ATMEL T89C51AC2-RLTC-M

T89C51AC2
8-bit MCU with 32K bytes Flash, 10 bits A/D and EEPROM
1. Description
The T89C51AC2 is a high performance CMOS FLASH
version of the 80C51 CMOS single chip 8-bit
microcontrollers. It contains a 32Kbytes Flash memory
block for program and data.
The fully static design of the T89C51AC2 allows to
reduce system power consumption by bringing the clock
frequency down to any value, even DC, without loss of
data.
The 16K bytes or 32K bytes FLASH memory can be
programmed either in parallel mode or in serial mode
with the ISP capability or with software. The
programming voltage is internally generated from the
standard VCC pin.
The T89C51AC2 has 2 software-selectable modes of
reduced activity and 8 bit clock prescaler for further
reduction in power consumption. In the Idle mode the
CPU is frozen while the peripherals and the interrupt
system are still operating. In the power-down mode the
RAM is saved and all other functions are inoperative.
The T89C51AC2 retains all features of the 80C52 with
256 bytes of internal RAM, a 7-source 4-level interrupt
controller and three timer/counters.
In addition, the T89C51AC2 has a 10 bits A/D converter,
a 2Kbytes Boot Flash Memory, 2 Kbytes EEPROM
for data, a Programmable Counter Array, an XRAM of
1024 byte, a Hardware Watchdog Timer and a more
versatile serial channel that facilitates multiprocessor
communication (EUART).
The added features of the T89C51AC2 make it more
powerful for applications that need A/D conversion,
pulse width modulation, high speed I/O and counting
capabilities such as industrial control, consumer goods,
alarms, motor control, ...
While remaining fully compatible with the 80C51 it
offers a superset of this standard microcontroller. In X2
mode a maximum external clock rate of 20 MHz reaches
a 300 ns cycle time.
2. Features
• 80C51 core architecture:
•
•
•
•
•
•
•
•
•
256 bytes of on-chip RAM
1Kbytes of on-chip XRAM
32 Kbytes of on-chip Flash memory
2 Kbytes of on-chip Flash for Bootloader
2 Kbytes of on-chip EEPROM
14-source 4-level interrupt
Three 16-bit timer/counter
Full duplex UART compatible 80C51
maximum crystal frequency 40 MHz. In X2 mode,
20 MHz (CPU core, 40 MHz)
• Five ports: 32 + 2 digital I/O lines
• Five channel 16-bit PCA with:
- PWM (8-bit)
- High-speed output
- Timer and edge capture
• Double Data Pointer
• 21 bit watchdog timer (including 7 programmable
bits)
• A 10-bit resolution analog to digital converter (ADC)
with 8 multiplexed inputs
• 20 microsecond conversion time
• Two conversion modes
On-chip emulation Logic (enhanced Hook system)
•
• Power saving modes:
• Idle mode
• Power down mode
Power supply: 5V +/- 10% (or 3V** +/- 10%)
•
• Temperature range: Industrial (-40 to +85C)
• Packages: TQFP44, PLCC44
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T89C51AC2
T2
T2EX
PCA
ECI
Vss
Vcc
TxD
RxD
3. Block Diagram
XTAL1
RAM
256x8
UART
XTAL2
ALE
C51
CORE
PSEN
Flash
32kx
8
ERAM
Boot
EE
1kx8
loader PROM
2kx8
2kx8
PCA
Timer2
IB-bus
CPU
EA
Timer 0
Timer 1
RD
INT
Ctrl
Parallel I/O Ports & Ext. Bus
Watch
Dog
10 bit
ADC
P4(2)
P3
P2
P1(1)
INT1
INT0
T1
T0
RESET
WR
P0
Port 0 Port 1 Port 2 Port 3 Port 4
Emul
Unit
(1): 8 analog Inputs / 8 Digital I/O
(2): 2-Bit I/O Port
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T89C51AC2
6
5
4
3
2
1
44
43
42
41
40
P1.3 / AN3 / CEX0
P1.2 / AN2 / ECI
P1.1 / AN1 / T2EX
P1.0 / AN 0 / T2
VAREF
VAGND
RESET
VSS
VCC
XTAL1
XTAL2
4. Pin Configuration
7
8
9
10
11
12
13
14
15
16
17
39
38
37
36
35
34
33
32
31
30
29
PLCC44
ALE
PSEN
P0.7 / AD7
P0.6 / AD6
P0.5 / AD5
P0.4 / AD4
P0.3 / AD3
P0.2 / AD2
P0.1 / AD1
P0.0 / AD0
P2.0 / A8
P1.3 / AN3 / CEX0
P1.2 / AN2 / ECI
P1.1 / AN1 / T2EX
P1.0 / AN 0 / T2
VAREF
VAGND
RESET
VSS
VCC
XTAL1
XTAL2
P3.6 / WR
P3.7 / RD
P4.0
P4.1
P2.7 / A15
P2.6 / A14
P2.5 / A13
P2.4 / A12
P2.3 / A11
P2.2 / A10
P2.1 / A9
18
19
20
21
22
23
24
25
26
27
28
P1.4 / AN4 / CEX1
P1.5 / AN5 / CEX2
P1.6 / AN6 / CEX3
P1.7 / AN7 / CEX4
EA
P3.0 / RxD
P3.1 / TxD
P3.2 / INT0
P3.3 / INT1
P3.4 / T0
P3.5 / T1
44 43 42 41 40 39 38 37 36 35 34
P1.4 / AN4 / CEX1
P1.5 / AN5 / CEX2
P1.6 / AN6 / CEX3
P1.7 / AN7 / CEX4
EA
P3.0 / RxD
P3.1 / TxD
P3.2 / INT0
P3.3 / INT1
P3.4 / T0
P3.5 / T1
2
33
32
3
4
30
1
5
6
7
8
31
TQFP44
29
28
27
9
26
25
10
24
23
11
ALE
PSEN
P0.7 / AD7
P0.6 / AD6
P0.5 / AD5
P0.4 /AD4
P0.3 /AD3
P0.2 /AD2
P0.1 /AD1
P0.0 /AD0
P2.0 / A8
P3.6 / WR
P3.7 / RD
P4.0
P4.1
P2.7 / A15
P2.6 / A14
P2.5 / A13
P2.4 / A12
P2.3 / A11
P2.2 / A10
P2.1 / A9
1213 14 15 16 17 18 19 20 2122
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T89C51AC2
Table 1. Pin Description
Pin Name
Type
VSS
GND
VCC
Description
Circuit ground potential.
Supply voltage during normal, idle, and power-down operation.
VAREF
Reference Voltage for ADC
VAGND
Reference Ground for ADC
P0.0:7
I/O
Port 0:
is an 8-bit open drain bi-directional I/O port. Port 0 pins that have 1’s written to them float, and in this
state can be used as high-impedance inputs. Port 0 is also the multiplexed low-order address and data
bus during accesses to external Program and Data Memory. In this application it uses strong internal pullups when emitting 1’s.
Port 0 also outputs the code bytes during program validation. External pull-ups are required during
program verification.
In the T89C51AC2 Port 0 can sink or source 5mA. It can drive CMOS inputs without external pull-ups.
Port 1:
is an 8-bit bi-directional I/O port with internal pull-ups. Port 1 pins can be used for digital input/output
or as analog inputs for the Analog Digital Converter (ADC). Port 1 pins that have 1’s written to them
are pulled high by the internal pull-up transistors and can be used as inputs in this state. As inputs, Port
1 pins that are being pulled low externally will be the source of current (IIL, on the datasheet) because
of the internal pull-ups. Port 1 pins are assigned to be used as analog inputs via the ADCCF register.
As a secondary digital function, port 1 contains the Timer 2 external trigger and clock input; the PCA
external clock input and the PCA module I/O.
P1.0:7
I/O
P1.0 / AN0 / T2
Analog input channel 0,
External clock input for Timer/counter2.
P1.1 / AN1 / T2EX
Analog input channel 1,
Trigger input for Timer/counter2.
P1.2 / AN2 / ECI
Analog input channel 2,
PCA external clock input.
P1.3 / AN3 / CEX0
Analog input channel 3,
PCA module 0 Entry of input/PWM output.
P1.4 / AN4 / CEX1
Analog input channel 4,
PCA module 1 Entry of input/PWM output.
P1.5 / AN5 / CEX2
Analog input channel 5,
PCA module 2 Entry of input/PWM output.
P1.6 / AN6 / CEX3
Analog input channel 6,
PCA module 3 Entry of input/PWM output.
P1.7 / AN7 / CEX4
Analog input channel 7,
PCA module 4 Entry ot input/PWM output.
Port 1 receives the low-order address byte during EPROM programming and program verification. In the
T89C51AC2 Port 1 can sink or source 5mA. It can drive CMOS inputs without external pull-ups.
P2.0:7
I/O
Port 2:
Is an 8-bit bi-directional I/O port with internal pull-ups. Port 2 pins that have 1’s written to them are
pulled high by the internal pull-ups and can be used as inputs in this state. As inputs, Port 2 pins that
are being pulled low externally will be a source of current (IIL, on the datasheet) because of the internal
pull-ups. Port 2 emits the high-order address byte during accesses to the external Program Memory and
during accesses to external Data Memory that uses 16-bit addresses (MOVX @DPTR). In this application,
it uses strong internal pullups when emitting 1’s. During accesses to external Data Memory that use 8 bit
addresses (MOVX @Ri), Port 2 transmits the contents of the P2 special function register.
It also receives high-order addresses and control signals during program validation.
In the T89C51AC2 Port 2 can sink or source 5mA. It can drive CMOS inputs without external pull-ups.
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T89C51AC2
Pin Name
Type
Description
Port 3:
Is an 8-bit bi-directional I/O port with internal pull-ups. Port 3 pins that have 1’s written to them are
pulled high by the internal pull-up transistors and can be used as inputs in this state. As inputs, Port 3
pins that are being pulled low externally will be a source of current (IIL, on the datasheet) because of the
internal pull-ups.
The output latch corresponding to a secondary function must be programmed to one for that function to
operate (except for TxD and WR). The secondary functions are assigned to the pins of port 3 as follows:
P3.0:7
P4.0:1
I/O
I/O
P3.0 / RxD:
Receiver data input (asynchronous) or data input/output (synchronous) of the serial interface
P3.1 / TxD:
Transmitter data output (asynchronous) or clock output (synchronous) of the serial interface
P3.2 / INT0:
External interrupt 0 input / timer 0 gate control input
P3.3 / INT1:
External interrupt 1 input / timer 1 gate control input
P3.4 / T0:
Timer 0 counter input
P3.5 / T1:
Timer 1 counter input
P3.6 / WR:
External Data Memory write strobe; latches the data byte from port 0 into the external data memory
P3.7 / RD:
External Data Memory read strobe; Enables the external data memory.
In the T89C51AC2 Port 3 can sink or source 5mA. It can drive CMOS inputs without external pull-ups.
Port 4:
Is an 2-bit bi-directional I/O port with internal pull-ups. Port 4 pins that have 1’s written to them are
pulled high by the internal pull-ups and can be used as inputs in this state. As inputs, Port 4 pins that are
being pulled low externally will be a source of current (IIL, on the datasheet) because of the internal pullup transistor.
In the T89C51AC2 Port 3 can sink or source 5mA. It can drive CMOS inputs without external pull-ups.
RESET
ALE
PSEN
I/O
Reset:
A high level on this pin during two machine cycles while the oscillator is running resets the device. An
internal pull-down resistor to VSS permits power-on reset using only an external capacitor to VCC.
O
ALE:
An Address Latch Enable output for latching the low byte of the address during accesses to the external
memory. The ALE is activated every 1/6 oscillator periods (1/3 in X2 mode) except during an external
data memory access. When instructions are executed from an internal FLASH (EA = 1), ALE generation
can be disabled by the software.
O
PSEN:
The Program Store Enable output is a control signal that enables the external program memory of the bus
during external fetch operations. It is activated twice each machine cycle during fetches from the external
program memory. (However, when executing outside of the external program memory two activations of
PSEN are skipped during each access to the external Data memory). The PSEN is not activated during
fetches from the internal data memory.
EA:
EA
I
When External Access is held at the high level, instructions are fetched from the internal FLASH when
the program counter is less then 8000H. When held at the low level, CANARY fetches all instructions
from the external program memory.
XTAL1
I
XTAL1:
Input of the inverting oscillator amplifier and input of the internal clock generator circuits.
To drive the device from an external clock source, XTAL1 should be driven, while XTAL2 is left
unconnected. To operate above a frequency of 16 MHz, a duty cycle of 50% should be maintained.
XTAL2
O
XTAL2:
Output from the inverting oscillator amplifier.
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T89C51AC2
4.1. I/O Configurations
Each Port SFR operates via type-D latches, as illustrated in Figure 1 for Ports 3 and 4. A CPU "write to latch"
signal initiates transfer of internal bus data into the type-D latch. A CPU "read latch" signal transfers the latched
Q uotput onto the internal bus. Similarly, a "read pin" signal transfers the logical level of the Port pin. Some Port
data instructions activate the "read latch" signal while others activate the "read pin" signal. Latch instructions are
referred to as Read-Modify-Write instructions. Each I/O line may be independently programmed as input or output.
4.2. Port 1, Port 3 and Port 4
Figure 1 shows the structure of Ports 1 and 3, which have internal pull-ups. An external source can pull the pin
low. Each Port pin can be configured either forgeneral-purpose I/O or for its alternate input output function.
To use a pin for general-purpose output, set or clear the corresponding bit in the Px register (x=1,3 or 4). To use
a pin for general purpose input, set the bit in the Px register. This turns off the output FET drive.
To configure a pin for its alternate function, set the bit in the Px register. When the latch is set, the "alternate
output function" signal controls the output level (see Figure 1). The operation of Ports 1, 3 and 4 is discussed
further in "quasi-Bidirectional Port Operation" paragraph.
VCC
ALTERNATE
OUTPUT
FUNCTION
READ
LATCH
INTERNAL
BUS
WRITE
TO
LATCH
READ
PIN
INTERNAL
PULL-UP (1)
P1.x
P3.x
P4.x
D P1.X Q
P3.X
P4.X
LATCH
CL
ALTERNATE
INPUT
FUNCTION
NOTE:
1. The internal pull-up can be disabled on P1 when analog function is selected.
Figure 1. Port 1, Port 3 and Port 4 Structure
4.3. Port 0 and Port2
Ports 0 and 2 are used for general-purpose I/O or as the external address/data bus. Port 0, shown in Figure 2,
differs from the other Ports in not having internal pull-ups. Figure 3 shows the structure of Port 2. An external
source can pull a Port 2 pin low.
To use a pin for general-purpose output, set or clear the corresponding bit in the Px register (x=0 or 2). To use
a pin for general purpose input, set the bit in the Px register to turn off the output driver FET.
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T89C51AC2
ADDRESS LOW/ CONTROL
DATA
VDD
(2)
READ
LATCH
P0.x (1)
1
INTERNAL
BUS
WRITE
TO
LATCH
D
Q
P0.X
LATCH
0
READ
PIN
NOTE:
1. Port 0 is precluded from use as general purpose I/O Ports when used as address/data bus drivers.
2. Port 0 internal strong pull-ups assist the logic-one output for memory bus cycles only. Except for these bus cycles, the pull-up FET is off,
Port 0 outputs are open-drain.
Figure 2. Port 0 Structure
ADDRESS HIGH/ CONTROL
DATA
VDD
INTERNAL
PULL-UP (2)
READ
LATCH
P2.x (1)
1
INTERNAL
BUS
WRITE
TO
LATCH
D
Q
P2.X
LATCH
0
READ
PIN
NOTE:
1. Port 2 is precluded from use as general purpose I/O Ports when as address/data bus drivers.
2. Port 2 internal strong pull-ups FET (P1 in FiGURE) assist the logic-one output for memory bus cyle.
Figure 3. Port 2 Structure
When Port 0 and Port 2 are used for an external memory cycle, an internal control signal switches the outputdriver input from the latch output to the internal address/data line.
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T89C51AC2
4.4. Read-Modify-Write Instructions
Some instructions read the latch data rather than the pin data. The latch based instructions read the data, modify
the data and then rewrite the latch. These are called "Read-Modifiy-Write" instructions. Below is a complete list
of these special instructions (see Table 2). When the destination operand is a Port or a Port bit, these instructions
read the latch rather than the pin:
Table 2. Read-Modify-Write Instructions
Instruction
Description
Example
ANL
logical AND
ANL P1, A
ORL
logical OR
ORL P2, A
XRL
logical EX-OR
XRL P3, A
JBC
jump if bit = 1 and clear bit
JBC P1.1, LABEL
CPL
complement bit
CPL P3.0
INC
increment
INC P2
DEC
decrement
DEC P2
DJNZ
decrement and jump if not zero
DJNZ P3, LABEL
MOV Px.y, C
move carry bit to bit y of Port x
MOV P1.5, C
CLR Px.y
clear bit y of Port x
CLR P2.4
SET Px.y
set bit y of Port x
SET P3.3
It is not obvious the last three instructions in this list are Read-Modify-Write instructions. These instructions read
the port (all 8 bits), modify the specifically addressed bit and write the new byte back to the latch. These ReadModify-Write instructions are directed to the latch rather than the pin in order to avoid possible misinterpretation
of voltage (and therefore, logic)levels at the pin. For example, a Port bit used to drive the base of an external
bipolar transistor can not rise above the transistor’s base-emitter junction voltage (a value lower than VIL). With
a logic one written to the bit, attemps by the CPU to read the Port at the pin are misinterpreted as logic zero. A
read of the latch rather than the pins returns the correct logic-one value.
4.5. Quasi-Bidirectional Port Operation
Port 1, Port 2, Port 3 and Port 4 have fixed internal pull-ups and are referred to as "quasi-bidirectional" Ports.
When configured as an input, the pin impedance appears as logic one and sources current in response to an external
logic zero condition. Port 0 is a "true bidirectional" pin. The pins float when configured as input. Resets write
logic one to all Port latches. If logical zero is subsequently written to a Port latch, it can be returned to input
condions by a logical one written to the latch.
NOTE:
Port latch values change near the end of Read-Modify-Write insruction cycles. Output buffers (and therefore the pin state) update early in the
instruction after Read-Modify-Write instruction cycle.
Logical zero-to-one transitions in Port 1, Port 2, Port 3 and Port 4 use an additional pull-up (p1) to aid this logic
transition (see Figure 4.). This increases switch speed. This extra pull-up sources 100 times normal internal circuit
current during 2 oscillator clock periods. The internal pull-ups are field-effect transistors rather than linear resistors.
Pull-ups consist of three p-channel FET (pFET) devices. A pFET is on when the gate senses logical zero and off
when the gate senses logical one. pFET #1 is turned on for two oscillator periods immediately after a zero-to-one
transition in the Port latch. A logical one at the Port pin turns on pFET #3 (a weak pull-up) through the inverter.
This inverter and pFET pair form a latch to drive logical one. pFET #2 is a very weak pull-up switched on
whenever the associated nFET is switched off. This is traditional CMOS switch convention. Current strengths are
1/10 that of pFET #3.
