Bit3
Bit 2
Bit 1
LSBit
Bit 6
Bit 5
Bit 4
Bit3
Bit 2
Bit 1
LSBit
SS
(to slave)
CAPTURE STROBE
Note: This figure should not be used as a replacement for parametric information.
Refer to the Electrical Characteristics chapter.
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VR02131B
ST72E121 ST72T121
SERIAL PERIPHERAL INTERFACE (Cont’d)
5.5.4.4 Write Collision Error
A write collision occurs when the software tries to
write to the DR register while a data transfer is taking place with an external device. When this happens, the transfer continues uninterrupted; and
the software write will be unsuccessful.
Write collisions can occur both in master and slave
mode.
Note: a "read collision" will never occur since the
received data byte is placed in a buffer in which
access is always synchronous with the MCU operation.
In Slave mode
When the CPHA bit is set:
The slave device will receive a clock (SCK) edge
prior to the latch of the first data transfer. This first
clock edge will freeze the data in the slave device
DR register and output the MSBit on to the external MISO pin of the slave device.
The SS pin low state enables the slave device but
the output of the MSBit onto the MISO pin does
not take place until the first data transfer clock
edge.
When the CPHA bit is reset:
Data is latched on the occurrence of the first clock
transition. The slave device does not have any
way of knowing when that transition will occur;
therefore, the slave device collision occurs when
software attempts to write the DR register after its
SS pin has been pulled low.
For this reason, the SS pin must be high, between
each data byte transfer, to allow the CPU to write
in the DR register without generating a write collision.
In Master mode
Collision in the master device is defined as a write
of the DR register while the internal serial clock
(SCK) is in the process of transfer.
The SS pin signal must be always high on the
master device.
WCOL bit
The WCOL bit in the SR register is set if a write
collision occurs.
No SPI interrupt is generated when the WCOL bit
is set (the WCOL bit is a status flag only).
Clearing the WCOL bit is done through a software
sequence (see Figure 39).
Figure 39. Clearing the WCOL bit (Write Collision Flag) Software Sequence
Clearing sequence after SPIF = 1 (end of a data byte transfer)
1st Step
Read SR
OR
Read SR
THEN
THEN
2nd Step
Read DR
SPIF =0
WCOL=0
Write DR
SPIF =0
WCOL=0 if no transfer has started
WCOL=1 if a transfer has started
before the 2nd step
Clearing sequence before SPIF = 1 (during a data byte transfer)
1st Step
Read SR
THEN
2nd Step
Read DR
WCOL=0
Note: Writing in DR register instead of reading in it do not reset
WCOL bit
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ST72E121 ST72T121
SERIAL PERIPHERAL INTERFACE (Cont’d)
5.5.4.5 Master Mode Fault
Master mode fault occurs when the master device
has its SS pin pulled low, then the MODF bit is set.
Master mode fault affects the SPI peripheral in the
following ways:
– The MODF bit is set and an SPI interrupt is
generated if the SPIE bit is set.
– The SPE bit is reset. This blocks all output
from the device and disables the SPI peripheral.
– The MSTR bit is reset, thus forcing the device
into slave mode.
Clearing the MODF bit is done through a software
sequence:
1. A read or write access to the SR register while
the MODF bit is set.
2. A write to the CR register.
Notes: To avoid any multiple slave conflicts in the
case of a system comprising several MCUs, the
SS pin must be pulled high during the clearing sequence of the MODF bit. The SPE and MSTR bits
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may be restored to their original state during or after this clearing sequence.
Hardware does not allow the user to set the SPE
and MSTR bits while the MODF bit is set except in
the MODF bit clearing sequence.
In a slave device the MODF bit can not be set, but
in a multi master configuration the device can be in
slave mode with this MODF bit set.
The MODF bit indicates that there might have
been a multi-master conflict for system control and
allows a proper exit from system operation to a reset or default system state using an interrupt routine.
5.5.4.6 Overrun Condition
An overrun condition occurs when the master device has sent several data bytes and the slave device has not cleared the SPIF bit issuing from the
previous data byte transmitted.
In this case, the receiver buffer contains the byte
sent after the SPIF bit was last cleared. A read to
the DR register returns this byte. All other bytes
are lost.
This condition is not detected by the SPI peripheral.
ST72E121 ST72T121
SERIAL PERIPHERAL INTERFACE (Cont’d)
5.5.4.7 Single Master and Multimaster Configurations
For more security, the slave device may respond
There are two types of SPI systems:
to the master with the received data byte. Then the
– Single Master System
master will receive the previous byte back from the
– Multimaster System
slave device if all MISO and MOSI pins are connected and the slave has not written its DR register.
Single Master System
Other transmission security methods can use
A typical single master system may be configured,
ports for handshake lines or data bytes with comusing an MCU as the master and four MCUs as
mand fields.
slaves (see Figure 40).
Multi-master System
The master device selects the individual slave deA multi-master system may also be configured by
vices by using four pins of a parallel port to control
the user. Transfer of master control could be imthe four SS pins of the slave devices.
plemented using a handshake method through the
The SS pins are pulled high during reset since the
I/O ports or by an exchange of code messages
master device ports will be forced to be inputs at
through the serial peripheral interface system.
that time, thus disabling the slave devices.
The multi-master system is principally handled by
the MSTR bit in the CR register and the MODF bit
Note: To prevent a bus conflict on the MISO line
in the SR register.
the master allows only one active slave device
during a transmission.
Figure 40. Single Master Configuration
SS
SCK
SS
SS
SCK
Slave
MCU
Slave
MCU
MOSI MISO
MOSI MISO
SS
SCK
Slave
MCU
SCK
Slave
MCU
MOSI MISO
MOSI MISO
SCK
Master
MCU
5V
Ports
MOSI MISO
SS
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ST72E121 ST72T121
SERIAL PERIPHERAL INTERFACE (Cont’d)
5.5.5 Low Power Modes
Mode
WAIT
HALT
Description
No effect on SPI.
SPI interrupt events cause the device to exit from WAIT mode.
SPI registers are frozen.
In HALT mode, the SPI is inactive. SPI operation resumes when the MCU is woken up by an interrupt with
“exit from HALT mode” capability.
5.5.6 Interrupts
Interrupt Event
SPI End of Transfer Event
Master Mode Fault Event
Note: The SPI interrupt events are connected to
the same interrupt vector (see Interrupts chapter).
They generate an interrupt if the corresponding
Enable Control Bit is set and the interrupt mask in
the CC register is reset (RIM instruction).
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Event
Flag
Enable
Control
Bit
SPIF
MODF
SPIE
Exit
from
Wait
Yes
Yes
Exit
from
Halt
No
No
ST72E121 ST72T121
SERIAL PERIPHERAL INTERFACE (Cont’d)
5.5.7 Register Description
CONTROL REGISTER (CR)
Read/Write
Reset Value: 0000xxxx (0xh)
7
SPIE
0
SPE
SPR2
MSTR
CPOL
CPHA
SPR1
SPR0
Bit 7 = SPIE Serial peripheral interrupt enable.
This bit is set and cleared by software.
0: Interrupt is inhibited
1: An SPI interrupt is generated whenever SPIF=1
or MODF=1 in the SR register
Bit 6 = SPE Serial peripheral output enable.
This bit is set and cleared by software. It is also
cleared by hardware when, in master mode, SS=0
(see Section 5.5.4.5 Master Mode Fault).
0: I/O port connected to pins
1: SPI alternate functions connected to pins
The SPE bit is cleared by reset, so the SPI peripheral is not initially connected to the external pins.
Bit 5 = SPR2 Divider Enable.
this bit is set and cleared by software and it is
cleared by reset. It is used with the SPR[1:0] bits to
set the baud rate. Refer to Table 17.
0: Divider by 2 enabled
1: Divider by 2 disabled
Bit 4 = MSTR Master.
This bit is set and cleared by software. It is also
cleared by hardware when, in master mode, SS=0
(see Section 5.5.4.5 Master Mode Fault).
0: Slave mode is selected
1: Master mode is selected, the function of the
SCK pin changes from an input to an output and
the functions of the MISO and MOSI pins are reversed.
Bit 3 = CPOL Clock polarity.
This bit is set and cleared by software. This bit determines the steady state of the serial Clock. The
CPOL bit affects both the master and slave
modes.
0: The steady state is a low value at the SCK pin.
1: The steady state is a high value at the SCK pin.
Bit 2 = CPHA Clock phase.
This bit is set and cleared by software.
0: The first clock transition is the first data capture
edge.
1: The second clock transition is the first capture
edge.
Bit 1:0 = SPR[1:0] Serial peripheral rate.
These bits are set and cleared by software.Used
with the SPR2 bit, they select one of six baud rates
to be used as the serial clock when the device is a
master.
These 2 bits have no effect in slave mode.
Table 17. Serial Peripheral Baud Rate
Serial Clock
SPR2
SPR1
SPR0
fCPU/4
1
0
0
fCPU/8
0
0
0
fCPU/16
0
0
1
fCPU/32
1
1
0
fCPU/64
0
1
0
fCPU/128
0
1
1
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ST72E121 ST72T121
SERIAL PERIPHERAL INTERFACE (Cont’d)
STATUS REGISTER (SR)
Read Only
Reset Value: 0000 0000 (00h)
7
SPIF
WCOL
-
MODF
-
-
-
DATA I/O REGISTER (DR)
Read/Write
Reset Value: Undefined
0
7
-
D7
Bit 7 = SPIF Serial Peripheral data transfer flag.
This bit is set by hardware when a transfer has
been completed. An interrupt is generated if
SPIE=1 in the CR register. It is cleared by a software sequence (an access to the SR register followed by a read or write to the DR register).
0: Data transfer is in progress or has been approved by a clearing sequence.
1: Data transfer between the device and an external device has been completed.
Note: While the SPIF bit is set, all writes to the DR
register are inhibited.
Bit 6 = WCOL Write Collision status.
This bit is set by hardware when a write to the DR
register is done during a transmit sequence. It is
cleared by a software sequence (see Figure 39).
0: No write collision occurred
1: A write collision has been detected
Bit 5 = Unused.
Bit 4 = MODF Mode Fault flag.
This bit is set by hardware when the SS pin is
pulled low in master mode (see Section 5.5.4.5
Master Mode Fault). An SPI interrupt can be generated if SPIE=1 in the CR register. This bit is
cleared by a software sequence (An access to the
SR register while MODF=1 followed by a write to
the CR register).
0: No master mode fault detected
1: A fault in master mode has been detected
Bits 3-0 = Unused.
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0
D6
D5
D4
D3
D2
D1
D0
The DR register is used to transmit and receive
data on the serial bus. In the master device only a
write to this register will initiate transmission/reception of another byte.
Notes: During the last clock cycle the SPIF bit is
set, a copy of the received data byte in the shift
register is moved to a buffer. When the user reads
the serial peripheral data I/O register, the buffer is
actually being read.
Warning:
A write to the DR register places data directly into
the shift register for transmission.
A write to the the DR register returns the value located in the buffer and not the contents of the shift
register (See Figure 36 ).
ST72E121 ST72T121
SERIAL PERIPHERAL INTERFACE (Cont’d)
Table 18. SPI Register Map and Reset Values
Address
(Hex.)