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T89C51AC2
2 Osc. PERIODS
VCC
VCC
VCC
p1(1)
p2
p3
P1.x
P2.x
P3.x
P4.x
OUTPUT DATA
n
INPUT DATA
READ PIN
NOTE:
1. Port 2 p1 assists the logic-one output for memory bus cycles.
Figure 4. Internal Pull-Up Configurations
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T89C51AC2
5. SFR Mapping
The Special Function Registers (SFRs) of the T89C51AC2 fall into the following categories:
Table 3. C51 Core SFRs
Mnemonic Add
Name
7
ACC
E0h Accumulator
B
F0h
PSW
D0h Program Status Word
SP
81h
Stack Pointer
LSB of SPX
DPL
82h
Data Pointer Low byte
LSB of DPTR
DPH
83h
Data Pointer High byte
MSB of DPTR
6
5
4
3
2
1
0
4
3
2
1
0
B Register
Table 4. I/O Port SFRs
Mnemonic Add
Name
P0
80h
Port 0
P1
90h
Port 1
P2
A0h Port 2
P3
B0h Port 3
P4
C0h Port 4 (x2)
7
6
5
Table 5. Timers SFRs
Mnemonic Add
Name
TH0
8Ch Timer/Counter 0 High byte
TL0
8Ah Timer/Counter 0 Low byte
TH1
8Dh Timer/Counter 1 High byte
7
6
5
4
3
2
1
0
TF0
TR0
IE1
IT1
IE0
IT0
TL1
8Bh Timer/Counter 1 Low byte
TH2
CDh Timer/Counter 2 High byte
TL2
CCh Timer/Counter 2 Low byte
TCON
88h
Timer/Counter 0 and 1 control
TF1
TR1
TMOD
89h
Timer/Counter 0 and 1 Modes
GATE1
C/T1#
M11
M01
GATE0
C/T0#
M10
M00
T2CON
C8h Timer/Counter 2 control
TF2
EXF2
RCLK
TCLK
EXEN2
TR2
C/T2#
CP/RL2#
T2MOD
C9h Timer/Counter 2 Mode
-
-
-
-
-
-
T2OE
DCEN
RCAP2H
Timer/Counter 2 Reload/Capture
CBh
High byte
RCAP2L
CAh
WDTRST
A6h WatchDog Timer Reset
WDTPRG
A7h WatchDog Timer Program
-
-
-
-
-
S2
S1
S0
Timer/Counter 2 Reload/Capture
Low byte
Table 6. Serial I/O Port SFRs
Mnemonic Add
Name
SCON
98h
Serial Control
SBUF
99h
Serial Data Buffer
SADEN
B9h Slave Address Mask
7
6
5
4
3
2
1
0
FE/SM0
SM1
SM2
REN
TB8
RB8
TI
RI
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Mnemonic Add
SADDR
Name
7
6
5
4
3
2
1
0
5
4
3
2
1
0
A9h Slave Address
Table 7. PCA SFRs
Mnemonic Add
Name
7
CCON
D8h PCA Timer/Counter Control
CMOD
D9h PCA Timer/Counter Mode
CL
E9h PCA Timer/Counter Low byte
CH
F9h
PCA Timer/Counter High byte
CCAPM0
CCAPM1
CCAPM2
CCAPM3
CCAPM4
DAh
DBh
DCh
DDh
DEh
PCA
PCA
PCA
PCA
PCA
CCAP0H
CCAP1H
CCAP2H
CCAP3H
CCAP4H
FAh
FBh
FCh
FDh
FEh
CCAP0L
CCAP1L
CCAP2L
CCAP3L
CCAP4L
EAh
EBh
ECh
EDh
EEh
6
CF
CR
-
CCF4
CCF3
CCF2
CCF1
CCF0
CIDL
WDTE
-
-
-
CPS1
CPS0
ECF
-
ECOM0
ECOM1
ECOM2
ECOM3
ECOM4
CAPP0
CAPP1
CAPP2
CAPP3
CAPP4
CAP0
CAP1
CAP2
CAP3
CAP4
MAT0
MAT1
MAT2
MAT3
MAT4
TOG0
TOG1
TOG2
TOG3
TOG4
PWM0
PWM1
PWM2
PWM3
PWM4
ECCF0
ECCF1
ECCF2
ECCF3
ECCF4
PCA Compare Capture Module 0 H
PCA Compare Capture Module 1 H
PCA Compare Capture Module 2 H
PCA Compare Capture Module 3 H
PCA Compare Capture Module 4 H
CCAP0H7
CCAP1H7
CCAP2H7
CCAP3H7
CCAP4H7
CCAP0H6
CCAP1H6
CCAP2H6
CCAP3H6
CCAP4H6
CCAP0H5
CCAP1H5
CCAP2H5
CCAP3H5
CCAP4H5
CCAP0H4
CCAP1H4
CCAP2H4
CCAP3H4
CCAP4H4
CCAP0H3
CCAP1H3
CCAP2H3
CCAP3H3
CCAP4H3
CCAP0H2
CCAP1H2
CCAP2H2
CCAP3H2
CCAP4H2
CCAP0H1
CCAP1H1
CCAP2H1
CCAP3H1
CCAP4H1
CCAP0H0
CCAP1H0
CCAP2H0
CCAP3H0
CCAP4H0
PCA Compare Capture Module 0 L
PCA Compare Capture Module 1 L
PCA Compare Capture Module 2 L
PCA Compare Capture Module 3 L
PCA Compare Capture Module 4 L
CCAP0L7
CCAP1L7
CCAP2L7
CCAP3L7
CCAP4L7
CCAP0L6
CCAP1L6
CCAP2L6
CCAP3L6
CCAP4L6
CCAP0L5
CCAP1L5
CCAP2L5
CCAP3L5
CCAP4L5
CCAP0L4
CCAP1L4
CCAP2L4
CCAP3L4
CCAP4L4
CCAP0L3
CCAP1L3
CCAP2L3
CCAP3L3
CCAP4L3
CCAP0L2
CCAP1L2
CCAP2L2
CCAP3L2
CCAP4L2
CCAP0L1
CCAP1L1
CCAP2L1
CCAP3L1
CCAP4L1
CCAP0L0
CCAP1L0
CCAP2L0
CCAP3L0
CCAP4L0
1
0
Timer/Counter
Timer/Counter
Timer/Counter
Timer/Counter
Timer/Counter
Mode
Mode
Mode
Mode
Mode
0
1
2
3
4
Table 8. Interrupt SFRs
Mnemonic Add
Name
7
6
5
4
3
2
IEN0
A8h Interrupt Enable Control 0
EA
AC
ET2
ES
ET1
EX1
ET0
EX0
IEN1
E8h Interrupt Enable Control 1
-
-
-
-
-
-
EADC
-
IPL0
B8h Interrupt Priority Control Low 0
-
PPC
PT2
PS
PT1
PX1
PT0
PX0
IPH0
B7h Interrupt Priority Control High 0
-
PPCH
PT2H
PSH
PT1H
PX1H
PT0H
PX0H
IPL1
F8h
Interrupt Priority Control Low 1
-
-
-
-
-
-
PADCL
-
IPH1
F7h
Interrupt Priority Control High1
-
-
-
-
-
-
PADCH
-
Table 9. ADC SFRs
Mnemonic Add
Name
ADCON
F3h
ADC Control
ADCF
F6h
ADC Configuration
7
6
5
4
3
2
1
0
-
PSIDLE
ADEN
ADEOC
ADSST
SCH2
SCH1
SCH0
CH7
CH6
CH5
CH4
CH3
CH2
CH1
CH0
ADCLK
F2h
ADC Clock
-
-
-
PRS4
PRS3
PRS2
PRS1
PRS0
ADDH
F5h
ADC Data High byte
ADAT9
ADAT8
ADAT7
ADAT6
ADAT5
ADAT4
ADAT3
ADAT2
ADDL
F4h
ADC Data Low byte
-
-
-
-
-
-
ADAT1
ADAT0
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Table 10. Other SFRs
Mnemonic Add
PCON
Name
87hh Power Control
7
6
5
4
3
2
1
0
SMOD1
SMOD0
-
POF
GF1
GF0
PD
IDL
AUXR
8Eh Auxiliary Register 0
-
M(1)
M0
-
XRS1
XRS2
EXTRAM
A0
AUXR1
A2h Auxiliary Register 1
-
-
ENBOOT
-
GF3
-
-
DPS
CKCON
8Fh
FCON
D1h FLASH Control
Clock Control
EECON
D2h EEPROM Contol
-
WDX2
PCAX2
SIX2
T2X2
T1X2
T0X2
X2
FPL3
FPL2
FPL1
FPL0
FPS
FMOD1
FMOD0
FBUSY
EEPL3
EEPL2
EEPL1
EEPL0
-
-
EEE
EEBUSY
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Table 11. SFR’s mapping
0/8(1)
1/9
2/A
3/B
4/C
5/D
6/E
F8h
IPL1
xxxx x000
CH
0000 0000
CCAP0H
0000 0000
CCAP1H
0000 0000
CCAP2H
0000 0000
CCAP3H
0000 0000
CCAP4H
0000 0000
F0h
B
0000 0000
ADCLK
xx00 0000
ADCON
x000 0000
ADDL
0000 0000
ADDH
0000 0000
ADCF
0000 0000
E8h
IEN1
xxxx x000
CCAP0L
0000 0000
CCAP1L
0000 0000
CCAP2L
0000 0000
CCAP3L
0000 0000
CCAP4L
0000 0000
E0h
ACC
0000 0000
D8h
CCON
00xx xx00
CMOD
00xx x000
CCAPM0
x000 0000
D0h
PSW
0000 0000
FCON
0000 0000
EECON
xxxx xx00
C8h
T2CON
0000 0000
T2MOD
xxxx xx00
RCAP2L
0000 0000
C0h
P4
xxxx xx11
B8h
IPL0
x000 0000
B0h
P3
1111 1111
A8h
IEN0
0000 0000
A0h
P2
1111 1111
98h
SCON
0000 0000
90h
P1
1111 1111
88h
TCON
0000 0000
TMOD
0000 0000
TL0
0000 0000
TL1
0000 0000
80h
P0
1111 1111
SP
0000 0111
DPL
0000 0000
DPH
0000 0000
0/8(1)
1/9
2/A
3/B
CL
0000 0000
7/F
FFh
IPH1
xxxx x000
F7h
EFh
E7h
CCAPM1
x000 0000
CCAPM2
x000 0000
CCAPM3
x000 0000
CCAPM4
x000 0000
DFh
D7h
RCAP2H
0000 0000
TL2
0000 0000
TH2
0000 0000
CANEN1
xx00 0000
CANEN2
0000 0000
CFh
C7h
SADEN
0000 0000
BFh
IPH0
x000 0000
SADDR
0000 0000
B7h
AFh
AUXR1
0000 0000
WDTRST
1111 1111
WDTPRG
xxxx x000
SBUF
0000 0000
A7h
9Fh
97h
TH0
0000 0000
4/C
TH1
0000 0000
5/D
AUXR
0000 1000
6/E
CKCON
0000 0000
8Fh
PCON
0000 0000
87h
7/F
Note:
2. These registers are bit-addressable.
Sixteen addresses in the SFR space are both byte-addressable and bit-addressable. The bit-addressable SFR’s are those whose address
ends in 0 and 8. The bit addresses, in this area, are 0x80 through to 0xFF.
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6. Clock
6.1. Introduction
The T89C51AC2 core needs only 6 clock periods per machine cycle. This feature, called ”X2”, provides the
following advantages:
•
•
•
•
Divides frequency crystals by 2 (cheaper crystals) while keeping the same CPU power.
Saves power consumption while keeping the same CPU power (oscillator power saving).
Saves power consumption by dividing dynamic operating frequency by 2 in operating and idle modes.
Increases CPU power by 2 while keeping the same crystal frequency.
In order to keep the original C51 compatibility, a divider-by-2 is inserted between the XTAL1 signal and the main
clock input of the core (phase generator). This divider may be disabled by the software.
An extra feature is available for selected hardware in the X2 mode. This feature allows starting of the CPU in the
X2 mode, without starting in the standard mode.
The hardware CPU X2 mode can be read and write via IAP (SetX2mode, ClearX2mode, ReadX2mode), see InSystem Programming section.
These IAPs are detailed in the "In-System Programming" section.
6.2. Description
The clock for the whole circuit and peripheral is first divided by two before being used by the CPU core and
peripherals. This allows any cyclic ratio to be accepted on the XTAL1 input. In X2 mode, as this divider is
bypassed, the signals on XTAL1 must have a cyclic ratio between 40 to 60%. Figure 5. shows the clock generation
block diagram. The X2 bit is validated on the XTAL1÷2 rising edge to avoid glitches when switching from the
X2 to the STD mode. Figure 6 shows the mode switching waveforms.
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PCON.0
X2
IDL
CKCON.0
X2B
Hardware byte
÷2
XTAL1
CPU Core
Clock
0
1
XTAL2
CPU
CLOCK
PD
CPU Core Clock Symbol
PCON.1
÷2
1
FT0 Clock
0
÷2
1
FT1 Clock
0
÷2
1
FT2 Clock
0
÷2
1
FUart Clock
0
÷2
1
FPca Clock
0
÷2
1
FWd Clock
0
PERIPH
CLOCK
X2
CKCON.0
Peripheral Clock Symbol
WDX2
PCAX2
SIX2
T2X2
T1X2
T0X2
CKCON.6
CKCON.5
CKCON.4
CKCON.3
CKCON.2
CKCON.1
Figure 5. Clock CPU Generation Diagram
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XTAL1
XTAL2
X2 bit
CPU clock
STD Mode
X2 Mode
STD Mode
Figure 6. Mode Switching Waveforms
The X2 bit in the CKCON register (See Table 7) allows switching from 12 clock cycles per instruction to 6 clock
cycles and vice versa. At reset, the standard speed is activated (STD mode). Setting this bit activates the X2 feature
(X2 mode).
CAUTION
In order to prevent any incorrect operation while operating in the X2 mode, users must be aware that all peripherals
using the clock frequency as a time reference (UART, timers...) will have their time reference divided by two. For
example a free running timer generating an interrupt every 20 ms will then generate an interrupt every 10 ms. A
UART with a 4800 baud rate will have a 9600 baud rate.
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6.3. Register
CKCON (S:8Fh)
Clock Control Register
7
6
5
4
3
2
1
0
-
WDX2
PCAX2
SIX2
T2X2
T1X2
T0X2
X2
Bit Number Bit Mnemonic
Description
Reserved
The value read from this bit is indeterminate. Do not set this bit.
7
-
6
WDX2
Watchdog clock (1)
Clear to select 6 clock periods per peripheral clock cycle.
Set to select 12 clock periods per peripheral clock cycle.
5
PCAX2
Programmable Counter Array clock (1)
Clear to select 6 clock periods per peripheral clock cycle.
Set to select 12 clock periods per peripheral clock cycle.
4
SIX2
Enhanced UART clock (MODE 0 and 2) (1)
Clear to select 6 clock periods per peripheral clock cycle.
Set to select 12 clock periods per peripheral clock cycle.
3
T2X2
Timer2 clock (1)
Clear to select 6 clock periods per peripheral clock cycle.
Set to select 12 clock periods per peripheral clock cycle.
2
T1X2
Timer1 clock (1)
Clear to select 6 clock periods per peripheral clock cycle.
Set to select 12 clock periods per peripheral clock cycle.
1
T0X2
Timer0 clock (1)
Clear to select 6 clock periods per peripheral clock cycle.
Set to select 12 clock periods per peripheral clock cycle.
0
X2
CPU clock
Clear to select 12 clock periods per machine cycle (STD mode) for CPU and all the peripherals.
Set to select 6 clock periods per machine cycle (X2 mode) and to enable the individual peripherals "X2"bits.
NOTE:
1. This control bit is validated when the CPU clock bit X2 is set; when X2 is low, this bit has no effect.
Reset Value = 0000 0000b
Figure 7. CKCON Register
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7. Program/Code Memory
7.1. Introduction
The T89C51AC2 implement 32 Kbytes of on-chip program/code memory. Figure 8 shows the split of internal and
external program/code memory spaces depending on the product.
The FLASH memory increases EPROM and ROM functionality by in-circuit electrical erasure and programming.
Thanks to the internal charge pump, the high voltage needed for programming or erasing FLASH cells is generated
on-chip using the standard VDD voltage. Thus, the FLASH Memory can be programmed using only one voltage
and allows in application software programming commonly known as IAP. Hardware programming mode is also
available using specific programming tool.
FFFFh
32 Kbytes
External Code
8000h
7FFFh1
32 Kbytes
FLASH
0000h
T89C51AC2
Figure 8. Program/Code Memory Organization
Caution:
1. If the program executes exclusively from on-chip code memory (not from external memory), beware of executing code from the upper byte
of on-chip memory (7FFFh) and thereby disrupt I/O Ports 0 and 2 due to external prefetch. Fetching code constant from this location
does not affect Ports 0 and 2.
7.2. External Code Memory Access
7.2.1. Memory Interface
The external memory interface comprises the external bus (port 0 and port 2) as well as the bus control signals
(PSEN#, and ALE).
Figure 9 shows the structure of the external address bus. P0 carries address A7:0 while P2 carries address A15:8.
Data D7:0 is multiplexed with A7:0 on P0. Table 12 describes the external memory interface signals.
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T89C51AC2
FLASH
EPROM
T89C51AC2
A15:8
P2
A15:8
ALE
AD7:0
Latch
P0
A7:0
A7:0
D7:0
PSEN#
OE
Figure 9. External Code Memory Interface Structure
Table 12. External Data Memory Interface Signals
Signal
Name
Type
Alternate
Function
A15:8
O
AD7:0
I/O
ALE
O
Address Latch Enable
ALE signals indicates that valid address information are available on lines AD7:0.
-
PSEN#
O
Program Store Enable Output
This signal is active low during external code fetch or external code read (MOVC instruction).
-
Description
Address Lines
Upper address lines for the external bus.
P2.7:0
Address/Data Lines
Multiplexed lower address lines and data for the external memory.
P0.7:0
7.2.2. External Bus Cycles
This section describes the bus cycles the T89C51AC2 executes to fetch code (see Figure 10) in the external program/
code memory.
External memory cycle takes 6 CPU clock periods. This is equivalent to 12 oscillator clock period in standard
mode or 6 oscillator clock periods in X2 mode. For further information on X2 mode.(see the clock Section)
For simplicity, the accompanying figure depicts the bus cycle waveforms in idealized form and do not provide
precise timing information.
CPU Clock
ALE
PSEN#
P0 D7:0
P2 PCH
PCL
D7:0
PCL
PCH
D7:0
PCH
Figure 10. External Code Fetch Waveforms
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7.3. FLASH Memory Architecture
T89C51AC2 features two on-chip flash memories:
• Flash memory FM0:
containing 32 Kbytes of program memory (user space) organized into 128 byte pages,
• Flash memory FM1:
2 Kbytes for boot loader and Application Programming Interfaces (API).
The FM0 supports both parallel programming and Serial In-System Programming (ISP) whereas FM1 supports
only parallel programming by programmers. The ISP mode is detailed in the "In-System Programming" section.
All Read/Write access operations on FLASH Memory by user application are managed by a set of API described
in the "In-System Programming" section.
2 Kbytes
Flash memory
boot space
Hardware Security (1 byte)
Extra Row (128 bytes)
Column Latches (128 bytes)
FM1
7FFFh
32 Kbytes
FFFFh
F800h
FM1 mapped between FFFFh and
F800h when bit ENBOOT is set in
AUXR1 register
Flash memory
user space
FM0
0000h
Figure 11. Flash memory architecture
7.3.1. FM0 Memory Architecture
The flash memory is made up of 4 blocks (see Figure 11):
1. The memory array (user space) 32 Kbytes
2. The Extra Row
3. The Hardware security bits
4. The column latch registers
7.3.1.1. User Space
This space is composed of a 32 Kbytes FLASH memory organized in 256 pages of 128 bytes. It contains the
user’s application code.
7.3.1.2. Extra Row (XRow)
This row is a part of FM0 and has a size of 128 bytes. The extra row may contain information for boot loader usage.
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7.3.1.3. Hardware security space
The Hardware security space is a part of FM0 and has a size of 1 byte.
The 4 MSB can be read/written by software, the 4 LSB can only be read by software and written by hardware in
parallel mode.
7.3.1.4. Column latches
The column latches, also part of FM0, have a size of full page (128 bytes).