21
22
23
Register
Name
7
6
5
4
3
2
1
0
DR
Reset Value
CR
Reset Value
SR
Reset Value
D7
x
SPIE
0
SPIF
0
D6
x
SPE
0
WCOL
0
D5
x
SPR2
0
0
D4
x
MSTR
0
MODF
0
D3
x
CPOL
x
0
D2
x
CPHA
x
0
D1
x
SPR1
x
0
D0
x
SPR0
x
0
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ST72E121 ST72T121
6 INSTRUCTION SET
6.1 ST7 ADDRESSING MODES
The ST7 Core features 17 different addressing
modes which can be classified in 7 main groups:
Addressing Mode
Example
Inherent
nop
Immediate
ld A,#$55
Direct
ld A,$55
Indexed
ld A,($55,X)
Indirect
ld A,([$55],X)
Relative
jrne loop
Bit operation
bset
byte,#5
The ST7 Instruction set is designed to minimize
the number of bytes required per instruction: To do
so, most of the addressing modes may be subdivided in two sub-modes called long and short:
– Long addressing mode is more powerful because it can use the full 64 Kbyte address space,
however it uses more bytes and more CPU cycles.
– Short addressing mode is less powerful because
it can generally only access page zero (0000h 00FFh range), but the instruction size is more
compact, and faster. All memory to memory instructions use short addressing modes only
(CLR, CPL, NEG, BSET, BRES, BTJT, BTJF,
INC, DEC, RLC, RRC, SLL, SRL, SRA, SWAP)
The ST7 Assembler optimizes the use of long and
short addressing modes.
Table 19. ST7 Addressing Mode Overview
Mode
Syntax
Pointer
Address
(Hex.)
Destination/
Source
Pointer
Size
(Hex.)
Length
(Bytes)
Inherent
nop
+0
Immediate
ld A,#$55
+1
Short
Direct
ld A,$10
00..FF
+1
Long
Direct
ld A,$1000
0000..FFFF
+2
No Offset
Direct
Indexed
ld A,(X)
00..FF
+ 0 (with X register)
+ 1 (with Y register)
Short
Direct
Indexed
ld A,($10,X)
00..1FE
+1
Long
Direct
Indexed
Short
Indirect
ld A,($1000,X)
0000..FFFF
ld A,[$10]
00..FF
+2
00..FF
byte
+2
Long
Indirect
ld A,[$10.w]
0000..FFFF
00..FF
word
+2
Short
Indirect
Indexed
ld A,([$10],X)
00..1FE
00..FF
byte
+2
Long
Indirect
Indexed
ld A,([$10.w],X)
0000..FFFF
00..FF
word
+2
00..FF
byte
00..FF
byte
1)
Relative
Direct
jrne loop
PC-128/PC+127
Relative
Indirect
jrne [$10]
PC-128/PC+1271)
Bit
Direct
bset $10,#7
00..FF
Bit
Indirect
bset [$10],#7
00..FF
Bit
Direct
Relative
btjt $10,#7,skip
00..FF
Bit
Indirect
Relative
btjt [$10],#7,skip 00..FF
+1
+2
+1
+2
+2
00..FF
byte
+3
Note 1. At the time the instruction is executed, the Program Counter (PC) points to the instruction following JRxx.
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ST7 ADDRESSING MODES (Cont’d)
6.1.1 Inherent
All Inherent instructions consist of a single byte.
The opcode fully specifies all the required information for the CPU to process the operation.
Inherent Instruction
Function
NOP
No operation
TRAP
S/W Interrupt
WFI
Wait For Interrupt (Low Power
Mode)
HALT
Halt Oscillator (Lowest Power
Mode)
RET
Sub-routine Return
IRET
Interrupt Sub-routine Return
SIM
Set Interrupt Mask
RIM
Reset Interrupt Mask
SCF
Set Carry Flag
RCF
Reset Carry Flag
RSP
Reset Stack Pointer
LD
Load
CLR
Clear
PUSH/POP
Push/Pop to/from the stack
INC/DEC
Increment/Decrement
TNZ
Test Negative or Zero
CPL, NEG
1 or 2 Complement
MUL
Byte Multiplication
SLL, SRL, SRA, RLC,
RRC
Shift and Rotate Operations
SWAP
Swap Nibbles
6.1.2 Immediate
Immediate instructions have two bytes, the first
byte contains the opcode, the second byte contains the operand value.
Immediate Instruction
Function
LD
Load
CP
Compare
BCP
Bit Compare
AND, OR, XOR
Logical Operations
ADC, ADD, SUB, SBC
Arithmetic Operations
6.1.3 Direct
In Direct instructions, the operands are referenced
by their memory address.
The direct addressing mode consists of two submodes:
Direct (short)
The address is a byte, thus requires only one byte
after the opcode, but only allows 00 - FF addressing space.
Direct (long)
The address is a word, thus allowing 64 Kbyte addressing space, but requires 2 bytes after the opcode.
6.1.4 Indexed (No Offset, Short, Long)
In this mode, the operand is referenced by its
memory address, which is defined by the unsigned
addition of an index register (X or Y) with an offset.
The indirect addressing mode consists of three
sub-modes:
Indexed (No Offset)
There is no offset, (no extra byte after the opcode),
and allows 00 - FF addressing space.
Indexed (Short)
The offset is a byte, thus requires only one byte after the opcode and allows 00 - 1FE addressing
space.
Indexed (long)
The offset is a word, thus allowing 64 Kbyte addressing space and requires 2 bytes after the opcode.
6.1.5 Indirect (Short, Long)
The required data byte to do the operation is found
by its memory address, located in memory (pointer).