The column latches are the entrance buffers of the three previous memory locations (user array, XROW and
Hardware security byte).
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7.4. Overview of FM0 operations
The CPU interfaces to the flash memory through the FCON register and AUXR1 register.
These registers are used to:
•
•
•
•
Map the memory spaces in the adressable space
Launch the programming of the memory spaces
Get the status of the flash memory (busy/not busy)
Select the flash memory FM0/FM1.
7.4.1. Mapping of the memory space
By default, the user space is accessed by MOVC instruction for read only. The column latches space is made
accessible by setting the FPS bit in FCON register. Writing is possible from 0000h to 7FFFh, address bits 6 to 0
are used to select an address within a page while bits 14 to 7 are used to select the programming address of the page.
Setting this bit takes precedence on the EXTRAM bit in AUXR register.
The other memory spaces (user, extra row, hardware security) are made accessible in the code segment by
programming bits FMOD0 and FMOD1 in FCON register in accordance with Table 13. A MOVC instruction is
then used for reading these spaces.
Table 13. .FM0 blocks select bits
FMOD1
FMOD0
FM0 Adressable space
0
0
User (0000h-FFFFh)
0
1
Extra Row(FF80h-FFFFh)
1
0
Hardware Security (0000h)
1
1
reserved
7.4.2. Launching programming
FPL3:0 bits in FCON register are used to secure the launch of programming. A specific sequence must be written
in these bits to unlock the write protection and to launch the programming. This sequence is 5 followed by A.
Table 14 summarizes the memory spaces to program according to FMOD1:0 bits.
Table 14. Programming spaces
Write to FCON
Operation
User
Extra Row
Security Space
Reserved
FPL3:0
FPS
FMOD1
FMOD0
5
X
0
0
No action
A
X
0
0
Write the column latches in user space
5
X
0
1
No action
A
X
0
1
Write the column latches in extra row space
5
X
1
0
No action
A
X
1
0
Write the fuse bits space
5
X
1
1
No action
A
X
1
1
No action
The FLASH memory enters a busy state as soon as programming is launched. In this state, the memory is no
more available for fetching code.
Caution:
Interrupts that may occur during programming time must be disable to avoid any spurious exit of the idle mode.
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7.4.3. Status of the flash memory
The bit FBUSY in FCON register is used to indicate the status of programming.
FBUSY is set when programming is in progress.
7.4.4. Selecting FM0/FM1
The bit ENBOOT in AUXR1 register is used to choose between FM0 and FM1 mapped up to F800h.
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7.4.5. Loading the Column Latches
Any number of data from 1 byte to 128 bytes can be loaded in the column latches. This provides the capability
to program the whole memory by byte, by page or by any number of bytes in a page.
When programming is launched, an automatic erase of the locations loaded in the column latches is first performed,
then programming is effectively done. Thus no page or block erase is needed and only the loaded data are
programmed in the corresponding page.
The following procedure is used to load the column latches and is summarized in Figure 12:
•
•
•
•
•
Map the column latch space by setting FPS bit.
Load the DPTR with the address to load.
Load Accumulator register with the data to load.
Execute the MOVX @DPTR, A instruction.
If needed loop the three last instructions until the page is completely loaded.
Column Latches
Loading
Column Latches Mapping
FPS= 1
Data Load
DPTR= Address
ACC= Data
Exec: MOVX @DPTR, A
Last Byte
to load?
Data memory Mapping
FPS= 0
Figure 12. Column Latches Loading Procedure
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7.4.6. Programming the FLASH Spaces
User
The following procedure is used to program the User space and is summarized in Figure 13:
• Load data in the column latches from address 0000h to 7FFFh1.
• Disable the interrupts.
• Launch the programming by writing the data sequence 50h followed by A0h in FCON register.
The end of the programming indicated by the FBUSY flag cleared.
• Enable the interrupts.
Note:
1. The last page address used when loading the column latch is the one used to select the page programming address.
Extra Row
The following procedure is used to program the Extra Row space and is summarized in Figure 13:
• Load data in the column latches from address FF80h to FFFFh.
• Disable the interrupts.
• Launch the programming by writing the data sequence 52h followed by A2h in FCON register.
The end of the programming indicated by the FBUSY flag cleared.
• Enable the interrupts.
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FLASH Spaces
Programming
Column Latches Loading
see Figure 12
Disable IT
EA= 0
Launch Programming
FCON= 5xh
FCON= Axh
FBusy
Cleared?
Erase Mode
FCON = 00h
End Programming
Enable IT
EA= 1
Figure 13. Flash and Extra row Programming Procedure
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Hardware Security
The following procedure is used to program the Hardware Security space and is summarized in Figure 14:
•
•
•
•
•
•
Set FPS and map Harware byte (FCON = 0x0C)
Disable the interrupts.
Load DPTR at address 0000h.
Load Accumulator register with the data to load.
Execute the MOVX @DPTR, A instruction.
Launch the programming by writing the data sequence 54h followed by A4h in FCON register.
The end of the programming indicated by the FBusy flag cleared.
• Enable the interrupts.
FLASH Spaces
Programming
FCON = 0Ch
Data Load
DPTR= 00h
ACC= Data
Exec: MOVX @DPTR, A
Disable IT
EA= 0
Launch Programming
FCON= 54h
FCON= A4h
FBusy
Cleared?
Erase Mode
FCON = 00h
End Programming
Enable IT
EA= 1
Figure 14. Hardware Programming Procedure
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7.4.7. Reading the FLASH Spaces
User
The following procedure is used to read the User space and is summarized in Figure 15:
• Map the User space by writing 00h in FCON register.
• Read one byte in Accumulator by executing MOVC A,@A+DPTR with A= 0 & DPTR= 0000h to FFFFh.
Extra Row
The following procedure is used to read the Extra Row space and is summarized in Figure 15:
• Map the Extra Row space by writing 02h in FCON register.
• Read one byte in Accumulator by executing MOVC A,@A+DPTR with A= 0 & DPTR= FF80h to FFFFh.
Hardware Security
The following procedure is used to read the Hardware Security space and is summarized in Figure 15:
• Map the Hardware Security space by writing 04h in FCON register.
• Read the byte in Accumulator by executing MOVC A,@A+DPTR with A= 0 & DPTR= 0000h.
FLASH Spaces
Reading
FLASH Spaces Mapping
FCON= 00000xx0b
Data Read
DPTR= Address
ACC= 0
Exec: MOVC A, @A+DPTR
Erase Mode
FCON = 00h
Figure 15. Reading Procedure
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7.5. Registers
FCON (S:D1h)
FLASH Control Register
7
6
5
4
3
2
1
0
FPL3
FPL2
FPL1
FPL0
FPS
FMOD1
FMOD0
FBUSY
Bit Number Bit Mnemonic
7-4
FPL3:0
3
FPS
2-1
FMOD1:0
0
FBUSY
Description
Programming Launch Command Bits
Write 5Xh followed by AXh to launch the programming according to FMOD1:0. (see Table 14.)
FLASH Map Program Space
Set to map the column latch space in the data memory space.
Clear to re-map the data memory space.
FLASH Mode
See Table 13 or Table 14.
FLASH Busy
Set by hardware when programming is in progress.
Clear by hardware when programming is done.
Can not be cleared by software.
Reset Value= 0000 0000b
Figure 16. FCON Register
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8. Data Memory
8.1. Introduction
The T89C51AC2 provides data memory access in two different spaces:
1. The internal space mapped in three separate segments:
• the lower 128 bytes RAM segment.
• the upper 128 bytes RAM segment.
• the expanded 1024 bytes RAM segment (ERAM).
2. The external space.
A fourth internal segment is available but dedicated to Special Function Registers, SFRs, (addresses 80h to FFh)
accessible by direct addressing mode.
Figure 17 shows the internal and external data memory spaces organization.
FFFFh
64 Kbytes
External XRAM
FFh
FFh or 3FFh
256 up to 1024 bytes
Internal ERAM
EXTRAM= 0
00h
FFh
Upper
128 bytes
Internal RAM
indirect addressing
80h
7Fh
00h
Special
Function
Registers
direct addressing
80h
Lower
128 bytes
Internal RAM
direct or indirect
addressing
0100h up to 0400h
0000h
EXTRAM= 1
Figure 17. Internal and External Data Memory Organization
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8.2. Internal Space
8.2.1. Lower 128 Bytes RAM
The lower 128 bytes of RAM (see Figure 17) are accessible from address 00h to 7Fh using direct or indirect
addressing modes. The lowest 32 bytes are grouped into 4 banks of 8 registers (R0 to R7). Two bits RS0 and RS1
in PSW register (see Figure 23) select which bank is in use according to Table 15. This allows more efficient use
of code space, since register instructions are shorter than instructions that use direct addressing, and can be used
for context switching in interrupt service routines.
Table 15. Register Bank Selection
RS1
RS0
Description
0
0
Register bank 0 from 00h to 07h
0
1
Register bank 0 from 08h to 0Fh
1
0
Register bank 0 from 10h to 17h
1
1
Register bank 0 from 18h to 1Fh
The next 16 bytes above the register banks form a block of bit-addressable memory space. The C51 instruction
set includes a wide selection of single-bit instructions, and the 128 bits in this area can be directly addressed by
these instructions. The bit addresses in this area are 00h to 7Fh.
7Fh
30h
2Fh
20h
18h
10h
08h
00h
Bit-Addressable Space
(Bit Addresses 0-7Fh)
1Fh
17h
0Fh
4 Banks of
8 Registers
R0-R7
07h
Figure 18. Lower 128 bytes Internal RAM Organization
8.2.2. Upper 128 Bytes RAM
The upper 128 bytes of RAM are accessible from address 80h to FFh using only indirect addressing mode.
8.2.3. Expanded RAM
The on-chip 1024 bytes of expanded RAM (ERAM) are accessible from address 0000h to 03FFh using indirect
addressing mode through MOVX instructions. In this address range, the bit EXTRAM in AUXR register is used
to select the ERAM (default) or the XRAM. As shown in Figure 17 when EXTRAM= 0, the ERAM is selected
and when EXTRAM= 1, the XRAM is selected.
Caution:
Lower 128 bytes RAM, Upper 128 bytes RAM, and expanded RAM are made of volatile memory cells. This means that the RAM content is
indeterminate after power-up and must then be initialized properly.
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8.3. External Space
8.3.1. Memory Interface
The external memory interface comprises the external bus (port 0 and port 2) as well as the bus control signals
(RD#, WR#, and ALE).
Figure 19 shows the structure of the external address bus. P0 carries address A7:0 while P2 carries address A15:8.
Data D7:0 is multiplexed with A7:0 on P0. Table 16 describes the external memory interface signals.
RAM
PERIPHERAL
<Generic
A15:8
P2
A15:8
ALE
AD7:0
P0
Latch
A7:0
A7:0
D7:0
RD#
WR#
OE
WR
Figure 19. External Data Memory Interface Structure
Table 16. External Data Memory Interface Signals
Signal Name
Type
Description
Alternative Function
A15:8
O
AD7:0
I/O
ALE
O
Address Latch Enable
ALE signals indicates that valid address information are available on lines AD7:0.
RD#
O
Read
Read signal output to external data memory.
P3.7
WR#
O
Write
Write signal output to external memory.
P3.6
Address Lines
Upper address lines for the external bus.
P2.7:0
Address/Data Lines
Multiplexed lower address lines and data for the external memory.
P0.7:0
-
8.3.2. External Bus Cycles
This section describes the bus cycles the T89C51AC2 executes to read (see Figure 20), and write data (see Figure 21)
in the external data memory.
External memory cycle takes 6 CPU clock periods. This is equivalent to 12 oscillator clock period in standard
mode or 6 oscillator clock periods in X2 mode. For further information on X2 mode.
Slow peripherals can be accessed by stretching the read and write cycles. This is done using the M0 bit in AUXR
register. Setting this bit changes the width of the RD# and WR# signals from 3 to 15 CPU clock periods.
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For simplicity, the accompanying figures depict the bus cycle waveforms in idealized form and do not provide
precise timing information. For bus cycle timing parameters refer to the Section “AC Characteristics” of the
T89C51AC2 datasheet.
CPU Clock
ALE
RD#1
P0
P2
DPL or Ri
D7:0
DPH or P22,3
P2
Figure 20. External Data Read Waveforms
Notes:
1. RD# signal may be stretched using M0 bit in AUXR register.
2. When executing MOVX @Ri instruction, P2 outputs SFR content.
3. When executing MOVX @DPTR instruction, if DPHDIS is set (Page Access Mode), P2 outputs SFR content instead of DPH.
CPU Clock
ALE
WR#1
P0
P2
DPL or Ri
P2
D7:0
DPH or P22,3
Figure 21. External Data Write Waveforms
Notes:
1. WR# signal may be stretched using M0 bit in AUXR register.
2. When executing MOVX @Ri instruction, P2 outputs SFR content.
3. When executing MOVX @DPTR instruction, if DPHDIS is set (Page Access Mode), P2 outputs SFR content instead of DPH.
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8.4. Dual Data Pointer
8.4.1. Description
The T89C51AC2 implements a second data pointer for speeding up code execution and reducing code size in case
of intensive usage of external memory accesses.
DPTR0 and DPTR1 are seen by the CPU as DPTR and are accessed using the SFR addresses 83h and 84h that
are the DPH and DPL addresses. The DPS bit in AUXR1 register (see Figure 25) is used to select whether DPTR
is the data pointer 0 or the data pointer 1 (see Figure 22).
DPL0
0
DPL1
1
DPL
DPTR0
DPS
DPTR1
DPH0
0
DPH1
1
AUXR1.0
DPTR
DPH
Figure 22. Dual Data Pointer Implementation
8.4.2. Application
Software can take advantage of the additional data pointers to both increase speed and reduce code size, for
example, block operations (copy, compare, search …) are well served by using one data pointer as a “source”
pointer and the other one as a “destination” pointer.
Hereafter is an example of block move implementation using the two pointers and coded in assembler. Latest C
compiler take also advantage of this feature by providing enhanced algorithm libraries.
The INC instruction is a short (2 bytes) and fast (6 CPU clocks) way to manipulate the DPS bit in the AUXR1
register. However, note that the INC instruction does not directly force the DPS bit to a particular state, but simply
toggles it. In simple routines, such as the block move example, only the fact that DPS is toggled in the proper
sequence matters, not its actual value. In other words, the block move routine works the same whether DPS is '0'
or '1' on entry.
;
;
;
;
ASCII block move using dual data pointers
Modifies DPTR0, DPTR1, A and PSW
Ends when encountering NULL character
Note: DPS exits opposite of entry state unless an extra INC AUXR1 is added
AUXR1
EQU
0A2h
move:
mov
inc
mov
inc
movx
inc
inc
movx
inc
jnz
DPTR,#SOURCE
AUXR1
DPTR,#DEST
AUXR1
A,@DPTR
DPTR
AUXR1
@DPTR,A
DPTR
mv_loop
mv_loop:
;
;
;
;
;
;
;
;
;
;
address of SOURCE
switch data pointers
address of DEST
switch data pointers
get a byte from SOURCE
increment SOURCE address
switch data pointers
write the byte to DEST
increment DEST address
check for NULL terminator
end_move:
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8.5. Registers
PSW (S:8Eh)
Program Status Word Register.
7
6
5
4
3
2
1
0
CY
AC
F0
RS1
RS0
OV
F1
P
Bit Number Bit Mnemonic
Description
7
CY
Carry Flag
Carry out from bit 1 of ALU operands.
6
AC
Auxiliary Carry Flag
Carry out from bit 1 of addition operands.
5
F0
User Definable Flag 0.
4-3
RS1:0
Register Bank Select Bits
Refer to Table 15 for bits description.
2
OV
Overflow Flag
Overflow set by arithmetic operations.
1
F1
User Definable Flag 1.
0
P
Parity Bit
Set when ACC contains an odd number of 1’s.
Cleared when ACC contains an even number of 1’s.
Reset Value= 0000 0000b
Figure 23. PSW Register
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AUXR (S:8Eh)
Auxiliary Register
7
6
5
4
3
2
1
0
-
-
M0
-
XRS1
XRS0
EXTRAM
A0
Bit Number
Bit Mnemonic
7-6
-
5
M0
4
-
3-2
XRS1-0
1
EXTRAM
0
A0
Description
Reserved
The value read from these bits are indeterminate. Do not set this bit.
Stretch MOVX control:
the RD/ and the WR/ pulse length is increased according to the value of M0.
M0
Pulse length in clock period
0
6
1
30
Reserved
The value read from this bit is indeterminate. Do not set this bit.
ERAM size:
Accessible size of the ERAM
XRS1:0 ERAM size
0 0
256 bytes
0 1
512 bytes
1 0
768 bytes
1 1
1024 bytes (default)
Internal/External RAM (00h - FFh)
access using MOVX @ Ri /@ DPTR
0 - Internal ERAM access using MOVX @ Ri / @ DPTR.
1 - External data memory access.
Disable/Enable ALE)
0 - ALE is emitted at a constant rate of 1/6 the oscillator frequency (or 1/3 if X2 mode is used)
1 - ALE is active only during a MOVX or MOVC instruction.
Reset Value= X00X 1100b
Not bit addressable
Figure 24. AUXR Register
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AUXR1 (S:A2h)
Auxiliary Control Register 1.
7
6
5
4
3
2
1
0
-
-
ENBOOT
-
GF3
0
-
DPS
Bit Number Bit Mnemonic
Description
Reserved
The value read from these bits is indeterminate. Do not set these bits.
7-6
-
5
ENBOOT
4
-
3
GF3
2
0
Always Zero
This bit is stuck to logic 0 to allow INC AUXR1 instruction without affecting GF3 flag.
1
-
Reserved for Data Pointer Extension.
0
DPS
Enable Boot Flash
Set this bit for map the boot flash between F800h -FFFFh
Clear this bit for disable boot flash.
Reserved
The value read from this bit is indeterminate. Do not set this bit.
General Purpose Flag 3.
Data Pointer Select Bit
Set to select second dual data pointer: DPTR1.
Clear to select first dual data pointer: DPTR0.
Reset Value= XXXX 00X0b
Figure 25. AUXR1 Register
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9. EEPROM data memory
9.1. General description
The 2k byte on-chip EEPROM memory block is located at addresses 0000h to 07FFh of the XRAM memory space
and is selected by setting control bits in the EECON register.
A read in the EEPROM memory is done with a MOVX instruction.
A physical write in the EEPROM memory is done in two steps: write data in the column latches and transfer of
all data latches into an EEPROM memory row (programming).
The number of data written on the page may vary from 1 to 128 bytes (the page size). When programming, only
the data written in the column latch is programmed and a ninth bit is used to obtain this feature. This provides
the capability to program the whole memory by bytes, by page or by a number of bytes in a page. Indeed, each
ninth bit is set when the writing the corresponding byte in a row and all these ninth bits are reset after the writing
of the complete EEPROM row.
9.2. Write Data in the column latches
Data is written by byte to the column latches as for an external RAM memory. Out of the 11 address bits of the
data pointer, the 4 MSBs are used for page selection (row) and 7 are used for byte selection. Between two EEPROM
programming sessions, all the addresses in the column latches must stay on the same page, meaning that the 4
MSB must no be changed.
The following procedure is used to write to the column latches:
•
•
•
•
•
Set bit EEE of EECON register
Load DPTR with the address to write
Store A register with the data to be written
Execute a MOVX @DPTR, A
If needed loop the three last instructions until the end of a 128 bytes page
9.3. Programming
The EEPROM programming consists on the following actions:
• writing one or more bytes of one page in the column latches. Normally, all bytes must belong to the same
page; if not, the first page address will be latched and the others discarded.
• launching programming by writing the control sequence (54h followed by A4h) to the EECON register.
• EEBUSY flag in EECON is then set by hardware to indicate that programming is in progress and that the
EEPROM segment is not available for reading.