The pointer address follows the opcode. The indirect addressing mode consists of two sub-modes:
Indirect (short)
The pointer address is a byte, the pointer size is a
byte, thus allowing 00 - FF addressing space, and
requires 1 byte after the opcode.
Indirect (long)
The pointer address is a byte, the pointer size is a
word, thus allowing 64 Kbyte addressing space,
and requires 1 byte after the opcode.
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ST72E121 ST72T121
ST7 ADDRESSING MODES (Cont’d)
6.1.6 Indirect Indexed (Short, Long)
This is a combination of indirect and short indexed
addressing modes. The operand is referenced by
its memory address, which is defined by the unsigned addition of an index register value (X or Y)
with a pointer value located in memory. The pointer address follows the opcode.
The indirect indexed addressing mode consists of
two sub-modes:
Indirect Indexed (Short)
The pointer address is a byte, the pointer size is a
byte, thus allowing 00 - 1FE addressing space,
and requires 1 byte after the opcode.
Indirect Indexed (Long)
The pointer address is a byte, the pointer size is a
word, thus allowing 64 Kbyte addressing space,
and requires 1 byte after the opcode.
Table 20. Instructions Supporting Direct,
Indexed, Indirect and Indirect Indexed
Addressing Modes
Long and Short
Instructions
Function
LD
Load
CP
Compare
AND, OR, XOR
Logical Operations
ADC, ADD, SUB, SBC
Arithmetic Addition/subtraction operations
BCP
Bit Compare
Short Instructions Only
Function
CLR
Clear
INC, DEC
Increment/Decrement
TNZ
Test Negative or Zero
CPL, NEG
1 or 2 Complement
BSET, BRES
Bit Operations
BTJT, BTJF
Bit Test and Jump Operations
SLL, SRL, SRA, RLC,
RRC
Shift and Rotate Operations
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SWAP
Swap Nibbles
CALL, JP
Call or Jump subroutine
6.1.7 Relative Mode (Direct, Indirect)
This addressing mode is used to modify the PC
register value by adding an 8-bit signed offset to it.
Available Relative Direct/
Indirect Instructions
Function
JRxx
Conditional Jump
CALLR
Call Relative
The relative addressing mode consists of two submodes:
Relative (Direct)
The offset follows the opcode.
Relative (Indirect)
The offset is defined in memory, of which the address follows the opcode.
ST72E121 ST72T121
6.2 INSTRUCTION GROUPS
The ST7 family devices use an Instruction Set
consisting of 63 instructions. The instructions may
be subdivided into 13 main groups as illustrated in
the following table:
Load and Transfer
LD
CLR
Stack operation
PUSH
POP
Increment/Decrement
INC
DEC
Compare and Tests
CP
TNZ
BCP
Logical operations
AND
OR
XOR
CPL
NEG
Bit Operation
BSET
BRES
Conditional Bit Test and Branch
BTJT
BTJF
Arithmetic operations
ADC
ADD
SUB
SBC
MUL
Shift and Rotates
SLL
SRL
SRA
RLC
RRC
SWAP
SLA
Unconditional Jump or Call
JRA
JRT
JRF
JP
CALL
CALLR
NOP
Conditional Branch
JRxx
Interruption management
TRAP
WFI
HALT
IRET
Code Condition Flag modification
SIM
RIM
SCF
RCF
Using a pre-byte
The instructions are described with one to four
bytes.
In order to extend the number of available opcodes for an 8-bit CPU (256 opcodes), three different prebyte opcodes are defined. These prebytes
modify the meaning of the instruction they precede.
The whole instruction becomes:
PC-2 End of previous instruction
PC-1 Prebyte
PC
Opcode
PC+1 Additional word (0 to 2) according to the
number of bytes required to compute the
effective address
RSP
RET
These prebytes enable instruction in Y as well as
indirect addressing modes to be implemented.
They precede the opcode of the instruction in X or
the instruction using direct addressing mode. The
prebytes are:
PDY 90 Replace an X based instruction using
immediate, direct, indexed, or inherent
addressing mode by a Y one.
PIX 92 Replace an instruction using direct, direct bit, or direct relative addressing
mode to an instruction using the corresponding indirect addressing mode.
It also changes an instruction using X
indexed addressing mode to an instruction using indirect X indexed addressing
mode.
PIY 91 Replace an instruction using X indirect
indexed addressing mode by a Y one.
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ST72E121 ST72T121
INSTRUCTION GROUPS (Cont’d)
Mnemo
Description
Function/Example
Dst
Src
H
I
N
Z
C
ADC
Add with Carry
A=A+M+C
A
M
H
N
Z
C
ADD
Addition
A=A+M
A
M
H
N
Z
C
AND
Logical And
A=A.M
A
M
N
Z
BCP
Bit compare A, Memory
tst (A . M)
A
M
N
Z
BRES
Bit Reset
bres Byte, #3
M
BSET
Bit Set
bset Byte, #3
M
BTJF
Jump if bit is false (0)
btjf Byte, #3, Jmp1
M
C
BTJT
Jump if bit is true (1)
btjt Byte, #3, Jmp1
M
C
CALL
Call subroutine
CALLR
Call subroutine relative
CLR
Clear
CP
Arithmetic Compare
tst(Reg - M)
reg
reg, M
CPL
One Complement
A = FFH-A
DEC
Decrement
dec Y
HALT
Halt
IRET
Interrupt routine return
Pop CC, A, X, PC
INC
Increment
inc X
JP
Absolute Jump
jp [TBL.w]
JRA
Jump relative always
JRT
Jump relative
JRF
Never jump
JRIH
Jump if ext. interrupt = 1
JRIL
Jump if ext. interrupt = 0
JRH
Jump if H = 1
H=1?
JRNH
Jump if H = 0
H=0?
JRM
Jump if I = 1
I=1?
JRNM
Jump if I = 0
I=0?
JRMI
Jump if N = 1 (minus)
N=1?
JRPL
Jump if N = 0 (plus)
N=0?
JREQ
Jump if Z = 1 (equal)
Z=1?
JRNE
Jump if Z = 0 (not equal)
Z=0?
JRC
Jump if C = 1
C=1?
JRNC
Jump if C = 0
C=0?
JRULT
Jump if C = 1
Unsigned <
JRUGE
Jump if C = 0
Jmp if unsigned >=
JRUGT
Jump if (C + Z = 0)
Unsigned >
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0
1
N
Z
C
reg, M
N
Z
1
reg, M
N
Z
N
Z
N
Z
M
0
jrf *
H
reg, M
I
C
ST72E121 ST72T121
INSTRUCTION GROUPS (Cont’d)
Mnemo
Description
Function/Example
Dst
Src
JRULE
Jump if (C + Z = 1)
Unsigned <=
LD
Load
dst <= src
reg, M
M, reg
MUL
Multiply
X,A = X * A
A, X, Y
X, Y, A
NEG
Negate (2’s compl)
neg $10
reg, M
NOP
No Operation
OR
OR operation
A=A+M
A
M
POP
Pop from the Stack
pop reg
reg
M
pop CC
CC
M
M
reg, CC
H
I
N
Z
N
Z
0
H
C
0
I
N
Z
N
Z
N
Z
C
C
PUSH
Push onto the Stack
push Y
RCF
Reset carry flag
C=0
RET
Subroutine Return
RIM
Enable Interrupts
I=0
RLC
Rotate left true C
C <= Dst <= C
reg, M
N
Z
C
RRC
Rotate right true C
C => Dst => C
reg, M
N
Z
C
RSP
Reset Stack Pointer
S = Max allowed
SBC
Subtract with Carry
A=A-M-C
N
Z
C
SCF
Set carry flag
C=1
SIM
Disable Interrupts
I=1
SLA
Shift left Arithmetic
C <= Dst <= 0
reg, M
N
Z
C
SLL
Shift left Logic
C <= Dst <= 0
reg, M
N
Z
C
SRL
Shift right Logic
0 => Dst => C
reg, M
0
Z
C
SRA
Shift right Arithmetic
Dst7 => Dst => C
reg, M
N
Z
C
SUB
Subtraction
A=A-M
A
N
Z
C
SWAP
SWAP nibbles
Dst[7..4] <=> Dst[3..0] reg, M
N
Z
TNZ
Test for Neg & Zero
tnz lbl1
N
Z
TRAP
S/W trap
S/W interrupt
WFI
Wait for Interrupt
XOR
Exclusive OR
N
Z
0
0
A
M
1
1
M
1
0
A = A XOR M
A
M
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ST72E121 ST72T121
7 ELECTRICAL CHARACTERISTICS
7.1 ABSOLUTE MAXIMUM RATINGS
This product contains devices to protect the inputs
against damage due to high static voltages, however it is advisable to take normal precaution to
avoid application of any voltage higher than the
specified maximum rated voltages.
For proper operation it is recommended that VI
and VO be higher than V SS and lower than V DD.
Reliability is enhanced if unused inputs are connected to an appropriate logic voltage level (VDD
or V SS).
Symbol
Parameter
VDD
Digital Supply Voltage
VDDA
Analog Supply and Reference Voltage
Power Considerations.The average chip-junction temperature, TJ, in Celsius can be obtained
from:
TJ=
TA + PD x RthJA
Where: TA =
Ambient Temperature.
RthJA = Package thermal resistance
(junction-to ambient).
PINT + PPORT.
PD =
PINT = IDD x VDD (chip internal power).
PPORT =Port power dissipation
determined by the user)
Value
Unit
-0.3 to 6.0
V
VDD - 0.3 to VDD + 0.3
V
Input Voltage
VSS - 0.3 to VDD + 0.3
V
VAI
Analog Input Voltage (A/D Converter)
VSS - 0.3 to VDD + 0.3
VSSA-0.3 to VDDA+0.3
V
VO
Output Voltage
VI
VSS - 0.3 to VDD + 0.3
V
IVDD
Total Current into VDD (source)
100
mA
IVSS
Total Current out of VSS (sink)
Junction Temperature
100
mA
150
°C
-60 to 150
°C
TJ
TSTG
Storage Temperature
Note: Stresses above those listed as “absolute maximum ratings” may cause permanent damage to the device. This is
a stress rating only and functional operation of the device at these conditions is not implied. Exposure to maximum
rating conditions for extended periods may affect device reliability.
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ST72E121 ST72T121
7.2 RECOMMENDED OPERATING CONDITIONS
Symbol
Parameter
Operating Temperature
TA
Value
Test Conditions
Min.
Typ.
Max.
Unit
1 Suffix Version
0
6 Suffix Version
-40
85
°C
3 Suffix Version
-40
125
°C
3.51)
3.0
5.5
5.5
V
02)
02)
8
16
MHz
VDD
Operating Supply Voltage
fOSC = 16 MHz (1 & 6 Suffix)
fOSC = 8 MHz
fOSC
Oscillator Frequency
VDD = 3.0V
VDD = 3.5V (1 & 6 Suffix)
70
°C
Note
1) A safe reset (with Low Voltage Detector option) is not guaranteed at 16 MHz.
2) A/D operation and Oscillator start-up are not guaranteed below 1MHz.