• The end of programming is indicated by a hardware clear of the EEBUSY flag.
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9.4. Read Data
The following procedure is used to read the data stored in the EEPROM memory:
• Set bit EEE of EECON register
• Load DPTR with the address to read
• Execute a MOVX A, @DPTR
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9.5. Registers
EECON (S:0D2h)
EEPROM Control Register
7
6
5
4
3
2
1
0
EEPL3
EEPL2
EEPL1
EEPL0
-
-
EEE
EEBUSY
Bit Number
Bit Mnemonic
7-4
EEPL3-0
3
-
Reserved
The value read from this bit is indeterminate. Do not set this bit.
2
-
Reserved
The value read from this bit is indeterminate. Do not set this bit.
1
EEE
0
EEBUSY
Description
Programming Launch command bits
Write 5Xh followed by AXh to EEPL to launch the programming.
Enable EEPROM Space bit
Set to map the EEPROM space during MOVX instructions (Write in the column latches)
Clear to map the XRAM space during MOVX.
Programming Busy flag
Set by hardware when programming is in progress.
Cleared by hardware when programming is done.
Can not be set or cleared by software.
Reset Value= XXXX XX00b
Not bit addressable
Figure 26. EECON Register
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10. In-System-Programming (ISP)
10.1. Introduction
With the implementation of the User ROM and the Boot ROM in Flash technology the T89C51AC2 allows the
system engineer the development of applications with a very high level of flexibility. This flexibility is based on
the possibility to alter the customer programming on all stages of a product’s life:
• During the final production phase, the 1st personalization of the product by parallel or serial charging of
the code in the User ROM and if wanted also a customized Boot loader in the Boot memory (Atmel will
provide also a standard Boot loader by default).
• After assembling of the product in its final, embedded position by serial mode via the UART.
This In-System-Programming (ISP) allows code modification over the total lifetime of the product.
Besides the default Boot loader Atmel will provide to the customer also all the needed Application-ProgrammingInterfaces (API) which are needed for the ISP. The API will be located also in the Boot memory.
This will allow the customer to have a full use of the 32 Kbyte user memory.
Two blocks flash memories are implemented (see Figure 27):
• Flash memory FM0:
containing 32 Kbytes of program memory organized in page of 128 bytes,
• Flash memory FM1:
2 Kbytes for default boot loader and Application Programming Interfaces (API).
The FM0 supports both, hardware (parallel) and software programming whereas FM1 supports only hardware
programming.
The ISP functions are assumed by:
• FCON register & bit ENBOOT in AUXR1 register,
• Software Boot Vector (SBV), which can be read and modified by using an API or the parallel programming
mode (see Figure 30)
The SBV is stored in XROW.
• The Fuse bit Boot Loader Jump Bit (BLJB) can be read and modified using an API or the parallel programming
mode.
The BLJB is located in the Hardware security byte (see Figure 32).
• The Extra Byte (EB) and Boot Status Byte (BSB) can be modified only by using API (see Figure 32).
EB is stored in XROW
The bit ENBOOT in AUXR1 register allows to map FM1 between address F800h and FFFFh of FM0.
The FM0 can be programed by:
- The Atmel boot loader, located by default in FM1.
- The user boot loader located in FM0
- The user boot loader located in FM1 in place of Atmel boot loader.
API contained in FM1 can be called by the user boot loader located in FM0 at the address [SBV]00h.
The user program simply calls the common entry point with appropriate parameters in FM1 to accomplish the
desired operation (all these methods will describe in Application Notes on api-description).
Boot Flash operations include: erase block, program byte or page, verify byte or page, program security lock bit,
etc. Indeed, Atmel provides the binary code of the default Flash boot loader.
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10.2. Flash Programming and Erasure
There are three methods of programming the Flash memory:
• The Atmel bootloader located in FM1 is activated by the application. Low level API routines (located in FM1)
to program FM0 will be used. The interface used for serial downloading to FM0 is the UART. API can be
called also by user’s bootloader located in FM0 at [SBV]00h.
• A further method exist in activating the Atmel boot loader by hardware activation.
• The FM0 can be programed also by the parallel mode using a programmer.
FFFFh
F800h
2 Kbytes IAP
bootloader
FM1
7FFFh
Custom
Boot Loader
FM1 mapped between FFFF and F800
when API called
[SBV]00h
32 Kbytes
Flash memory
FM0
0000h
Figure 27. Flash Memory Mapping
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10.2.1. Flash Parallel Programming
The three lock bits in Hardware byte are programmed according to Table, will provide different level of protection
for the on-chip code and data located in FM0 and FM1.
The only way for write this bits are the parallel mode.
Table 17. Program Lock bit
Program Lock Bits
Protection description
Security
level
LB0
LB1
LB2
1
U
U
U
No program lock features enabled. MOVC instruction executed from external program
memory returns non encrypted data.
2
P
U
U
MOVC instruction executed from external program memory are disabled from fetching
code bytes from internal memory, EA is sampled and latched on reset, and further
parallel programming of the Flash is disabled.
3
U
P
U
Same as 2, also verify through parallel programming interface is disabled.
4
U
U
P
Same as 3, also external execution is disabled.
Program Lock bits
U: unprogrammed
P: programmed
WARNING: Security level 2 and 3 should only be programmed after Flash and Core verification.
Program Lock bits
These security bits protect the code access through the parallel programming interface. They are set by default to
level 4.
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10.3 Boot Process
10.3.1. Software boot process example
Many algorithms can be used for the software boot process. Before describing them, some explanations are needed
for the utility of different flags and bytes available.
Boot Loader Jump Bit (BLJB):
- This bit indicates if on RESET the user wants jump on his application at address @0000h on FM0 or execute
the boot loader at address @F800h on FM1.
- BLJB = 0 on parts delivered with bootloader programmed.
- To read or modified this bit, the APIs are used.
Boot Vector Address (SBV):
- This byte contains the msb of the user boot loader address in FM0.
- The default value of SBV is FFh (no user boot loader in FM0).
- To read or modified this byte, the APIs are used.
Extra Byte (EB) & Boot Status Byte (BSB):
- These bytes are reserved for customer use.
- To read or modified this byte, the APIs are used.
Example of software boot process in FM1 (see Figure 29)
In this example the Extra Byte (EB) is a configuration bit which forces the user boot loader execution even on
the hardware condition.
10.3.2. Hardware boot process
At the falling edge of RESET, the bit ENBOOT in AUXR1 register is initialized with the value of Boot Loader
Jump Bit (BLJB).
Further at the falling edge of RESET if the following conditions (called Hardware condition) are detected:
• PSEN low,
• EA high,
• ALE high (or not connected).
FCON register is initialized with the value 00h and the program in FM1 can be executed.
The Hardware condition allows jump in bootloader (FM1) whatever BLJB value.
If no hardware condition is detected, the FCON register is initialized with the value F0h.
Check of the BLJB value.
• If bit BLJB is cleared (BLJB = 1):
User application in FM0 will be started at @0000h (standard reset).
• If bit BLJB is set (BLJB = 0):
Boot loader will be started at @F800h in FM1.
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bit ENBOOT in AUXR1 register
is initialized with BLJB.
RESET
ENBOOT = 1
PC = F800h
FCON = 00h
Hardware
Hardware
condition?
ENBOOT = 0
PC = 0000h
No
No
Yes
FCON = F0h
BLJB == 0
?
Yes
Software
USER APPLICATION
ENBOOT = 1
PC = F800h
Boot Loader
in FM1
Figure 28. Hardware Boot Process Algorithm
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bit ENBOOT in AUXR1 register
is initialized with BLJB (Fuse bit).
Hardware boot process
RESET
ENBOOT = 1
PC = F800h
FCON = 00h
Hardware
condition?
No
No
Yes
FCON = F0h
BLJB == 0
?
Yes
ENBOOT = 1
PC = F800h
USER APPLICATION
Software boot process
Yes
SBV < 3Fh
?
FCON == 00h
?
No
No
Yes
USER BOOT LOADER
DEFAULT BOOT LOADER
Figure 29. Example of Software Boot process
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10.4. 2 Application-Programming-Interface
Several Application Program Interface (API) calls are available for use by an application program to permit selective
erasing and programming of FLASH pages. All calls are made by functions.
All these APIs will be describe in an application note.
API CALL
PROGRAM DATA BYTE
PROGRAM DATA PAGE
PROGRAM EEPROM BYTE
ERASE BLOCK
ERASE BOOT VECTOR (SBV)
Description
Write a byte in flash memory
Write a page (128 bytes) in flash memory
Write a byte in Eeprom memory
Erase all flash memory
Erase the boot vector
PROGRAM BOOT VECTOR (SBV)
Write the boot vector
PROGRAM EXTRA BYTE (EB)
Write the extra byte
READ DATA BYTE
READ EEPROM BYTE
READ FAMILY CODE
READ MANUFACTURER CODE
READ PRODUCT NAME
READ REVISION NUMBER
READ STATUS BIT (BSB)
Read the status bit
READ BOOT VECTOR (SBV)
Read the boot vector
READ EXTRA BYTE (EB)
Read the extra byte
PROGRAM X2
READ X2
Write the hardware flag for X2 mode
Read the hardware flag for X2 mode
PROGRAM BLJB
Write the hardware flag BLJB
READ BLJB
Read the hardware flag BLJB
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10.5. Application remarks
• After loading a new program using by the boot loader, the BLJB bit must be set to allow user application to
start at RESET.
• A user bootloader can be mapped at address [SBV]00h. The byte SBV contains the high byte of the boot
address, and can be read and written by API.
• The API can be called during user application, without disabling interrupt.
The interrupts are disabled by some APIs, for complex operations.
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10.6. XROW Bytes
Mnemonic
Description
Default value
Address
SBV
Boot Vector Address
F8h
01h
SSB
Software Security Byte
FFh
05h
EB
Extra Byte
FFh
06h
Copy of the Manufacturer Code
58h
30h
Copy of the Device ID#1: Family code
D7h
31h
Copy of the Device ID#2:Memories size and
type
F7h
60h
Copy of the Device ID#3:Name and Revision FFh
61h
Table 18. Xrow mapping
SBV register
Software Boot Vector
7
6
5
4
3
2
1
0
ADD 7
ADD 6
ADD 5
ADD 4
ADD 3
ADD 2
ADD 1
ADD 0
Bit Number Bit Mnemonic
7-0
ADD7:0
Description
MSB of user boot loader address location
Default value after erasing chip: FFh
NOTE:
Only accessed by the API or in the parallel programming mode.
Figure 30. SBV Register
EB register
EXTRA BYTE
7
6
5
4
3
2
1
0
-
-
-
-
-
-
-
-
Bit Number Bit Mnemonic
7-0
-
Description
User definition
Default value after erasing chip: FFh
NOTE:
TOnly accessed by the API or in the parallel programming mode.
Figure 31. EB Register
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10.7. Hardware Byte
7
6
5
4
3
2
1
0
X2B
BLJB
-
-
-
LB2
LB1
LB0
Bit Number Bit Mnemonic
Description
7
X2B
X2 Bit
Set this bit to start in standard mode
Clear this bit to start in X2 mode.
6
BLJB
Boot Loader JumpBit
Clear (=1)this bit to start the user’s application on next RESET (@0000h) located in FM0,
Set (=0)this bit to start the boot loader(@F800h) located in FM1.
5-3
-
2-0
LB2:0
Reserved
The value read from these bits are indeterminate.
Lock Bits
Default value after erasing chip: FFh
NOTE:
Only the 4 MSB bits can be access by software.
The 4 LSB bits can only be access by parallel mode.
Figure 32. Hardware byte
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11. Serial I/O Port
The T89C51AC2 I/O serial port is compatible with the I/O serial port in the 80C52.
It provides both synchronous and asynchronous communication modes. It operates as a Universal Asynchronous
Receiver and Transmitter (UART) in three full-duplex modes (Modes 1, 2 and 3). Asynchronous transmission and
reception can occur simultaneously and at different baud rates
Serial I/O port includes the following enhancements:
• Framing error detection
• Automatic address recognition
IB Bus
Write SBUF
Read SBUF
SBUF
Receiver
SBUF
Transmitter
TXD
Load SBUF
Mode 0 Transmit
Receive
Shift register
RXD
Serial Port
Interrupt Request
RI
TI
SCONI/O Port Block Diagram
Figure 33. Serial
11.1. Framing Error Detection
Framing bit error detection is provided for the three asynchronous modes. To enable the framing bit error detection
feature, set SMOD0 bit in PCON register.
SM0/FE SM1
SM2
REN
TB8
RB8
TI
RI
Set FE bit if stop bit is 0 (framing error)
SM0 to UART mode control
SMOD1 SMOD0
-
POF
GF1
GF0
PD
IDL
To UART framing error control
Figure 34. Framing Error Block Diagram
When this feature is enabled, the receiver checks each incoming data frame for a valid stop bit. An invalid stop
bit may result from noise on the serial lines or from simultaneous transmission by two CPUs. If a valid stop bit
is not found, the Framing Error bit (FE) in SCON register bit is set.
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The software may examine the FE bit after each reception to check for data errors. Once set, only software or a
reset clears the FE bit. Subsequently received frames with valid stop bits cannot clear the FE bit. When the FE
feature is enabled, RI rises on the stop bit instead of the last data bit (See Figure 35. and Figure 36.).
RXD
D0
D1
D2
Start
bit
D3
D4
D5
D6
D7
Data byte
Stop
bit
RI
SMOD0=X
FE
SMOD0=1
Figure 35. UART Timing in Mode 1
RXD
D0
Start
bit
D1
D2
D3
D4
D5
D6
Data byte
D7
D8
NinthStop
bit bit
RI
SMOD0=0
RI
SMOD0=1
FE
SMOD0=1
Figure 36. UART Timing in Modes 2 and 3
11.2. Automatic Address Recognition
The automatic address recognition feature is enabled when the multiprocessor communication feature is enabled
(SM2 bit in SCON register is set).
Implemented in the hardware, automatic address recognition enhances the multiprocessor communication feature
by allowing the serial port to examine the address of each incoming command frame. Only when the serial port
recognizes its own address will the receiver set the RI bit in the SCON register to generate an interrupt. This
ensures that the CPU is not interrupted by command frames addressed to other devices.
If necessary, you can enable the automatic address recognition feature in mode 1. In this configuration, the stop
bit takes the place of the ninth data bit. Bit RI is set only when the received command frame address matches the
device’s address and is terminated by a valid stop bit.
To support automatic address recognition, a device is identified by a given address and a broadcast address.
NOTE: The multiprocessor communication and automatic address recognition features cannot be enabled in mode 0 (i.e. setting SM2 bit in SCON
register in mode 0 has no effect).
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11.3. Given Address
Each device has an individual address that is specified in the SADDR register; the SADEN register is a mask byte
that contains don’t-care bits (defined by zeros) to form the device’s given address. The don’t-care bits provide the
flexibility to address one or more slaves at a time. The following example illustrates how a given address is formed.
To address a device by its individual address, the SADEN mask byte must be 1111 1111b.
For example:
SADDR
SADEN
Given
0101 0110b
1111 1100b
0101 01XXb
Here is an example of how to use given addresses to address different slaves:
Slave A:
SADDR
SADEN
Given
1111 0001b
1111 1010b
1111 0X0Xb
Slave B:
SADDR
SADEN
Given
1111 0011b
1111 1001b
1111 0XX1b
Slave C:
SADDR
SADEN
Given
1111 0010b
1111 1101b
1111 00X1b
The SADEN byte is selected so that each slave may be addressed separately.
For slave A, bit 0 (the LSB) is a don’t-care bit; for slaves B and C, bit 0 is a 1. To communicate with slave A
only, the master must send an address where bit 0 is clear (e.g. 1111 0000b).
For slave A, bit 1 is a 0; for slaves B and C, bit 1 is a don’t care bit. To communicate with slaves A and B, but
not slave C, the master must send an address with bits 0 and 1 both set (e.g. 1111 0011b).
To communicate with slaves A, B and C, the master must send an address with bit 0 set, bit 1 clear, and bit 2
clear (e.g. 1111 0001b).
11.4. Broadcast Address
A broadcast address is formed from the logical OR of the SADDR and SADEN registers with zeros defined as
don’t-care bits, e.g.:
SADDR
SADEN
SADDR OR SADEN
0101 0110b
1111 1100b
1111 111Xb
The use of don’t-care bits provides flexibility in defining the broadcast address, however in most applications, a
broadcast address is FFh. The following is an example of using broadcast addresses:
Slave A:
SADDR
SADEN
Given
1111 0001b
1111 1010b
1111 1X11b,
Slave B:
SADDR
SADEN
Given
1111 0011b
1111 1001b
1111 1X11B,
Slave C:
SADDR=
SADEN
Given
1111 0010b
1111 1101b
1111 1111b
For slaves A and B, bit 2 is a don’t care bit; for slave C, bit 2 is set. To communicate with all of the slaves, the
master must send an address FFh. To communicate with slaves A and B, but not slave C, the master can send
and address FBh.
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11.5. REGISTERS
SCON (S:98h)
Serial Control Register
7
6
5
4
3
2
1
0
FE/SM0
SM1
SM2
REN
TB8
RB8
TI
RI
Bit Number Bit Mnemonic
7
FE
Description
Framing Error bit (SMOD0=1)
Clear to reset the error state, not cleared by a valid stop bit.
Set by hardware when an invalid stop bit is detected.
SM0
Serial port Mode bit 0 (SMOD0=0)
Refer to SM1 for serial port mode selection.
6
SM1
Serial port Mode bit 1
SM0
SM1
0
0
0
1
1
0
1
1
5
SM2
Serial port Mode 2 bit / Multiprocessor Communication Enable bit
Clear to disable multiprocessor communication feature.
Set to enable multiprocessor communication feature in mode 2 and 3.
4
REN
Reception Enable bit
Clear to disable serial reception.
Set to enable serial reception.
3
TB8
Transmitter Bit 8 / Ninth bit to transmit in modes 2 and 3
Clear to transmit a logic 0 in the 9th bit.
Set to transmit a logic 1 in the 9th bit.
2
RB8
Receiver Bit 8 / Ninth bit received in modes 2 and 3
Cleared by hardware if 9th bit received is a logic 0.
Set by hardware if 9th bit received is a logic 1.
ModeBaud Rate
Shift RegisterFXTAL/12
8-bit UARTVariable
9-bit UARTFXTAL/64 or FXTAL/32
9-bit UARTVariable
1
TI
Transmit Interrupt flag
Clear to acknowledge interrupt.
Set by hardware at the end of the 8th bit time in mode 0 or at the beginning of the stop bit in the other
modes.
0
RI
Receive Interrupt flag
Clear to acknowledge interrupt.
Set by hardware at the end of the 8th bit time in mode 0, see Figure 35. and Figure 36. in the other modes.
Reset Value = 0000 0000b
Bit addressable
Figure 37. SCON Register
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SADEN (S:B9h)
Slave Address Mask Register
7
6
5
4
3
Bit Number Bit Mnemonic
7-0
2
1
0
2
1
0
2
1
0
Description
Mask Data for Slave Individual Address
Reset Value = 0000 0000b
Not bit addressable
Figure 38. SADEN Register
SADDR (S:A9h)
Slave Address Register
7
6
5
4
3
Bit Number Bit Mnemonic
7-0
Description
Slave Individual Address
Reset Value = 0000 0000b
Not bit addressable
Figure 39. SADDR Register
SBUF (S:99h)
Serial Data Buffer
7
6
5
4
Bit Number Bit Mnemonic
7-0
3
Description
Data sent/received by Serial I/O Port
Reset Value = 0000 0000b
Not bit addressable
Figure 40. SBUF Register
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PCON (S:87h)
Power Control Register
7
6
5
4
3
2
1
0
SMOD1
SMOD0
-
POF
GF1
GF0
PD
IDL
Bit Number Bit Mnemonic
Description
7
SMOD1
Serial port Mode bit 1
Set to select double baud rate in mode 1, 2 or 3.