Figure 41. Maximum Operating Frequency (fOSC) Versus Supply Voltage (VDD)
FUNCTIONALITY NOT GUARANTEED IN THIS AREA
FUNCTIONALITY NOT GUARANTEED IN THIS AREA
fOSC
FUNCTIONALITY GUARANTEED IN THIS AREA
FOR TEMPERATURE HIGHER THAN 85°C
[MHz]
16
8
4
Supplly Voltage
[V]
1
0
2.5
3
3.5
4
4.5
5
5.5
6
FUNCTIONALITY NOT GUARANTEED IN THIS AREA WITH RESONATOR
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ST72E121 ST72T121
7.3 DC ELECTRICAL CHARACTERISTICS
(TA = -40°C to +125°C and VDD = 5V unless otherwise specified)
Symbol
VIL
VIH
VHYS
VOL
VOH
IIL
IIH
IIH
RON
RPU
IDD
Parameter
Input Low Level Voltage
All Input pins
Input High Level Voltage
All Input pins
Hysteresis Voltage 1)
All Input pins
Low Level Output Voltage
All Output pins
Test Conditions
Value
Min.
Typ.
3V < VDD < 5.5V
3V < VDD < 5.5V
IOL = +10µA
IOL = + 2mA
IOL = +10µA
Low Level Output Voltage IOL = +10mA
IOL = + 15mA
High Sink I/O pins
IOL = + 20mA, TA = 85°C max
High Level Output Voltage IOH = - 10µA
All Output pins
IOH= - 2mA
Input Leakage Current
VIN = VSS (No Pull-up configured)
All Input pins but RESET 4) VIN = VDD
Input Leakage Current
VIN = VDD
RESET pin
VIN > VIH
Reset Weak Pull-up RON
VIN < VIL
I/O Weak Pull-up RPU
VIN < VIL
fOSC = 4 MHz, fCPU = 2 MHz
Supply Current in
fOSC = 8 MHz, fCPU = 4 MHz
2)
RUN Mode
fOSC = 16 MHz, fCPU = 8 MHz
fOSC = 4 MHz, fCPU= 125 kHz
Supply Current in SLOW
fOSC = 8 MHz, fCPU= 250 kHz
Mode 2)
fOSC = 16 MHz, fCPU= 500 kHz
fOSC = 4MHz, fCPU = 2MHz
Supply Current in WAIT
fOSC = 8MHz, fCPU = 4 MHz
Mode 3)
fOSC = 16MHz, fCPU = 8 MHz
fOSC = 4 MHz, fCPU= 125 kHz
Supply Current in WAITfOSC = 8 MHz, fCPU= 250 kHz
5)
MINIMUM Mode
fOSC = 16 MHz, fCPU= 500 kHz
ILOAD = 0mA without LVD, TA = 85°C max
Supply Current in HALT
ILOAD = 0mA without LVD
Mode
ILOAD = 0mA with LVD
Max.
VDD x 0.3
VDD x 0.7
V
V
400
mV
0.1
0.4
0.1
1.5
3.0
3.0
4.9
4.2
20
60
Unit
V
V
0.1
1.0
0.1
1.0
40
120
100
3.5
6
11
1.5
2.5
4.5
2
4
6.5
0.8
1
1.6
1
5
70
80
240
µA
kΩ
kΩ
7
12
20
3
5
9
4
8
12
1.5
2
3.5
10
20
100
mA
mA
mA
mA
µA
Notes:
1. Hysteresis voltage between switching levels. Based on characterisation results, not tested.
2. CPU running with memory access, no DC load or activity on I/O’s; clock input (OSCIN) driven by external square wave.
3. No DC load or activity on I/O’s; clock input (OSCIN) driven by external square wave.
4. Except OSCIN and OSCOUT
5. WAIT Mode with SLOW Mode selected. Based on characterisation results, not tested.
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ST72E121 ST72T121
7.4 RESET CHARACTERISTICS
(TA=-40...+125oC and V DD=5V±10% unless otherwise specified.
Symbol
RON
tRESET
tPULSE
Parameter
Conditions
VIN > VIH
VIN < VIL
Reset Weak Pull-up RON
Pulse duration generated by watchdog and POR reset
Minimum pulse duration to be applied on external RESET pin
Min
Typ 1)
Max
Unit
20
60
40
120
80
240
kΩ
µs
1
10 1)
ns
Note:
1) These values given only as design guidelines and are not tested.
7.5 OSCILLATOR CHARACTERISTICS
(TA = -40°C to +125°C unless otherwise specified)
Symbol
Parameter
gm
fOSC
tstart
Oscillator transconductance
Crystal frequency
Osc. start up time
Test Conditions
Value
Typ.
Min.
2
1
VDD = 5V±10%
Max.
9
16
50
Unit
mA/V
MHz
ms
7.6 PERIPHERAL CHARACTERISTICS
Low Voltage Detection Reset Electrical Specifications (Option)
Symbol
Parameter
VLVDUP
LVD Reset Trigger, VDD rising edge
VLVDDOWN
LVD Reset Trigger, VDD falling edge
VLVDHYS
LVD Reset Trigger, hysteresis2)
Conditions
fOSC = 8 MHz max1).
Min.
Typ.
Max.
Unit
3.6 2
3.85
4.1
V
3.6
3.85
3.35
250
V
mV
Notes:
1. The safe reset cannot be guaranted by the LVD when fosc is greater than 8MHz.
2. Based on characterisation results, not tested.
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85
ST72E121 ST72T121
PERIPHERAL CHARACTERISTICS (Cont’d)
Serial Peripheral Interface
Value
Ref.
Symbol
Parameter
Condition
Unit
Min.
Max.
1/4
1/2
fSPI
SPI frequency
Master
Slave
1/128
dc
1
tSPI
SPI clock periode
Master
Slave
4
2
2
tLead
Enable lead time
Slave
120
ns
3
tLag
Enable lag time
Slave
120
ns
4
tSPI_H
Clock (SCK) high time
Master
Slave
100
90
ns
5
tSPI_L
Clock (SCK) low time
Master
Slave
100
90
ns
6
tSU
Data set-up time
Master
Slave
100
100
ns
7
tH
Data hold time (inputs)
Master
Slave
100
100
ns
8
tA
Access time (time to data active
from high impedance state)
9
tDis
10
tV
11
0
Disable time (hold time to high impedance state)
tCPU
120
ns
240
ns
120
tCPU
ns
Slave
Data valid
Master (before capture edge)
Slave (after enable edge)
0.25
tHold
Data hold time (outputs)
Master (before capture edge)
Slave (after enable edge)
0.25
0
12
tRise
Rise time
Outputs: SCK,MOSI,MISO
(20% VDD to 70% VDD, CL = 200pF) Inputs: SCK,MOSI,MISO,SS
100
100
ns
µs
13
tFall
Fall time
Outputs: SCK,MOSI,MISO
(70% VDD to 20% VDD, CL = 200pF) Inputs: SCK,MOSI,MISO,SS
100
100
ns
µs
tCPU
ns
Measurement points are V OL, VOH, VIL and VIH in the SPI Timing Diagram
Figure 42. SPI Master Timing Diagram CPHA=0, CPOL=0
SS
(INPUT)
1
SCK
(OUTPUT)
4
MISO
(INPUT)
MOSI
(OUTPUT)
6
10
D7-IN
7
D7-OUT
11
13
12
5
D6-IN
D6-OUT
D0-IN
D0-OUT
VR000109
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86
fCPU
ST72E121 ST72T121
PERIPHERAL CHARACTERISTICS (Cont’d)
Measurement points are V OL, VOH, VIL and VIH in the SPI Timing Diagram
Figure 43. SPI Master Timing Diagram CPHA=0, CPOL=1
SS
(INPUT)
1
13
SCK
(OUTPUT)
5
MISO
(INPUT)
6
MOSI
(OUTPUT)
10
12
4
D7-IN
7
D6-IN
D7-OUT
11
D0-IN
D6-OUT
D0-OUT
VR000110
Figure 44. SPI Master Timing Diagram CPHA=1, CPOL=0
SS
(INPUT)
1
13
SCK
(OUTPUT)
4
MISO
(INPUT)
5
D7-OUT
6
MOSI
(OUTPUT)
12
10
D6-OUT
D0-OUT
7
D6-IN
D7-IN
11
D0-IN
VR000107
Figure 45. SPI Master Timing Diagram CPHA=1, CPOL=1
SS
(INPUT)
1
12
SCK
(OUTPUT)
MISO
(INPUT)
MOSI
(OUTPUT)
13
4
5
6
10
D7-IN
7
D7-OUT
11
D6-IN
D6-OUT
D0-IN
D0-OUT
VR000108
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87
ST72E121 ST72T121
PERIPHERAL CHARACTERISTICS (Cont’d)
Measurement points are V OL, VOH, VIL and VIH in the SPI Timing Diagram
Figure 46. SPI Slave Timing Diagram CPHA=0, CPOL=0
SS
(INPUT)
2
1
4
MISO HIGH-Z
(OUTPUT)
8
MOSI
(INPUT)
3
12
13
SCK
(INPUT)
5
D7-OUT
D6-OUT
10
D0-OUT
11
D7-IN
9
D6-IN
D0-IN
7
6
VR000113
Figure 47. SPI Slave Timing Diagram CPHA=0, CPOL=1
SS
(INPUT)
2
1
13
12
SCK
(INPUT)
4
5
HIGH-Z
MISO
(OUTPUT)
8
MOSI
(INPUT)
3
D7-OUT
D6-OUT
10
D0-OUT
11
D7-IN
9
D6-IN
D0-IN
7
6
VR000114
Figure 48. SPI Slave Timing Diagram CPHA=1, CPOL=0
SS
(INPUT)
2
SCK
(INPUT)
HIGH-Z
MISO
(OUTPUT)
1
4
13
3
5
D7-OUT
D6-OUT
8
D7-IN
D0-OUT
9
11
10
MOSI
(INPUT)
12
D6-IN
D0-IN
7
6
VR000111
Figure 49. SPI Slave Timing Diagram CPHA=1, CPOL=1
SS
(INPUT)
2
SCK
(INPUT)
HIGH-Z
MISO
(OUTPUT)
MOSI
(INPUT)
1
5
12
3
4
D7-OUT
8
D6-OUT
D7-IN
D0-OUT
11
10
6
13
D6-IN
9
D0-IN
7
VR000112
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ST72E121 ST72T121
8 GENERAL INFORMATION
8.1 EPROM ERASURE
EPROM version devices are erased by exposure
to high intensity UV light admitted through the
transparent window. This exposure discharges the
floating gate to its initial state through induced
photo current.
It is recommended that the EPROM devices be
kept out of direct sunlight, since the UV content of
sunlight can be sufficient to cause functional failure. Extended exposure to room level fluorescent
lighting may also cause erasure.
An opaque coating (paint, tape, label, etc...)
should be placed over the package window if the
product is to be operated under these lighting conditions. Covering the window also reduces IDD in
power-saving modes due to photo-diode leakage
currents.
An Ultraviolet source of wave length 2537 Å yielding a total integrated dosage of 15 Watt-sec/cm2 is
required to erase the device. It will be erased in 15
to 20 minutes if such a UV lamp with a 12mW/cm2
power rating is placed 1 inch from the device window without any interposed filters.