6
SMOD0
Serial port Mode bit 0
Clear to select SM0 bit in SCON register.
Set to select FE bit in SCON register.
5
-
4
POF
Power-Off Flag
Clear to recognize next reset type.
Set by hardware when VCC rises from 0 to its nominal voltage. Can also be set by software.
3
GF1
General purpose Flag
Cleared by user for general purpose usage.
Set by user for general purpose usage.
2
GF0
General purpose Flag
Cleared by user for general purpose usage.
Set by user for general purpose usage.
1
PD
Power-Down mode bit
Cleared by hardware when reset occurs.
Set to enter power-down mode.
0
IDL
Idle mode bit
Clear by hardware when interrupt or reset occurs.
Set to enter idle mode.
Reserved
The value read from this bit is indeterminate. Do not set this bit.
Reset Value = 00X1 0000b
Not bit addressable
Figure 41. PCON Register
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12. Timers/Counters
12.1. Introduction
The T89C51AC2 implements two general-purpose, 16-bit Timers/Counters. They are identified as Timer 0 and
Timer 1, and can be independently configured to operate in a variety of modes as a Timer or as an event Counter.
When operating as a Timer, the Timer/Counter runs for a programmed length of time, then issues an interrupt
request. When operating as a Counter, the Timer/Counter counts negative transitions on an external pin. After a
preset number of counts, the Counter issues an interrupt request.
The various operating modes of each Timer/Counter are described in the following sections.
12.2. Timer/Counter Operations
For instance, a basic operation is Timer registers THx and TLx (x= 0, 1) connected in cascade to form a 16-bit
Timer. Setting the run control bit (TRx) in TCON register (see Figure 47) turns the Timer on by allowing the
selected input to increment TLx. When TLx overflows it increments THx; when THx overflows it sets the Timer
overflow flag (TFx) in TCON register. Setting the TRx does not clear the THx and TLx Timer registers. Timer
registers can be accessed to obtain the current count or to enter preset values. They can be read at any time but
TRx bit must be cleared to preset their values, otherwise the behavior of the Timer/Counter is unpredictable.
The C/Tx# control bit selects Timer operation or Counter operation by selecting the divided-down peripheral clock
or external pin Tx as the source for the counted signal. TRx bit must be cleared when changing the mode of
operation, otherwise the behavior of the Timer/Counter is unpredictable.
For Timer operation (C/Tx#= 0), the Timer register counts the divided-down peripheral clock. The Timer register
is incremented once every peripheral cycle (6 peripheral clock periods). The Timer clock rate is FPER / 6, i.e.
FOSC / 12 in standard mode or FOSC / 6 in X2 mode.
For Counter operation (C/Tx#= 1), the Timer register counts the negative transitions on the Tx external input pin.
The external input is sampled every peripheral cycles. When the sample is high in one cycle and low in the next
one, the Counter is incremented. Since it takes 2 cycles (12 peripheral clock periods) to recognize a negative
transition, the maximum count rate is FPER / 12, i.e. FOSC / 24 in standard mode or FOSC / 12 in X2 mode. There
are no restrictions on the duty cycle of the external input signal, but to ensure that a given level is sampled at
least once before it changes, it should be held for at least one full peripheral cycle.
12.3. Timer 0
Timer 0 functions as either a Timer or event Counter in four modes of operation. Figure 42 to Figure 45 show the
logical configuration of each mode.
Timer 0 is controlled by the four lower bits of TMOD register (see Figure 48) and bits 0, 1, 4 and 5 of TCON
register (see Figure 47). TMOD register selects the method of Timer gating (GATE0), Timer or Counter operation
(T/C0#) and mode of operation (M10 and M00). TCON register provides Timer 0 control functions: overflow flag
(TF0), run control bit (TR0), interrupt flag (IE0) and interrupt type control bit (IT0).
For normal Timer operation (GATE0= 0), setting TR0 allows TL0 to be incremented by the selected input. Setting
GATE0 and TR0 allows external pin INT0# to control Timer operation.
Timer 0 overflow (count rolls over from all 1s to all 0s) sets TF0 flag generating an interrupt request.
It is important to stop Timer/Counter before changing mode.
12.3.1. Mode 0 (13-bit Timer)
Mode 0 configures Timer 0 as an 13-bit Timer which is set up as an 8-bit Timer (TH0 register) with a modulo
32 prescaler implemented with the lower five bits of TL0 register (see Figure 42). The upper three bits of TL0
register are indeterminate and should be ignored. Prescaler overflow increments TH0 register.
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PERIPH
CLOCK
÷6
0
THx
(8 bits)
1
TLx
(5 bits)
Overflow
TFx
TCON reg
Timer x
Interrupt
Request
Tx
C/Tx#
TMOD reg
INTx#
GATEx
TRx
TMOD reg
TCON reg
Figure 42. Timer/Counter x (x= 0 or 1) in Mode 0
12.3.2. Mode 1 (16-bit Timer)
Mode 1 configures Timer 0 as a 16-bit Timer with TH0 and TL0 registers connected in cascade (see Figure 43).
The selected input increments TL0 register.
PERIPH
CLOCK
÷6
0
THx
(8 bits)
1
TLx
(8 bits)
Overflow
TFx
TCON reg
Timer x
Interrupt
Request
Tx
C/Tx#
TMOD reg
INTx#
GATEx
TRx
TMOD reg
TCON reg
Figure 43. Timer/Counter x (x= 0 or 1) in Mode 1
12.3.3. Mode 2 (8-bit Timer with Auto-Reload)
Mode 2 configures Timer 0 as an 8-bit Timer (TL0 register) that automatically reloads from TH0 register (see
Figure 44). TL0 overflow sets TF0 flag in TCON register and reloads TL0 with the contents of TH0, which is
preset by software. When the interrupt request is serviced, hardware clears TF0. The reload leaves TH0 unchanged.
The next reload value may be changed at any time by writing it to TH0 register.
PERIPH
CLOCK
÷6
0
TLx
(8 bits)
1
Overflow
TFx
TCON reg
Timer x
Interrupt
Request
Tx
C/Tx#
TMOD reg
INTx#
GATEx
TMOD reg
TRx
THx
(8 bits)
TCON reg
Figure 44. Timer/Counter x (x= 0 or 1) in Mode 2
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12.3.4. Mode 3 (Two 8-bit Timers)
Mode 3 configures Timer 0 such that registers TL0 and TH0 operate as separate 8-bit Timers (see Figure 45). This
mode is provided for applications requiring an additional 8-bit Timer or Counter. TL0 uses the Timer 0 control
bits C/T0# and GATE0 in TMOD register, and TR0 and TF0 in TCON register in the normal manner. TH0 is
locked into a Timer function (counting FPER /6) and takes over use of the Timer 1 interrupt (TF1) and run control
(TR1) bits. Thus, operation of Timer 1 is restricted when Timer 0 is in mode 3.
PERIPH
CLOCK
÷6
0
1
TL0
(8 bits)
Overflow
TH0
(8 bits)
Overflow
TF0
TCON.5
Timer 0
Interrupt
Request
T0
C/T0#
TMOD.2
INT0#
GATE0
TMOD.3
PERIPH
CLOCK
TR0
TCON.4
÷6
TF1
TCON.7
Timer 1
Interrupt
Request
TR1
TCON.6
Figure 45. Timer/Counter 0 in Mode 3: Two 8-bit Counters
12.4. Timer 1
Timer 1 is identical to Timer 0 excepted for Mode 3 which is a hold-count mode. Following comments help to
understand the differences:
• Timer 1 functions as either a Timer or event Counter in three modes of operation. Figure 42 to Figure 44 show
the logical configuration for modes 0, 1, and 2. Timer 1’s mode 3 is a hold-count mode.
• Timer 1 is controlled by the four high-order bits of TMOD register (see Figure 48) and bits 2, 3, 6 and 7 of
TCON register (see Figure 47). TMOD register selects the method of Timer gating (GATE1), Timer or Counter
operation (C/T1#) and mode of operation (M11 and M01). TCON register provides Timer 1 control functions:
overflow flag (TF1), run control bit (TR1), interrupt flag (IE1) and interrupt type control bit (IT1).
• Timer 1 can serve as the Baud Rate Generator for the Serial Port. Mode 2 is best suited for this purpose.
• For normal Timer operation (GATE1= 0), setting TR1 allows TL1 to be incremented by the selected input.
Setting GATE1 and TR1 allows external pin INT1# to control Timer operation.
• Timer 1 overflow (count rolls over from all 1s to all 0s) sets the TF1 flag generating an interrupt request.
• When Timer 0 is in mode 3, it uses Timer 1’s overflow flag (TF1) and run control bit (TR1). For this situation,
use Timer 1 only for applications that do not require an interrupt (such as a Baud Rate Generator for the Serial
Port) and switch Timer 1 in and out of mode 3 to turn it off and on.
• It is important to stop Timer/Counter before changing mode.
12.4.1. Mode 0 (13-bit Timer)
Mode 0 configures Timer 1 as a 13-bit Timer, which is set up as an 8-bit Timer (TH1 register) with a modulo32 prescaler implemented with the lower 5 bits of the TL1 register (see Figure 42). The upper 3 bits of TL1 register
are ignored. Prescaler overflow increments TH1 register.
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12.4.2. Mode 1 (16-bit Timer)
Mode 1 configures Timer 1 as a 16-bit Timer with TH1 and TL1 registers connected in cascade (see Figure 43).
The selected input increments TL1 register.
12.4.3. Mode 2 (8-bit Timer with Auto-Reload)
Mode 2 configures Timer 1 as an 8-bit Timer (TL1 register) with automatic reload from TH1 register on overflow
(see Figure 44). TL1 overflow sets TF1 flag in TCON register and reloads TL1 with the contents of TH1, which
is preset by software. The reload leaves TH1 unchanged.
12.4.4. Mode 3 (Halt)
Placing Timer 1 in mode 3 causes it to halt and hold its count. This can be used to halt Timer 1 when TR1 run
control bit is not available i.e. when Timer 0 is in mode 3.
12.5. Interrupt
Each Timer handles one interrupt source that is the timer overflow flag TF0 or TF1. This flag is set every time
an overflow occurs. Flags are cleared when vectoring to the Timer interrupt routine. Interrupts are enabled by
setting ETx bit in IEN0 register. This assumes interrupts are globally enabled by setting EA bit in IEN0 register.
Timer 0
Interrupt Request
TF0
TCON.5
ET0
IEN0.1
Timer 1
Interrupt Request
TF1
TCON.7
ET1
IEN0.3
Figure 46. Timer Interrupt System
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12.6. Registers
TCON (S:88h)
Timer/Counter Control Register.
7
6
5
4
3
2
1
0
TF1
TR1
TF0
TR0
IE1
IT1
IE0
IT0
Bit Number Bit Mnemonic
Description
7
TF1
Timer 1 Overflow Flag
Cleared by hardware when processor vectors to interrupt routine.
Set by hardware on Timer/Counter overflow, when Timer 1 register overflows.
6
TR1
Timer 1 Run Control Bit
Clear to turn off Timer/Counter 1.
Set to turn on Timer/Counter 1.
5
TF0
Timer 0 Overflow Flag
Cleared by hardware when processor vectors to interrupt routine.
Set by hardware on Timer/Counter overflow, when Timer 0 register overflows.
4
TR0
Timer 0 Run Control Bit
Clear to turn off Timer/Counter 0.
Set to turn on Timer/Counter 0.
3
IE1
Interrupt 1 Edge Flag
Cleared by hardware when interrupt is processed if edge-triggered (see IT1).
Set by hardware when external interrupt is detected on INT1# pin.
2
IT1
Interrupt 1 Type Control Bit
Clear to select low level active (level triggered) for external interrupt 1 (INT1#).
Set to select falling edge active (edge triggered) for external interrupt 1.
1
IE0
Interrupt 0 Edge Flag
Cleared by hardware when interrupt is processed if edge-triggered (see IT0).
Set by hardware when external interrupt is detected on INT0# pin.
0
IT0
Interrupt 0 Type Control Bit
Clear to select low level active (level triggered) for external interrupt 0 (INT0#).
Set to select falling edge active (edge triggered) for external interrupt 0.
Reset Value= 0000 0000b
Figure 47. TCON Register
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TMOD (S:89h)
Timer/Counter Mode Control Register.
7
6
5
4
3
2
1
0
GATE1
C/T1#
M11
M01
GATE0
C/T0#
M10
M00
Bit Number Bit Mnemonic
7
GATE1
6
C/T1#
5
M11
4
M01
3
GATE0
2
C/T0#
1
M10
0
M00
Description
Timer 1 Gating Control Bit
Clear to enable Timer 1 whenever TR1 bit is set.
Set to enable Timer 1 only while INT1# pin is high and TR1 bit is set.
Timer 1 Counter/Timer Select Bit
Clear for Timer operation: Timer 1 counts the divided-down system clock.
Set for Counter operation: Timer 1 counts negative transitions on external pin T1.
Timer 1 Mode Select Bits
M11
M01
Operating mode
0
0
Mode 0: 8-bit Timer/Counter (TH1) with 5-bit prescaler (TL1).
0
1
Mode 1: 16-bit Timer/Counter.
1
0
Mode 2: 8-bit auto-reload Timer/Counter (TL1). Reloaded from TH1 at overflow.
1
1
Mode 3: Timer 1 halted. Retains count.
Timer 0 Gating Control Bit
Clear to enable Timer 0 whenever TR0 bit is set.
Set to enable Timer/Counter 0 only while INT0# pin is high and TR0 bit is set.
Timer 0 Counter/Timer Select Bit
Clear for Timer operation: Timer 0 counts the divided-down system clock.
Set for Counter operation: Timer 0 counts negative transitions on external pin T0.
Timer 0 Mode Select Bit
M10
M00
Operating mode
0
0
Mode 0: 8-bit Timer/Counter (TH0) with 5-bit prescaler (TL0).
0
1
Mode 1: 16-bit Timer/Counter.
1
0
Mode 2: 8-bit auto-reload Timer/Counter (TL0). Reloaded from TH0 at overflow.
1
1
Mode 3: TL0 is an 8-bit Timer/Counter.
TH0 is an 8-bit Timer using Timer 1’s TR0 and TF0 bits.
Reset Value= 0000 0000b
Figure 48. TMOD Register
TH0 (S:8Ch)
Timer 0 High Byte Register.
7
6
5
4
Bit Number Bit Mnemonic
7:0
3
2
1
0
Description
High Byte of Timer 0.
Reset Value= 0000 0000b
Figure 49. TH0 Register
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TL0 (S:8Ah)
Timer 0 Low Byte Register.
7
6
5
4
3
Bit Number Bit Mnemonic
7:0
2
1
0
2
1
0
2
1
0
Description
Low Byte of Timer 0.
Reset Value= 0000 0000b
Figure 50. TL0 Register
TH1 (S:8Dh)
Timer 1 High Byte Register.
7
6
5
4
3
Bit Number Bit Mnemonic
7:0
Description
High Byte of Timer 1.
Reset Value= 0000 0000b
Figure 51. TH1 Register
TL1 (S:8Bh)
Timer 1 Low Byte Register.
7
6
5
4
Bit Number Bit Mnemonic
7:0
3
Description
Low Byte of Timer 1.
Reset Value= 0000 0000b
Figure 52. TL1 Register
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13. Timer 2
13.1. Introduction
The T89C51AC2 timer 2 is compatible with timer 2 in the 80C52.
It is a 16-bit timer/counter: the count is maintained by two eight-bit timer registers, TH2 and TL2 that are cascadeconnected. It is controlled by T2CON register (See Table 55) and T2MOD register (See Table 56). Timer 2 operation
is similar to Timer 0 and Timer 1. C/T2 selects FOSC/6 (timer operation) or external pin T2 (counter operation)
as timer register input. Setting TR2 allows TL2 to be incremented by the selected input.
Timer 2 includes the following enhancements:
• Auto-reload mode (up or down counter)
• Programmable clock-output
13.2. Auto-Reload Mode
The auto-reload mode configures timer 2 as a 16-bit timer or event counter with automatic reload. This feature is
controlled by the DCEN bit in T2MOD register (See Table 56). Setting the DCEN bit enables timer 2 to count up
or down as shown in Figure 53. In this mode the T2EX pin controls the counting direction.
When T2EX is high, timer 2 up-counts. Timer overflow occurs at FFFFh which sets the TF2 flag and generates
an interrupt request. The overflow also causes the 16-bit value in RCAP2H and RCAP2L registers to be loaded
into the timer registers TH2 and TL2.
When T2EX is low, timer 2 down-counts. Timer underflow occurs when the count in the timer registers TH2 and
TL2 equals the value stored in RCAP2H and RCAP2L registers. The underflow sets TF2 flag and reloads FFFFh
into the timer registers.
The EXF2 bit toggles when timer 2 overflow or underflow, depending on the direction of the count. EXF2 does
not generate an interrupt. This bit can be used to provide 17-bit resolution.
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FT2
CLOCK
:6
0
1
TR2
T2CON.2
CT/2
T2CON.1
T2
(DOWN COUNTING RELOAD VALUE)
FFh
FFh
(8-bit)
(8-bit)
T2EX:
1=UP
2=DOWN
TOGGLE
T2CONreg
EXF2
TL2
TH2
(8-bit)
(8-bit)
RCAP2L
(8-bit)
TF2
TIMER 2
INTERRUPT
T2CONreg
RCAP2H
(8-bit)
(UP COUNTING RELOAD VALUE)
Figure 53. Auto-Reload Mode Up/Down Counter
13.3. Programmable Clock-Output
In clock-out mode, timer 2 operates as a 50%-duty-cycle, programmable clock generator (See Figure 54). The input
clock increments TL2 at frequency FOSC/2. The timer repeatedly counts to overflow from a loaded value. At
overflow, the contents of RCAP2H and RCAP2L registers are loaded into TH2 and TL2. In this mode, timer 2
overflows do not generate interrupts. The formula gives the clock-out frequency depending on the system oscillator
frequency and the value in the RCAP2H and RCAP2L registers:
F
× 2 x2
osc
Clock – OutFrequency = -------------------------------------------------------------------------------------4 × ( 65536 – RCAP2H ⁄ RCAP2L )
NOTE: X2 bit is located in CKCON register.
In X2 mode, FOSC=FXTAL. In standard mode, FOSC=FXTAL/2.
For a 16 MHz system clock, timer 2 has a programmable frequency range of 61 Hz (FOSC/216) to 4 MHz (FOSC/
4). The generated clock signal is brought out to T2 pin (P1.0).
Timer 2 is programmed for the clock-out mode as follows:
• Set T2OE bit in T2MOD register.
• Clear C/T2 bit in T2CON register.
• Determine the 16-bit reload value from the formula and enter it in RCAP2H/RCAP2L registers.
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• Enter a 16-bit initial value in timer registers TH2/TL2. It can be the same as the reload value or different
depending on the application.
• To start the timer, set TR2 run control bit in T2CON register.
It is possible to use timer 2 as a baud rate generator and a clock generator simultaneously. For this configuration,
the baud rates and clock frequencies are not independent since both functions use the values in the RCAP2H and
RCAP2L registers.
FT2
CLOCK
0
1
TR2
T2CON.2
CT/2
TL2
(8-bit)
TH2
(8-bit)
T2CON.1
OVERFLOW
RCAP2 RCAP2
(8-bit) (8-bit)
T2
1
0
:2
C/T2
T2CON reg
T2OE
T2MOD reg
T2EX
EXF2
EXEN2
T2CON reg
TIMER 2
INTERRUPT
T2CON reg
Figure 54. Clock-Out Mode
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13.4. Registers
T2CON (S:C8h)
Timer 2 Control Register
7
6
5
4
3
2
1
0
TF2
EXF2
RCLK
TCLK
EXEN2
TR2
C/T2#
CP/RL2#
Bit Number Bit Mnemonic
7
TF2
Description
Timer 2 overflow Flag
TF2 is not set if RCLK=1 or TCLK = 1.