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ST72E121 ST72T121
8.2 PACKAGE MECHANICAL DATA
Figure 50. 42-Pin Plastic Dual In-Line Package, Shrink 600-mil Width
Dim.
E
mm
Min
Typ
A
A2
A1
b2
b
D
e
A
L
c
E1
eA
eB
E
0.015
GAGE PLANE
eC
inches
Max
Min
Typ
5.08
Max
0.200
A1
0.51
0.020
A2
3.05
3.81 4.57 0.120 0.150 0.180
b
0.38
0.46 0.56 0.015 0.018 0.022
b2
0.89
1.02 1.14 0.035 0.040 0.045
c
0.23
0.25 0.38 0.009 0.010 0.015
D
36.58 36.83 37.08 1.440 1.450 1.460
E
15.24
E1
12.70 13.72 14.48 0.500 0.540 0.570
16.00 0.600
0.630
e
1.78
0.070
eA
15.24
0.600
eB
18.54
0.730
1.52 0.000
0.060
eB
eC
L
2.54
3.30 3.56 0.100 0.130 0.140
Number of Pins
N
42
Figure 51. 42-Pin Shrink Ceramic Dual In-Line Package, 600-mil Width
Dim.
mm
Min
Typ
A
Min
Typ
4.01
0.76
0.030
B
0.38
0.46 0.56 0.015 0.018 0.022
B1
0.76
0.89 1.02 0.030 0.035 0.040
C
0.23
0.25 0.38 0.009 0.010 0.015
D
36.68 37.34 38.00 1.444 1.470 1.496
E1
35.56
1.400
14.48 14.99 15.49 0.570 0.590 0.610
e
1.78
0.070
G
14.12 14.38 14.63 0.556 0.566 0.576
G1
18.69 18.95 19.20 0.736 0.746 0.756
G2
1.14
0.045
G3
11.05 11.30 11.56 0.435 0.445 0.455
G4
15.11 15.37 15.62 0.595 0.605 0.615
L
S
2.92
5.08 0.115
0.89
0.200
0.035
Number of Pins
N
90/93
Max
0.158
A1
D1
CDIP42SW
inches
Max
42
ST72E121 ST72T121
Figure 52. 44-Pin Thin Quad Flat Package
Dim.
A
A2
D
D1
b
e
c
L1
L
Typ
A
A1
E1 E
mm
Min
inches
Max
Min
Typ
Max
1.60
0.063
0.15 0.002
0.006
A1
0.05
A2
1.35
1.40 1.45 0.053 0.055 0.057
b
0.30
0.37 0.45 0.012 0.015 0.018
C
0.09
0.20 0.004 0.000 0.008
D
12.00
0.472
D1
10.00
0.394
E
12.00
0.472
E1
10.00
0.394
e
0.80
θ
0°
L
0.45
L1
h
3.5°
0.031
7°
0°
3.5°
7°
0.60 0.75 0.018 0.024 0.030
1.00
0.039
Number of Pins
N
44
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ST72E121 ST72T121
8.3 ORDERING INFORMATION
Each device is available for production in user programmable version (OTP). OTP devices are
shipped to customer with a default blank content
FFh. There is one common EPROM version for
debugging and prototyping which features the
maximum memory size and peripherals of the
family. Care must be taken to only use resources
available on the target device.
Figure 53. OTP User Programmable Device Types
DEVICE PACKAGE
TEMP.
RANGE
X
S= LVD Reset option
3 = automotive -40 to +125°C
6= industrial -40 to +85 °C
B= Plastic DIP
T= Plastic TQFP
ST72T121J2
ST72T121J4
Notes:
– The ST72E121J4D0 (CERDIP 25 °C) is used as the EPROM versions for the above devices.
– The ROM versions are supported by the ST72124 family.
Note: ROM versions are supported by the ST72334/124 family. Important product differences must be taken into account. Refer to the Preamble in the ST72334/124 Datasheet for more information.
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ST72E121 ST72T121
9 SUMMARY OF CHANGES
Change Description (Rev. 1.5 to 1.6)
Page
Added new External Connections section
Removed RP external resistor
Changed ORed to ANDed in External interrupts paragraph, to read “If several input pins, connected to the same interrupt vector, are configured as interrupts, their signals are logically ANDed before entering the edge/level detection block”.
Added note ”Any modification of one of these two bits resets the interrupt request related to
this interrupt vector.”
Added clamping diodes to I/O pin figure and table
Added sections on low power modes and interrupts to peripheral descriptions
Changed 16-bit Timer chapter
Added details to description of FOLV1 and FOLV2 bits
Added Reset characteristics section
Added min. value for VLVDUP
Removed ST72121 ROM device (supported by ST72124)
7
15
18 and 24
23
26
31, 44, 57, 71
33 to 49
45
84
84
Change Description (Rev. 1.6 to 1.7)
SPR2 bit reinstated in SPI chapter
62 to 74
Change Description (Rev. 1.7 to 1.8) of 24 Nov 2000
Note on page 1 and Note on page 92 added to document.
1, 92
Change Description (Rev. 1.8 to 1.9) of 31 May 2001
SPI frequency changed from fCPU/2 to fCPU/4 in Table 17.
73
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of use of such information nor for any infringement of patents or other rights of third parties which may result from its use. No license is granted
by implication or otherwise under any patent or patent rights of STMicroelectronics. Specifications mentioned in this publication are subject
to change without notice. This publication supersedes and replaces all information previously supplied. STMicroelectronics products are not
authorized for use as critical components in life support devices or systems without the express written approval of STMicroelectronics.
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2001 STMicroelectronics - All Rights Reserved.
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I2C system is granted provided that the system conforms to the I2C Standard Specification as defined by Philips.
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