Must be cleared by software.
Set by hardware on timer 2 overflow.
6
EXF2
Timer 2 External Flag
Set when a capture or a reload is caused by a negative transition on T2EX pin if EXEN2=1.
Set to cause the CPU to vector to timer 2 interrupt routine when timer 2 interrupt is enabled.
Must be cleared by software.
5
RCLK
Receive Clock bit
Clear to use timer 1 overflow as receive clock for serial port in mode 1 or 3.
Set to use timer 2 overflow as receive clock for serial port in mode 1 or 3.
4
TCLK
Transmit Clock bit
Clear to use timer 1 overflow as transmit clock for serial port in mode 1 or 3.
Set to use timer 2 overflow as transmit clock for serial port in mode 1 or 3.
3
EXEN2
Timer 2 External Enable bit
Clear to ignore events on T2EX pin for timer 2 operation.
Set to cause a capture or reload when a negative transition on T2EX pin is detected, if timer 2 is not used to
clock the serial port.
2
TR2
1
C/T2#
0
CP/RL2#
Timer 2 Run control bit
Clear to turn off timer 2.
Set to turn on timer 2.
Timer/Counter 2 select bit
Clear for timer operation (input from internal clock system: FOSC).
Set for counter operation (input from T2 input pin).
Timer 2 Capture/Reload bit
If RCLK=1 or TCLK=1, CP/RL2# is ignored and timer is forced to auto-reload on timer 2 overflow.
Clear to auto-reload on timer 2 overflows or negative transitions on T2EX pin if EXEN2=1.
Set to capture on negative transitions on T2EX pin if EXEN2=1.
Reset Value = 0000 0000b
Bit addressable
Figure 55. T2CON Register
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T2MOD (S:C9h)
Timer 2 Mode Control Register
7
6
5
4
3
2
1
0
-
-
-
-
-
-
T2OE
DCEN
Bit Number Bit Mnemonic
Description
7
-
Reserved
The value read from this bit is indeterminate. Do not set this bit.
6
-
Reserved
The value read from this bit is indeterminate. Do not set this bit.
5
-
Reserved
The value read from this bit is indeterminate. Do not set this bit.
4
-
Reserved
The value read from this bit is indeterminate. Do not set this bit.
3
-
Reserved
The value read from this bit is indeterminate. Do not set this bit.
2
-
Reserved
The value read from this bit is indeterminate. Do not set this bit.
1
T2OE
Timer 2 Output Enable bit
Clear to program P1.0/T2 as clock input or I/O port.
Set to program P1.0/T2 as clock output.
0
DCEN
Down Counter Enable bit
Clear to disable timer 2 as up/down counter.
Set to enable timer 2 as up/down counter.
Reset Value = XXXX XX00b
Not bit addressable
Figure 56. T2MOD Register
TH2 (S:CDh)
Timer 2 High Byte Register
7
6
5
4
3
2
1
0
-
-
-
-
-
-
-
-
Bit Number Bit Mnemonic
7-0
Description
High Byte of Timer 2.
Reset Value = 0000 0000b
Not bit addressable
Figure 57. TH2 Register
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TL2 (S:CCh)
Timer 2 Low Byte Register
7
6
5
4
3
2
1
0
-
-
-
-
-
-
-
-
Bit Number Bit Mnemonic
7-0
Description
Low Byte of Timer 2.
Reset Value = 0000 0000b
Not bit addressable
Figure 58. TL2 Register
RCAP2H (S:CBh)
Timer 2 Reload/Capture High Byte Register
7
6
5
4
3
2
1
0
-
-
-
-
-
-
-
-
Bit Number Bit Mnemonic
7-0
Description
High Byte of Timer 2 Reload/Capture.
Reset Value = 0000 0000b
Not bit addressable
Figure 59. RCAP2H Register
RCAP2L (S:CAh)
Timer 2 Reload/Capture Low Byte Register
7
6
5
4
3
2
1
0
-
-
-
-
-
-
-
-
Bit Number Bit Mnemonic
7-0
Description
Low Byte of Timer 2 Reload/Capture.
Reset Value = 0000 0000b
Not bit addressable
Figure 60. RCAP2L Register
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14. WatchDog Timer
14.1. Introduction
T89C51AC2 contains a powerful programmable hardware WatchDog Timer (WDT) that automatically resets the
chip if it software fails to reset the WDT before the selected time interval has elapsed. It permits large Time-Out
ranking from 16ms to 2s @Fosc = 12MHz.
This WDT consist of a 14-bit counter plus a 7-bit programmable counter, a WatchDog Timer reset register
(WDTRST) and a WatchDog Timer programming (WDTPRG) register. When exiting reset, the WDT is -by defaultdisable. To enable the WDT, the user has to write the sequence 1EH and E1H into WDTRST register. When the
WatchDog Timer is enabled, it will increment every machine cycle while the oscillator is running and there is no
way to disable the WDT except through reset (either hardware reset or WDT overflow reset). When WDT overflows,
it will generate an output RESET pulse at the RST pin. The RESET pulse duration is 96xTOSC, where TOSC=1/
FOSC. To make the best use of the WDT, it should be serviced in those sections of code that will periodically be
executed within the time required to prevent a WDT reset.
Fwd
CLOCK
÷ PS
CPU and Peripheral
Clock
÷6
Decoder
RESET
WR
Control
WDTRST
Enable
14-bit COUNTER
7-bit COUNTER
PERIPHERAL CLOCK
Outputs
-
-
-
-
-
2
1
0
RESET
Figure 61. WatchDog Timer
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14.2. WatchDog Programming
The three lower bits (S0, S1, S2) located into WDTPRG register permits to program the WDT duration.
Table 19. Machine Cycle Count
S2
S1
S0
Machine Cycle Count
0
0
0
214 - 1
0
0
1
215 - 1
0
1
0
216 - 1
0
1
1
217 - 1
1
0
0
218 - 1
1
0
1
219 - 1
1
1
0
220 - 1
1
1
1
221 - 1
To compute WD Time-Out, the following formula is applied:
F XTAL
FTime – Out = -----------------------------------------------------------14
Svalue
12 × ( ( 2 × 2
) – 1)
Note: Svalue represents the decimal value of (S2 S1 S0)
Find Hereafter computed Time-Out value for FoscXTAL = 12MHz
Table 20. Time-Out Computation
S2
S1
S0
Fosc=12MHz
Fosc=16MHz
0
0
0
16.38 ms
12.28 ms
9.82 ms
0
0
1
32.77 ms
24.57 ms
19.66 ms
0
1
0
65.54 ms
49.14 ms
39.32 ms
0
1
1
131.07 ms
98.28 ms
78.64 ms
1
0
0
262.14 ms
196.56 ms
157.28 ms
1
0
1
524.29 ms
393.12 ms
314.56 ms
1
1
0
1.05 s
786.24 ms
629.12 ms
1
1
1
2.10 s
1.57 s
1.25 ms
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14.3. WatchDog Timer during Power down mode and Idle
In Power Down mode the oscillator stops, which means the WDT also stops. While in Power Down mode the
user does not need to service the WDT. There are 2 methods of exiting Power Down mode: by a hardware reset
or via a level activated external interrupt which is enabled prior to entering Power Down mode. When Power
Down is exited with hardware reset, servicing the WDT should occur as it normally does whenever T89C51AC2
is reset. Exiting Power Down with an interrupt is significantly different. The interrupt is held low long enough for
the oscillator to stabilize. When the interrupt is brought high, the interrupt is serviced. To prevent the WDT from
resetting the device while the interrupt pin is held low, the WDT is not started until the interrupt is pulled high.
It is suggested that the WDT be reset during the interrupt service for the interrupt used to exit Power Down.
To ensure that the WDT does not overflow within a few states of exiting of powerdown, it is best to reset the
WDT just before entering powerdown.
In the Idle mode, the oscillator continues to run. To prevent the WDT from resetting T89C51AC2 while in Idle
mode, the user should always set up a timer that will periodically exit Idle, service the WDT, and re-enter Idle mode.
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14.4. Register
WDTPRG (S:A7h)
WatchDog Timer Duration Programming register
7
6
5
4
3
2
1
0
-
-
-
-
-
S2
S1
S0
Bit Number Bit Mnemonic
Description
7
-
Reserved
The value read from this bit is indeterminate. Do not set this bit.
6
-
Reserved
The value read from this bit is indeterminate. Do not set this bit.
5
-
Reserved
The value read from this bit is indeterminate. Do not set this bit.
4
-
Reserved
The value read from this bit is indeterminate. Do not set this bit.
3
-
Reserved
The value read from this bit is indeterminate. Do not set this bit.
2
S2
WatchDog Timer Duration selection bit 2
Work in conjunction with bit 1 and bit 0.
1
S1
WatchDog Timer Duration selection bit 1
Work in conjunction with bit 2 and bit 0.
0
S0
WatchDog Timer Duration selection bit 0
Work in conjunction with bit 1 and bit 2.
Reset Value = XXXX X000b
Figure 62. WDTPRG Register
WDTRST (S:A6h Write only)
WatchDog Timer Enable register
7
6
5
4
3
2
1
0
-
-
-
-
-
-
-
-
Bit Number Bit Mnemonic
7
-
Description
Watchdog Control Value
Reset Value = 1111 1111b
NOTE:
The WDRST register is used to reset/enable the WDT by writing 1EH then E1H in sequence.
.
Figure 63. WDTRST Register
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15. Programmable Counter Array PCA
15.1. Introduction
The PCA provides more timing capabilities with less CPU intervention than the standard timer/counters. Its
advantages include reduced software overhead and improved accuracy. The PCA consists of a dedicated timer/
counter which serves as the time base for an array of five compare/capture modules. Its clock input can be
programmed to count any of the following signals:
•
•
•
•
PCA clock frequency / 6
PCA clock frequency / 2
Timer 0 overflow
External input on ECI (P1.2)
Each compare/capture modules can be programmed in any one of the following modes:
•
•
•
•
rising and/or trailing edge capture,
software timer,
high-speed output,
pulse width modulator.
Module 4 can also be programmed as a watchdog timer. see Section "PCA Watchdog Timer".
When the compare/capture modules are programmed in capture mode, software timer, or high speed output mode,
an interrupt can be generated when the module executes its function. All five modules plus the PCA timer overflow
share one interrupt vector.
The PCA timer/counter and compare/capture modules share Port 1 for external I/Os. These pins are listed below.
If the port is not used for the PCA, it can still be used for standard I/O.
PCA component
External I/O Pin
16-bit Counter
P1.2 / ECI
16-bit Module 0
P1.3 / CEX0
16-bit Module 1
P1.4 / CEX1
16-bit Module 2
P1.5 / CEX2
16-bit Module 3
P1.6 / CEX3
16-bit Module 4
P1.7 / CEX4
The PCA timer is a common time base for all five modules (see Figure 9). The timer count source is determined
from the CPS1 and CPS0 bits in the CMOD SFR (see Table 8) and can be programmed to run at:
•
•
•
•
1/6 the PCA clock frequency.
1/2 the PCA clock frequency.
the Timer 0 overflow.
the input on the ECI pin (P1.2).
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To PCA
modules
FPca/6
overflow
FPca / 2
CH
T0 OVF
It
CL
16 bit up/down counter
P1.2
CIDL
WDTE
CF
CR
CPS1
CPS0
ECF
CMOD
0xD9
CCF2
CCF1
CCF0
CCON
0xD8
Idle
CCF4
CCF3
Figure 64. PCA Timer/Counter
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15.2. PCA Interrupt
CF
CR
CCF4
CCF3
CCF2
CCF1
CCF0
CCON
0xD8
PCA Timer/Counter
Module 0
Module 1
To Interrupt
Module 2
Module 3
Module 4
CMOD.0
ECF
ECCFn CCAPMn.0
EC
EA
Figure 65. PCA Timer Interrupts
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15.3. PCA Capture Mode
To use one of the PCA modules in capture mode either one or both of the CCAPM bits CAPN and CAPP for
that module must be set. The external CEX input for the module (on port 1) is sampled for a transition. When a
valid transition occurs the PCA hardware loads the value of the PCA counter registers (CH and CL) into the
module’s capture registers (CCAPnL and CCAPnH). If the CCFn bit for the module in the CCON SFR and the
ECCFn bit in the CCAPMn SFR are set then an interrupt will be generated.
PCA Counter
CH
(8bits)
CL
(8bits)
CEXn
n = 0, 4
CCAPnH CCAPnL
PCA
Interrupt
Request
CCFn
CCON Reg
-
0CAPPnCAPNn000 ECCFn
0
7
CCAPMn Register (n = 0, 4)
Figure 66. PCA Capture Mode
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15.4. 16-bit Software Timer Mode
The PCA modules can be used as software timers by setting both the ECOM and MAT bits in the modules
CCAPMn register. The PCA timer will be compared to the module’s capture registers and when a match occurs
an interrupt will occur if the CCFn (CCON SFR) and the ECCFn (CCAPMn SFR) bits for the module are both set.
PCA Counter
CH
CL
Compare/Capture Module
CCAPnH CCAPnL
16-Bit
Comparator
Match
Enable
Toggle
CCFn
CCON reg
7
“0”
Reset
Write to
“1”
CCAPnL
Write to CCAPnH
CEXn
PCA
Interrupt
Request
ECOMn00MATnTOGn0ECCFn
0
CCAPMn Register
(n = 0, 4)
For software Timer mode, set ECOMn and MATn.
For high speed output mode, set ECOMn, MATn and
TOGn.
Figure 67. PCA 16-bit Software Timer and High Speed Output Mode
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15.5. High Speed Output Mode
In this mode the CEX output (on port 1) associated with the PCA module will toggle each time a match occurs
between the PCA counter and the module’s capture registers. To activate this mode the TOG, MAT, and ECOM
bits in the module’s CCAPMn SFR must be set.
CF
Write to
CCAPnH
CR
CCF4
CCF3
CCF2
CCF1
CCF0
CCON
0xD8
Reset
PCA IT
Write to
CCAPnL
“0”
CCAPnH
“1”
CCAPnL
Enable
16 bit comparator
CH
Match
CL
CEXn
PCA counter/timer
ECOMn CAPPn CAPNn MATn TOGn PWMn ECCFn
CCAPMn, n = 0 to 4
0xDA to 0xDE
Figure 68. PCA High speed Output Mode
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15.6. Pulse Width Modulator Mode
All the PCA modules can be used as PWM outputs. The output frequency depends on the source for the PCA
timer. All the modules will have the same output frequency because they all share the PCA timer. The duty cycle
of each module is independently variable using the module’s capture register CCAPLn. When the value of the
PCA CL SFR is less than the value in the module’s CCAPLn SFR the output will be low, when it is equal to or
greater than it, the output will be high. When CL overflows from FF to 00, CCAPLn is reloaded with the value
in CCAPHn. the allows the PWM to be updated without glitches. The PWM and ECOM bits in the module’s
CCAPMn register must be set to enable the PWM mode.
CCAPn
CL rolls over from FFh TO 00h
loads CCAPnH contents into
CCAPnL
CCAPxL
“0
CL < CCAPnL
8-Bit
Comparator
CL (8 bits)
CEX
CL >= CCAPnL
“1”
7
ECOMn0 00
0
0PWMn0
CCAPMn Register
Figure 69. PCA PWM Mode
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15.7. PCA Watchdog Timer
An on-board watchdog timer is available with the PCA to improve system reliability without increasing chip
count. Watchdog timers are useful for systems that are sensitive to noise, power glitches, or electrostatic
discharge. Module 4 is the only PCA module that can be programmed as a watchdog. However, this module
can still be used for other modes if the watchdog is not needed. The user pre-loads a 16-bit value in the
compare registers. Just like the other compare modes, this 16-bit value is compared to the PCA timer value.
If a match is allowed to occur, an internal reset will be generated. This will not cause the RST pin to be
driven high.
To hold off the reset, the user has three options:
• 1. periodically change the compare value so it will never match the PCA timer,
• 2. periodically change the PCA timer value so it will never match the compare values, or
• 3. disable the watchdog by clearing the WDTE bit before a match occurs and then re-enable it.
The first two options are more reliable because the watchdog timer is never disabled as in option #3. If the
program counter ever goes astray, a match will eventually occur and cause an internal reset. If other PCA
modules are being used the second option not recommended either. Remember, the PCA timer is the time
base for all modules; changing the time base for other modules would not be a good idea. Thus, in most
applications the first solution is the best option.
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15.8. PCA Registers
CMOD (S:D8h)
PCA Counter Mode Register
7
6
5
4
3
2
1
0
CIDL
WDTE
-
-
-
CPS1
CPS0
ECF
Bit Number Bit Mnemonic
Description
7
CIDL
PCA Counter Idle Control bit
Clear to let the PCA run during Idle mode.
Set to stop the PCA when Idle mode is invoked.
6
WDTE
Watchdog Timer Enable
Clear to disable Watchdog Timer function on PCA Module 4,
Set to enable it.
5
-
Reserved
The value read from this bit is indeterminate. Do not set this bit.
4
-
Reserved
The value read from this bit is indeterminate. Do not set this bit.
3
-
Reserved
The value read from this bit is indeterminate. Do not set this bit.
2
CPS1
1
CPS0
0
ECF
EWC Count Pulse
CPS1 CPS0
0
0
0
1
1
0
1
1
Select bits
Clock source
Internal Clock, FPca/6
Internal Clock, FPca/2
Timer 0 overflow
External clock at ECI/P1.2 pin (Max. Rate = FPca/4)
Enable PCA Counter Overflow Interrupt bit
Clear to disable CF bit in CCON register to generate an interrupt.
Set to enable CF bit in CCON register to generate an interrupt.
Reset Value = 00XX X000b
Figure 70. CMOD Register
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CCON (S:D8h)
PCA Counter Control Register
7
6
5
4
3
2
1
0
CF
CR
-
CCF4
CCF3
CCF2
CCF1
CCF0
Bit Number Bit Mnemonic
Description
7
CF
PCA Timer/Counter Overflow flag
Set by hardware when the PCA Timer/Counter rolls over. This generates a PCA interrupt request if
the ECF bit in CMOD register is set.
Must be cleared by software.
6
CR
PCA Timer/Counter Run Control bit
Clear to turn the PCA Timer/Counter off.
Set to turn the PCA Timer/Counter on.
5
-
4
3
2
1
0
Reserved
The value read from this bit is indeterminate. Do not set this bit.
CCF4
PCA Module 4 Compare/Capture flag
Set by hardware when a match or capture occurs. This generates a PCA interrupt request if the ECCF
4 bit in CCAPM 4 register is set.
Must be cleared by software.
CCF3
PCA Module 3 Compare/Capture flag
Set by hardware when a match or capture occurs. This generates a PCA interrupt request if the ECCF
3 bit in CCAPM 3 register is set.
Must be cleared by software.
CCF2
PCA Module 2 Compare/Capture flag
Set by hardware when a match or capture occurs. This generates a PCA interrupt request if the ECCF
2 bit in CCAPM 2 register is set.
Must be cleared by software.
CCF1
PCA Module 1 Compare/Capture flag
Set by hardware when a match or capture occurs. This generates a PCA interrupt request if the ECCF
1 bit in CCAPM 1 register is set.
Must be cleared by software.
CCF0
PCA Module 0 Compare/Capture flag
Set by hardware when a match or capture occurs. This generates a PCA interrupt request if the ECCF
0 bit in CCAPM 0 register is set.
Must be cleared by software.
Reset Value = 00X0 0000b
Figure 71. CCON Register
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CCAP0H (S:FAh)
CCAP1H (S:FBh )
CCAP2H (S:FCh)
CCAP3H (S:FDh)
CCAP4H (S:FEh)
PCA High Byte Compare/Capture Module n Register (n=0..4)
7
6
5
4
3
2
1
0
CCAPnH 7
CCAPnH 6
CCAPnH 5
CCAPnH 4
CCAPnH 3
CCAPnH 2
CCAPnH 1
CCAPnH 0
Bit Number Bit Mnemonic
7:0
CCAPnH 7:0
Description
High byte of EWC-PCA comparison or capture values
Reset Value = 0000 0000b
Figure 72. CCAPnH Registers
CCAP0L (S: EAh)
CCAP1L (S:EBh )
CCAP2L (S:ECh)
CCAP3L (S:EDh)
CCAP4L (S:EEh)
PCA Low Byte Compare/Capture Module n Register (n=0..4)
7
6
5
4
3
2
1
0
CCAPnL 7
CCAPnL 6
CCAPnL 5
CCAPnL 4
CCAPnL 3
CCAPnL 2
CCAPnL 1
CCAPnL 0
Bit Number Bit Mnemonic
7:0
CCAPnL 7:0
Description
Low byte of EWC-PCA comparison or capture values
Reset Value = 0000 0000b
Figure 73. CCAPnL Registers
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CCAPM0 (S:DAh)
CCAPM1 (S:DBh)
CCAPM2 (S:DCh)
CCAPM3 (S:DDh)
CCAPM4 (S:DEh)
PCA Compare/Capture Module n Mode registers (n=0..4)
7
6
5
4
3
2
1
0
-
ECOMn
CAPPn
CAPNn
MATn
TOGn
PWMn
ECCFn
Bit Number Bit Mnemonic
7
-
Description
Reserved
The Value read from this bit is indeterminate. Do not set this bit.
6
ECOMn
Enable Compare Mode Module x bit
Clear to disable the Compare function.
Set to enable the Compare function.
The Compare function is used to implement the software Timer, the high-speed output, the Pulse
Width Modulator (PWM) and the Watchdog Timer (WDT).
5
CAPPn
Capture Mode (Positive) Module x bit
Clear to disable the Capture function triggered by a positive edge on CEXx pin.
Set to enable the Capture function triggered by a positive edge on CEXx pin
4
CAPNn
Capture Mode (Negative) Module x bit
Clear to disable the Capture function triggered by a negative edge on CEXx pin.
Set to enable the Capture function triggered by a negative edge on CEXx pin.
MATn
Match Module x bit
Set when a match of the PCA Counter with the Compare/Capture register sets CCFx bit in CCON
register, flagging an interrupt.
Must be cleared by software.
2
TOGn
Toggle Module x bit
The toggle mode is configured by setting ECOMx, MATx and TOGx bits.
Set when a match of the PCA Counter with the Compare/Capture register toggles the CEXx pin.
Must be cleared by software.
1
PWMn
Pulse Width Modulation Module x Mode bit
Set to configure the module x as an 8-bit Pulse Width Modulator with output waveform on CEXx pin.
Must be cleared by software.
0
ECCFn
Enable CCFx Interrupt bit
Clear to disable CCFx bit in CCON register to generate an interrupt request.
Set to enable CCFx bit in CCON register to generate an interrupt request.
3
Reset Value = X000 0000b
Figure 74. CCAPMn Registers
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CH (S:F9h)
PCA Counter Register High value
7
6
5
4
3
2
1
0
CH 7
CH 6
CH 5
CH 4
CH 3
CH 2
CH 1
CH 0
Bit Number Bit Mnemonic
7:0
CH 7:0
Description
High byte of Timer/Counter
Reset Value = 0000 00000b
Figure 75. CH Register
CL (S:E9h)
PCA counter Register Low value
7
6
5
4
3
2
1
0
CL 7
CL 6
CL 5
CL 4
CL 3
CL 2
CL 1
CL 0
Bit Number Bit Mnemonic
7:0
CL0 7:0
Description
Low byte of Timer/Counter
Reset Value = 0000 00000b
Figure 76. CL Register
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16. Analog-to-Digital Converter (ADC)
16.1. Introduction
This section describes the on-chip 10 bit analog-to-digital converter of the T89C51AC2. Eight ADC channels are
available for sampling of the external sources AN0 to AN7. An analog multiplexer allows the single ADC converter
to select one from the 8 ADC channels as ADC input voltage (ADCIN). ADCIN is converted by the 10 bitcascaded potentiometric ADC.
Two kind of conversion are available:
- Standard conversion (8 bits).
- Precision conversion (10 bits).
For the precision conversion, set bit PSIDLE in ADCON register and start conversion. The chip is in a pseudoidle mode, the CPU doesn’t run but the peripherals are always running. This mode allows digital noise to be as
low as possible, to ensure high precision conversion.
For this mode it is necessary to work with end of conversion interrupt, which is the only way to wake up the chip.
If another interrupt occurs during the precision conversion, it will be treated only after this conversion is ended.
16.2. Features
• 8 channels with multiplexed inputs
• 10-bit cascaded potentiometric ADC
• Conversion time 20 micro-seconds
• Zero Error (offset) +/- 2 LSB max
• Positive Reference Voltage Range 2.4 to 3.0Volt
• ADCIN Range 0 to 3Volt
• Integral non-linearity typical 1 LSB, max. 2 LSB
• Differential non-linearity typical 0.5 LSB, max. 1 LSB
• Conversion Complete Flag or Conversion Complete Interrupt
• Selected ADC Clock
16.3. ADC Port1 I/O Functions
Port 1 pins are general I/O that are shared with the ADC channels. The channel select bit in ADCF register define
which ADC channel/port1 pin will be used as ADCIN. The remaining ADC channels/port1 pins can be used as
general purpose I/O or as the alternate function that is available. Writes to the port register which aren’t selected
by the ADCF will not have any effect.
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ADCON.5
ADCON.3
ADEN
ADSST
ADC
Interrupt
Request
ADCON.4
ADEOC
ADC
CLOCK
CONTROL
EADC
AN0/P1.0
000
AN1/P1.1
001
AN2/P1.2
010
AN3/P1.3
011
AN4/P1.4
100
AN5/P1.5
101
AN6/P1.6
110
AN7/P1.7
111
IEN1.1
ADCIN
8
ADDH
2
ADDL
+
SAR
-
AVSS
Sample and Hold
10
R/2R DAC
SCH2
SCH1
SCH0
ADCON.2
ADCON.1
ADCON.0
VAREF VAGND
Figure 77. ADC Description
Figure 78 shows the timing diagram of a complete conversion. For simplicity, the figure depicts the waveforms in
idealized form and do not provide precise timing information. For ADC characteristics and timing parameters refer
to the Section “AC Characteristics” of the T89C51AC2 datasheet.
CLK
ADEN
TSETUP
ADSST
TCONV
ADEOC
Figure 78. Timing Diagram
NOTE:
Tsetup = 4 us
Tconv=11 clock ADC
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16.4. ADC Converter Operation
A start of single A/D conversion is triggered by setting bit ADSST (ADCON.3).
The busy flag ADSST(ADCON.3) is automatically set when an A/D conversion is running. After completion of
the A/D conversion, it is cleared by hardware. This flag can be read only, a write has no effect.
The end-of-conversion flag ADEOC (ADCON.4) is set when the value of conversion is available in ADDH and
ADDL, it is cleared by software. If the bit EADC (IEN1.1) is set, an interrupt occur when flag ADEOC is set
(see Figure 80). Clear this flag for re-arming the interrupt.
The bits SCH0 to SCH2 in ADCON register are used for the analog input channel selection.
Before Starting Power reduction modes the ADC conversion has to be completed.
Table 21. Selected Analog input
SCH2
SCH1
SCH0
Selected Analog input
0
0
0
AN0
0
0
1
AN1
0
1
0
AN2
0
1
1
AN3
1
0
0
AN4
1
0
1
AN5
1
1
0
AN6
1
1
1
AN7
16.5. Voltage Conversion
When the ADCIN is equals to VAREF the ADC converts the signal to 3FFh (full scale). If the input voltage
equals VAGND, the ADC converts it to 000h. Input voltage between VAREF and VAGND are a straight-line
linear conversion. All other voltages will result in 3FFh if greater than VAREF and 000h if less than VAGND.
Note that ADCIN should not exceed VAREF absolute maximum range!
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16.6. Clock Selection
The maximum clock frequency for ADC is 700KHz. A prescaler is featured (ADCCLK) to generate the ADC
clock from the oscillator frequency.
conversion clock fADC
CPU
CLOCK
÷2
Prescaler ADCLK
CPU Core Clock Symbol
A/D
Converter
Figure 79. A/D Converter clock
16.7. ADC Standby Mode
When the ADC is not used, it is possible to set it in standby mode by clearing bit ADEN in ADCON register.
In this mode the power dissipation is about 1uW.
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16.8. IT ADC management
An interrupt end-of-conversion will occurs when the bit ADEOC is actived and the bit EADC is set. For re-arming
the interrupt the bit ADEOC must be cleared by software.
ADCI
ADEOC
ADCON.2
EADC
IEN1.1
Figure 80. ADC interrupt structure
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16.9. Registers
ADCF (S:F6h)
ADC Configuration
7
6
5
4
3
2
1
0
CH 7
CH 6
CH 5
CH 4
CH 3
CH 2
CH 1
CH 0
Bit Number
Bit
Mnemonic
7-0
CH 0:7
Description
Channel Configuration
Set to use P1.x as ADC input.
Clear tu use P1.x as standart I/O port.
Reset Value=0000 0000b
Figure 81. ADCF Register
ADCON (S:F3h)
ADC Control Register
7
6
5
4
3
2
1
0
-
PSIDLE
ADEN
ADEOC
ADSST
SCH2
SCH1
SCH0
Bit Number Bit Mnemonic
Description
7
-
6
PSIDLE
5
ADEN
4
ADEOC
End Of Conversion
Set by hardware when ADC result is ready to be read. This flag can generate an interrupt.
Must be cleared by software.
3
ADSST
Start and Status
Set to start an A/D conversion.
Cleared by hardware after completion of the conversion
2-0
SCH2:0
Selection of channel to convert
see Table 21
Pseudo Idle mode (best precision)
Set to put in idle mode during conversion
Clear to converte without idle mode.
Enable/Standby Mode
Set to enable ADC
Clear for Standby mode (power dissipation 1 uW).
Reset Value=X000 0000b
Figure 82. ADCON Register
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ADCLK (S:F2h)
ADC Clock Prescaler
7
6
5
4
3
2
1
0
-
-
-
PRS 4
PRS 3
PRS 2
PRS 1
PRS 0
Bit Number Bit Mnemonic
7-5
-
4-0
PRS4:0
Description
Reserved
The value read from these bits are indeterminate. Do not set these bits.
Clock Prescaler
fADC = fosc / (4 (or 2 in X2 mode)* PRS)
Reset Value: XXX0 0000b
Figure 83. ADCLK Register
ADDH (S:F5h Read Only)
ADC Data High byte register
7
6
5
4
3
2
1
0
ADAT 9
ADAT 8
ADAT 7
ADAT 6
ADAT 5
ADAT 4
ADAT 3
ADAT 2
Bit Number Bit Mnemonic
7-0
ADAT9:2
Description
ADC result
bits 9-2
Reset Value: 00h
Figure 84. ADDH Register
ADDL (S:F4h Read Only)
ADC Data Low byte register
7
6
5
4
3
2
1
0
-
-
-
-
-
-
ADAT 1
ADAT 0
Bit Number Bit Mnemonic
7-2
-
1-0
ADAT1:0
Description
Reserved
The value read from these bits are indeterminate. Do not set these bits.
ADC result
bits 1-0
Reset Value: 00h
Figure 85. ADDL Register
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17. Interrupt System
17.1. Introduction
The CAN Controller has a total of 8 interrupt vectors: two external interrupts (INT0 and INT1), three timer
interrupts (timers 0, 1 and 2), a serial port interrupt, a PCA and an ADC. These interrupts are shown below.
INT0#
00
01
10
11
External
Interrupt 0
Highest
Priority
Interrupts
EX0
00
01
10
11
IEN0.0
Timer 0
ET0
00
01
10
11
IEN0.1
INT1#
External
Interrupt 1
EX1
00
01
10
11
IEN0.2
Timer 1
ET1
CEX0:5
00
01
10
11
IEN0.3
PCA
EC
TxD
00
01
10
11
IEN0.6
UART
RxD
ES
IEN0.4
00
01
10
11
Timer 2
ET2
IEN0.5
AIN1:0
00
01
10
11
A to D
Converter
EADC
IEN1.1
EA
IPH/L
IEN0.7
Interrupt Enable
Priority Enable
Lowest Priority Interrupts
Figure 86. Interrupt Control System
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Each of the interrupt sources can be individually enabled or disabled by setting or clearing a bit in the Interrupt
Enable register. This register also contains a global disable bit which must be cleared to disable all the interrupts
at the same time.
Each interrupt source can also be individually programmed to one of four priority levels by setting or clearing a
bit in the Interrupt Priority registers. The Table below shows the bit values and priority levels associated with each
combination.
Table 22. Priority Level Bit Values
IPH.x
IPL.x
Interrupt Level Priority
0
0
0 (Lowest)
0
1
1
1
0
2
1
1
3 (Highest)
A low-priority interrupt can be interrupted by a high priority interrupt but not by another low-priority interrupt. A
high-priority interrupt cannot be interrupted by any other interrupt source.
If two interrupt requests of different priority levels are received simultaneously, the request of the higher priority
level is serviced. If interrupt requests of the same priority level are received simultaneously, an internal polling
sequence determines which request is serviced. Thus within each priority level there is a second priority structure
determined by the polling sequence, see Table 23.
Table 23. Interrupt priority Within level
Interrupt Name
Interrupt Address Vector
Priority Number
external interrupt (INT0)
0003h
1
Timer0 (TF0)
000Bh
2
external interrupt (INT1)
0013h
3
Timer1 (TF1)
001Bh
4
PCA (CF or CCFn)
0033h
5
UART (RI or TI)
0023h
6
Timer2 (TF2)
002Bh
7
-
-
-
ADC (ADCI)
0043h
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17.2. Registers
IEN0 (S:A8h)
Interrupt Enable Register
7
6
5
4
3
2
1
0
EA
EC
ET2
ES
ET1
EX1
ET0
EX0
Bit Number Bit Mnemonic
Description
7
EA
Enable All interrupt bit
Clear to disable all interrupts.
Set to enable all interrupts.
If EA=1, each interrupt source is individually enabled or disabled by setting or clearing its interrupt
enable bit.
6
EC
PCA Interrupt Enable
Clear to disable the PCA interrupt.
Set to enable the PCA interrupt.
5
ET2
Timer 2 overflow interrupt Enable bit
Clear to disable timer 2 overflow interrupt.
Set to enable timer 2 overflow interrupt.
4
ES
Serial port Enable bit
Clear to disable serial port interrupt.
Set to enable serial port interrupt.
3
ET1
Timer 1 overflow interrupt Enable bit
Clear to disable timer 1 overflow interrupt.
Set to enable timer 1 overflow interrupt.
2
EX1
External interrupt 1 Enable bit
Clear to disable external interrupt 1.
Set to enable external interrupt 1.
1
ET0
Timer 0 overflow interrupt Enable bit
Clear to disable timer 0 overflow interrupt.
Set to enable timer 0 overflow interrupt.
0
EX0
External interrupt 0 Enable bit
Clear to disable external interrupt 0.
Set to enable external interrupt 0.
Reset Value: 0000 0000b
bit addressable
Figure 87. IEN0 Register
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IEN1 (S:E8h)
Interrupt Enable Register
7
6
5
4
-
-
-
-
Bit Number Bit Mnemonic
3
2
1
0
-
EADC
-
Description
7
-
Reserved
The value read from this bit is indeterminate. Do not set this bit.
6
-
Reserved
The value read from this bit is indeterminate. Do not set this bit.
5
-
Reserved
The value read from this bit is indeterminate. Do not set this bit.
4
-
Reserved
The value read from this bit is indeterminate. Do not set this bit.
3
-
Reserved
The value read from this bit is indeterminate. Do not set this bit.
2
-
Reserved
The value read from this bit is indeterminate. Do not set this bit.
1
EADC
0
-
ADC Interrupt Enable bit
Clear to disable the ADC interrupt.
Set to enable the ADC interrupt.
Reserved
The value read from this bit is indeterminate. Do not set this bit.
Reset Value: xxxx xx0xb
bit addressable
Figure 88. IEN1 Register
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IPL0 (S:B8h)
Interrupt Enable Register
7
6
5
4
3
2
1
0
-
PPC
PT2
PS
PT1
PX1
PT0
PX0
Bit Number Bit Mnemonic
Description
Reserved
The value read from this bit is indeterminate. Do not set this bit.
7
-
6
PPC
EWC Counter Interrupt Priority bit
Refer to PPCH for priority level
5
PT2
Timer 2 overflow interrupt Priority bit
Refer to PT2H for priority level.
4
PS
Serial port Priority bit
Refer to PSH for priority level.
3
PT1
Timer 1 overflow interrupt Priority bit
Refer to PT1H for priority level.
2
PX1
External interrupt 1 Priority bit
Refer to PX1H for priority level.
1
PT0
Timer 0 overflow interrupt Priority bit
Refer to PT0H for priority level.
0
PX0
External interrupt 0 Priority bit
Refer to PX0H for priority level.
Reset Value: x000 0000b
bit addressable
Figure 89. IPL0 Register
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IPL1 (S:F8h)
Interrupt Priority Low Register 1
7
6
5
4
3
2
1
0
-
-
-
-
-
-
PADCL
-
Bit Number Bit Mnemonic
Description
7
-
Reserved
The value read from this bit is indeterminate. Do not set this bit.
6
-
Reserved
The value read from this bit is indeterminate. Do not set this bit.
5
-
Reserved
The value read from this bit is indeterminate. Do not set this bit.
4
-
Reserved
The value read from this bit is indeterminate. Do not set this bit.
3
-
Reserved
The value read from this bit is indeterminate. Do not set this bit.
2
-
Reserved
The value read from this bit is indeterminate. Do not set this bit.
1
PADCL
0
-
ADC Interrupt Priority level less significant bit.
Refer to PSPIH for priority level.
Reserved
The value read from this bit is indeterminate. Do not set this bit.
Reset Value: xxxx xx0xb
bit addressable
Figure 90. IPL1 Register
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IPH0 (B7h)
Interrupt High Priority Register
7
6
5
4
3
2
1
0
-
PPCH
PT2H
PSH
PT1H
PX1H
PT0H
PX0H
Bit Number Bit Mnemonic
7
6
5
4
3
2
1
0
-
Description
Reserved
The value read from this bit is indeterminate. Do not set this bit.
PPCH
EWC-PCA Counter Interrupt Priority level most significant bit
PPCH PPC
Priority level
0
0
Lowest
0
1
1
0
1
1
Highest priority
PT2H
Timer 2 overflow interrupt High Priority bit
PT2H PT2
Priority Level
0
0
Lowest
0
1
1
0
1
1
Highest
PSH
Serial port High Priority bit
PSH
PS
Priority Level
0
0
Lowest
0
1
1
0
1
1
Highest
PT1H
Timer 1 overflow interrupt High Priority bit
PT1H PT1
Priority Level
0
0
Lowest
0
1
1
0
1
1
Highest
PX1H
External interrupt 1
PX1H
0
0
1
1
PT0H
Timer 0 overflow interrupt High Priority bit
PT0H PT0
Priority Level
0
0
Lowest
0
1
1
0
1
1
Highest
PX0H
External interrupt 0
PX0H
0
0
1
1
High Priority bit
PX1
Priority Level
0
Lowest
1
0
1
Highest
high priority bit
PX0
Priority Level
0
Lowest
1
0
1
Highest
Reset Value: X000 0000b
Figure 91. IPL0 Register
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IPH1 (S:FFh)
Interrupt high priority Register 1
7
6
5
4
3
2
1
0
-
-
-
-
-
-
PADCH
-
Bit Number Bit Mnemonic
Description
7
-
Reserved
The value read from this bit is indeterminate. Do not set this bit.
6
-
Reserved
The value read from this bit is indeterminate. Do not set this bit.
5
-
Reserved
The value read from this bit is indeterminate. Do not set this bit.
4
-
Reserved
The value read from this bit is indeterminate. Do not set this bit.
3
-
Reserved
The value read from this bit is indeterminate. Do not set this bit.
2
-
Reserved
The value read from this bit is indeterminate. Do not set this bit.
1
PADCH
0
-
ADC Interrupt Priority level most significant bit
PADCH PADCL
Priority level
0
0
Lowest
0
1
1
0
1
1
Highest
Reserved
The value read from this bit is indeterminate. Do not set this bit.
Reset Value = xxxx xx0xb
Figure 92. IPH1 Register
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18. Electrical Characteristics
18.1. Absolute Maximum Ratings (1)
Ambiant Temperature Under Bias:
I = industrial -40°C to 85°C
Storage Temperature -65°C to + 150°C
Voltage on VCC to VSS-0.5 V to + 6V
Voltage on Any Pin to VSS-0.5 V to VCC + 0.2 V
Power Dissipation 1 W(2)
NOTES
1. Stresses at or above those listed under “ Absolute Maximum Ratings” may cause permanent damage to the device. This is a stress rating only
and functional operation of the device at these or any other conditions above those indicated in the operational sections of this specification is not
implied. Exposure to absolute maximum rating conditions may affect device reliability.
2. This value is based on the maximum allowable die temperature and the thermal resistance of the package.
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18.2. DC Parameters for Standard Voltage
TA = -40°C to +85°C; VSS = 0 V; VCC = 5 V ± 10%; F = 0 to 40 MHz.
Symbol
Parameter
Min
VIL
Input Low Voltage
VIH
Input High Voltage except XTAL1, RST
VIH1
Input High Voltage, XTAL1, RST
VOL
Output Low Voltage, ports 1, 2, 3 and 4(6)
VOL1
VOH
Typ
Max
Unit
-0.5
0.7(7)
V
0.2 VCC + 0.9
VCC + 0.5
V
0.7 VCC
VCC + 0.5
V
0.3
0.45
1.0
V
V
V
IOL = 100 µA(4)
0.3
0.45
1.0
V
V
V
IOL = 200 µA(4)
V
V
V
IOH = -10 µA
Output Low Voltage, port 0, ALE, PSEN (6)
Output High Voltage, ports 1, 2, 3, 4 and 5
VCC - 0.3
VCC - 0.7
VCC - 1.5
VOH1
Output High Voltage, port 0, ALE, PSEN
VCC - 0.3
V
V
V
VCC - 1.5
RST Pulldown Resistor
20
IOL = 1.6 mA(4)
IOL = 3.5 mA(4)
IOL = 3.2 mA(4)
IOL = 7.0 mA(4)
IOH = -30 µA
IOH = -60 µA
VCC = 5 V ± 10%
VCC - 0.7
RRST
Test Conditions
IOH = -200 µA
IOH = -3.2 mA
IOH = -7.0 mA
VCC = 5 V ± 10%
40 (5)
200
kΩ
IIL
Logical 0 Input Current ports 1, 2, 3 and 4
-50
µA
Vin = 0.45 V
ILI
Input Leakage Current
±10
µA
0.45 V < Vin < VCC
ITL
Logical 1 to 0 Transition Current, ports 1, 2, 3
and 4
-650
µA
Vin = 2.0 V
CIO
Capacitance of I/O Buffer
10
pF
Fc = 1 MHz
TA = 25°C
IPD
Power Down Current
350
µA
4.5 V < VCC < 5.5 V(3)
ICC
Power Supply Current (Typical)
ICCOP = 0.5 Freq (MHz) + 3 mA
120
ICCIDLE = 0.3 Freq (MHz) + 2 mA
Table 24. DC Parameters in Standard Voltage
NOTES
1. Operating ICC is measured with all output pins disconnected; XTAL1 driven with TCLCH, TCHCL = 5 ns (see Figure 96.), VIL = VSS + 0.5 V,
VIH = VCC - 0.5V; XTAL2 N.C.; EA = RST = Port 0 = VCC. ICC would be slightly higher if a crystal oscillator used (see Figure 93.).
2. Idle ICC is measured with all output pins disconnected; XTAL1 driven with TCLCH, TCHCL = 5 ns, VIL = VSS + 0.5 V, VIH = VCC - 0.5 V; XTAL2
N.C; Port 0 = VCC; EA = RST = VSS (see Figure 94.).
3. Power Down ICC is measured with all output pins disconnected; EA = VSS, PORT 0 = VCC; XTAL2 NC.; RST = VSS (see Figure 95.). In addition,
the WDT must be inactive and the POF flag must be set.
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4. Capacitance loading on Ports 0 and 2 may cause spurious noise pulses to be superimposed on the VOLs of ALE and Ports 1 and 3. The noise is
due to external bus capacitance discharging into the Port 0 and Port 2 pins when these pins make 1 to 0 transitions during bus operation. In the worst
cases (capacitive loading 100pF), the noise pulse on the ALE line may exceed 0.45V with maxi VOL peak 0.6V. A Schmitt Trigger use is not necessary.
5. Typicals are based on a limited number of samples and are not guaranteed. The values listed are at room temperature..
6. Under steady state (non-transient) conditions, IOL must be externally limited as follows:
Maximum IOL per port pin: 10 mA
Maximum IOL per 8-bit port:
Port 0: 26 mA
Ports 1, 2 and 3: 15 mA
Maximum total IOL for all output pins: 71 mA
If IOL exceeds the test condition, VOL may exceed the related specification. Pins are not guaranteed to sink current greater than the listed test conditions.
7. Lower than standart C51 product independant from Vcc supply.
VCC
ICC
VCC
P0
VCC
RST
(NC)
CLOCK
SIGNAL
VCC
EA
XTAL2
XTAL1
VSS
All other pins are disconnected.
Figure 93. ICC Test Condition, Active Mode
VCC
ICC
VCC
VCC
P0
RST
(NC)
CLOCK
SIGNAL
EA
XTAL2
XTAL1
VSS
All other pins are disconnected.
Figure 94. ICC Test Condition, Idle Mode
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VCC
ICC
VCC
VCC
P0
RST
(NC)
EA
XTAL2
XTAL1
VSS
All other pins are disconnected.
Figure 95. ICC Test Condition, Power-Down Mode
VCC-0.5V
0.45V
TCLCH
TCHCL
TCLCH = TCHCL = 5ns.
0.7VCC
0.2VCC-0.1
Figure 96. Clock Signal Waveform for ICC Tests in Active and Idle Modes
18.3. DC Parameters for A/D Converter
Table 25. DC Parameters for AD Converter
Symbol
Parameter
Min
AVin
Analog input voltage
Rref
Resistance between Vref and Vss
Reference voltage
Analog input Capacitance
Integral non linearity
Differential non linearity
Offset error
Vref
Cai
INL
DNL
OE
Typ
Vss- 0.2
12
2.40
Max
Unit
Vref + 0.2
V
18
60
1
0.5
-2
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24
3.00
2
1
2
Test Conditions
KOhm
V
pF During sampling
lsb
lsb
lsb
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18.4. AC Parameters
18.4.1. Explanation of the AC Symbols
Each timing symbol has 5 characters. The first character is always a “T” (stands for time). The other characters,
depending on their positions, stand for the name of a signal or the logical status of that signal. The following is
a list of all the characters and what they stand for.
Example:TAVLL = Time for Address Valid to ALE Low.
TLLPL = Time for ALE Low to PSEN Low.
TA = -40°C to +85°C; VSS = 0 V; VCC = 5 V ±10% ; F = 0 to 40 MHz.
TA = -40°C to +85°C; VSS = 0 V; VCC = 5 V ± 10%.
(Load Capacitance for port 0, ALE and PSEN = 60 pF; Load Capacitance for all other outputs = 60 pF.)
Table 26, Table 29 and Table 32 give the description of each AC symbols.
Table 27, Table 30 and Table 33 give for each range the AC parameter.
Table 28, Table 31 and Table 34 give the frequency derating formula of the AC parameter for each speed range
description. To calculate each AC symbols. take the x value and use this value in the formula.
Example: TLLIV and 20 MHz, Standard clock.
x = 30 ns
T = 50 ns
TCCIV = 4T - x = 170 ns
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18.4.2. External Program Memory Characteristics
Table 26. Symbol Description
Symbol
T
Parameter
Oscillator clock period
TLHLL
ALE pulse width
TAVLL
Address Valid to ALE
TLLAX
Address Hold After ALE
TLLIV
ALE to Valid Instruction In
TLLPL
ALE to PSEN
TPLPH
PSEN Pulse Width
TPLIV
PSEN to Valid Instruction In
TPXIX
Input Instruction Hold After PSEN
TPXIZ
Input Instruction FloatAfter PSEN
TAVIV
Address to Valid Instruction In
TPLAZ
PSEN Low to Address Float
Table 27. AC Parameters for a Fix Clock (F= 40 MHz)
Symbol
Units
Min
Max
T
25
ns
TLHLL
40
ns
TAVLL
10
ns
TLLAX
10
ns
TLLIV
70
ns
TLLPL
15
ns
TPLPH
55
ns
TPLIV
TPXIX
35
0
ns
ns
TPXIZ
18
ns
TAVIV
85
ns
TPLAZ
10
ns
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Table 28. AC Parameters for a Variable Clock
Symbol
Type
Standard
Clock
X2 Clock
X parameter
Units
TLHLL
Min
2T-x
T-x
10
ns
TAVLL
Min
T-x
0.5 T - x
15
ns
TLLAX
Min
T-x
0.5 T - x
15
ns
TLLIV
Max
4T-x
2T-x
30
ns
TLLPL
Min
T-x
0.5 T - x
10
ns
TPLPH
Min
3T-x
1.5 T - x
20
ns
TPLIV
Max
3T-x
1.5 T - x
40
ns
TPXIX
Min
x
x
0
ns
TPXIZ
Max
T-x
0.5 T - x
7
ns
TAVIV
Max
5T-x
2.5 T - x
40
ns
TPLAZ
Max
x
x
10
ns
18.4.3. External Program Memory Read Cycle
12 TCLCL
TLHLL
TLLIV
ALE
TLLPL
TPLPH
PSEN
TLLAX
TAVLL
PORT 0
INSTR IN
TPLIV
TPLAZ
A0-A7
TPXAV
TPXIZ
TPXIX
INSTR IN
A0-A7
INSTR IN
TAVIV
PORT 2
ADDRESS
OR SFR-P2
ADDRESS A8-A15
108
ADDRESS A8-A15
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18.4.4. External Data Memory Characteristics
Table 29. Symbol Description
Symbol
Parameter
TRLRH
RD Pulse Width
TWLWH
WR Pulse Width
TRLDV
RD to Valid Data In
TRHDX
Data Hold After RD
TRHDZ
Data Float After RD
TLLDV
ALE to Valid Data In
TAVDV
Address to Valid Data In
TLLWL
ALE to WR or RD
TAVWL
Address to WR or RD
TQVWX
Data Valid to WR Transition
TQVWH
Data set-up to WR High
TWHQX
Data Hold After WR
TRLAZ
RD Low to Address Float
TWHLH
RD or WR High to ALE high
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Table 30. AC Parameters for a Fix Clock (F= 40 MHz)
Symbol
Units
Min
Max
TRLRH
130
ns
TWLWH
130
ns
TRLDV
TRHDX
100
0
ns
ns
TRHDZ
30
ns
TLLDV
160
ns
TAVDV
165
ns
100
ns
TLLWL
50
TAVWL
75
ns
TQVWX
10
ns
TQVWH
160
ns
TWHQX
15
ns
TRLAZ
TWHLH
10
0
ns
40
ns
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Table 31. AC Parameters for a Variable Clock
Symbol
Type
Standard
Clock
X2 Clock
X parameter
Units
TRLRH
Min
6T-x
3T-x
20
ns
TWLWH
Min
6T-x
3T-x
20
ns
TRLDV
Max
5T-x
2.5 T - x
25
ns
TRHDX
Min
x
x
0
ns
TRHDZ
Max
2T-x
T-x
20
ns
TLLDV
Max
8T-x
4T -x
40
ns
TAVDV
Max
9T-x
4.5 T - x
60
ns
TLLWL
Min
3T-x
1.5 T - x
25
ns
TLLWL
Max
3T+x
1.5 T + x
25
ns
TAVWL
Min
4T-x
2T-x
25
ns
TQVWX
Min
T-x
0.5 T - x
15
ns
TQVWH
Min
7T-x
3.5 T - x
15
ns
TWHQX
Min
T-x
0.5 T - x
10
ns
TRLAZ
Max
x
x
0
ns
TWHLH
Min
T-x
0.5 T - x
15
ns
TWHLH
Max
T+x
0.5 T + x
15
ns
18.4.5. External Data Memory Write Cycle
TWHLH
ALE
PSEN
TLLWL
TWLWH
WR
TLLAX
PORT 0
TQVWX
TQVWH
A0-A7
TWHQX
DATA OUT
TAVWL
PORT 2
ADDRESS
OR SFR-P2
ADDRESS A8-A15 OR SFR P2
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18.4.6. External Data Memory Read Cycle
TWHLH
TLLDV
ALE
PSEN
TLLWL
TRLRH
RD
TRHDZ
TAVDV
TLLAX
PORT 0
DATA IN
TAVWL
PORT 2
TRHDX
A0-A7
ADDRESS
OR SFR-P2
TRLAZ
ADDRESS A8-A15 OR SFR P2
18.4.7. Serial Port Timing - Shift Register Mode
Table 32. Symbol Description (F= 40 MHz)
Symbol
Parameter
TXLXL
Serial port clock cycle time
TQVHX
Output data set-up to clock rising edge
TXHQX
Output data hold after clock rising edge
TXHDX
Input data hold after clock rising edge
TXHDV
Clock rising edge to input data valid
Table 33. AC Parameters for a Fix Clock (F= 40 MHz)
Units
Symbol
Min
Max
TXLXL
300
ns
TQVHX
200
ns
TXHQX
30
ns
TXHDX
0
ns
TXHDV
117
112
ns
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Table 34. AC Parameters for a Variable Clock
Units
Symbol
Type
Standard
Clock
X2 Clock
X parameter
for -M range
TXLXL
Min
12 T
6T
TQVHX
Min
10 T - x
5T-x
50
ns
TXHQX
Min
2T-x
T-x
20
ns
TXHDX
Min
x
x
0
ns
TXHDV
Max
10 T - x
5 T- x
133
ns
ns
18.4.8. Shift Register Timing Waveforms
0
INSTRUCTION
1
2
3
4
5
6
7
8
ALE
TXLXL
CLOCK
TXHQX
TQVXH
OUTPUT DATA
0
WRITE to SBUF
TXHDV
INPUT DATA
1
2
3
4
5
6
7
TXHDX
VALID
VALID
VALID
SET TI
VALID
VALID
VALID
VALID
VALID
SET RI
CLEAR RI
18.4.9. External Clock Drive Characteristics (XTAL1)
Symbol
Parameter
Min
Max
Units
TCLCL
Oscillator Period
25
ns
TCHCX
High Time
5
ns
TCLCX
Low Time
5
ns
TCLCH
Rise Time
5
ns
TCHCL
Fall Time
5
ns
60
%
TCHCX/TCLCX
Cyclic ratio in X2 mode
40
Table 35. AC Parameters
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18.4.10. External Clock Drive Waveforms
VCC-0.5V
0.45V
0.7VCC
0.2VCC-0.1
TCHCX
TCLCH
TCLCX
TCHCL
TCLCL
18.4.11. AC Testing Input/Output Waveforms
VCC -0.5 V
0.2 VCC + 0.9
INPUT/OUTPUT
0.2 VCC - 0.1
0.45 V
AC inputs during testing are driven at VCC - 0.5 for a logic “1” and 0.45V for a logic “0”. Timing measurement
are made at VIH min for a logic “1” and VIL max for a logic “0”.
18.4.12. Float Waveforms
FLOAT
VOH - 0.1 V
VOL + 0.1 V
VLOAD
VLOAD + 0.1 V
VLOAD - 0.1 V
For timing purposes as port pin is no longer floating when a 100 mV change from load voltage occurs and begins
to float when a 100 mV change from the loaded VOH/VOL level occurs. IOL/IOH ≥ ± 20mA.
18.4.13. Clock Waveforms
Valid in normal clock mode. In X2 mode XTAL2 must be changed to XTAL2/2.
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INTERNAL
CLOCK
STATE4
STATE5
STATE6
STATE1
STATE2
STATE3
STATE4
STATE5
P1
P1
P1
P1
P1
P1
P1
P1
P2
P2
P2
P2
P2
P2
P2
P2
XTAL2
ALE
THESE SIGNALS ARE NOT ACTIVATED DURING THE
EXECUTION OF A MOVX INSTRUCTION
EXTERNAL PROGRAM MEMORY FETCH
PSEN
P0
DATA
SAMPLED
FLOAT
P2 (EXT)
PCL OUT
DATA
SAMPLED
FLOAT
PCL OUT
DATA
SAMPLED
FLOAT
PCL OUT
INDICATES ADDRESS TRANSITIONS
READ CYCLE
RD
PCL OUT (IF PROGRAM
MEMORY IS EXTERNAL)
P0
DPL OR Rt OUT
DATA
SAMPLED
FLOAT
INDICATES DPH OR P2 SFR TO PCH TRANSITION
P2
WRITE CYCLE
WR
P0
PCL OUT (EVEN IF PROGRAM
MEMORY IS INTERNAL)
DPL OR Rt OUT
PCL OUT (IF PROGRAM
MEMORY IS EXTERNAL)
DATA OUT
P2
INDICATES DPH OR P2 SFR TO PCH TRANSITION
PORT OPERATION
MOV PORT SRC
OLD DATA NEW DATA
P0 PINS SAMPLED
P0 PINS SAMPLED
MOV DEST P0
MOV DEST PORT (P1. P2. P3)
(INCLUDES INTO. INT1. TO T1)
SERIAL PORT SHIFT CLOCK
P1, P2, P3 PINS SAMPLED
RXD SAMPLED
P1, P2, P3 PINS SAMPLED
RXD SAMPLED
TXD (MODE 0)
This diagram indicates when signals are clocked internally. The time it takes the signals to propagate to the pins,
however, ranges from 25 to 125 ns. This propagation delay is dependent on variables such as temperature and pin
loading. Propagation also varies from output to output and component. Typically though (TA=25°C fully loaded)
RD and WR propagation delays are approximately 50ns. The other signals are typically 85 ns. Propagation delays
are incorporated in the AC specifications.
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19. Ordering Information
T
-RL
89C51AC2
Packages:
RL: TQFP44
SL: PLCC44
M
C
S
Temperature Range
C:Commercial 0 to 70oC
I:Industrial -40 to 85oC
E:Enginering Sample
89C51AC2 ( 32 Kbytes Flash )
-M:
VCC: 5V
40 MHz, X1 mode
20 MHz, X2 mode
Conditioning
S: Stick
T: Tray
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Table 36. Possible order entries
Extension
-SLSCM
-SLSIM
-RLTCM
-RLTIM
-SLSEM
-RLTEM
Type
Stick, PLCC44, Com
Stick, PLCC44, Ind
Tray, TQFP44, Com
Tray, TQFP44, Ind
Stick, PLCC44, Sample
Tray, TQFP44, Sample
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