ST72T311J2T6 STMicroelectronics, ST72T311J2T6 Datasheet - Page 33

• Manufacturer Part Number: ST72T311J2T6
• Description: 8-bit Microcontrollers - MCU OTP EPROM 8K SPI/I2C
• Manufacturer: STMicroelectronics

Specifications of ST72T311J2T6

• Core: ST7
• Data Bus Width: 8 bit
• Maximum Clock Frequency: 8 MHz
• Program Memory Size: 8 KB
• Data Ram Size: 384 B
• On-chip Adc: Yes
• Operating Supply Voltage: 3 V to 5.5 V
• Package / Case: TQFP-44
• Mounting Style: SMD/SMT
• A/d Bit Size: 8 bit
• A/d Channels Available: 6
• Interface Type: SCI, SPI
• Maximum Operating Temperature: + 85 C
• Minimum Operating Temperature: - 40 C
• Number Of Programmable I/os: 44
• Number Of Timers: 2
• On-chip Dac: No
• Program Memory Type: OTP EPROM
• Factory Pack Quantity: 160
• Supply Voltage - Max: 5.5 V
• Supply Voltage - Min: 3 V

WATCHDOG TIMER (Cont’d)
The application program must write in the CR reg-
ister at regular intervals during normal operation to
prevent an MCU reset. The value to be stored in
the CR register must be between FFh and C0h
(see
– The WDGA bit is set (watchdog enabled)
– The T6 bit is set to prevent generating an imme-
– The T[5:0] bits contain the number of increments
Table 13.Watchdog Timing (f
Notes: Following a reset, the watchdog is disa-
bled. Once activated it cannot be disabled, except
by a reset.
The T6 bit can be used to generate a software re-
set (the WDGA bit is set and the T6 bit is cleared).
If the watchdog is activated, the HALT instruction
will generate a Reset.
5.2.4 Hardware Watchdog Option
If Hardware Watchdog is selected by option byte,
the watchdog is always active and the WDGA bit in
the CR is not used.
Refer to the device-specific Option Byte descrip-
tion.
5.2.5 Low Power Modes
5.2.6 Interrupts
None.
Mode
WAIT
HALT
diate reset
which represents the time delay before the
watchdog produces a reset.
Max
Min
Table
Description
No effect on Watchdog.
Immediate reset generation as soon as
the HALT instruction is executed if the
Watchdog is activated (WDGA bit is
set).
1):
CR Register
initial value
FFh
C0h
WDG timeout period
CPU
= 8 MHz)
98.304
1.536
(ms)
5.2.7 Register Description
CONTROL REGISTER (CR)
Read /Write
Reset Value: 0111 1111 (7Fh)
Bit 7 = WDGA Activation bit .
This bit is set by software and only cleared by
hardware after a reset. When WDGA = 1, the
watchdog can generate a reset.
0: Watchdog disabled
1: Watchdog enabled
Note: This bit is not used if the hardware watch-
dog option is enabled by option byte.
Bit 6:0 = T[6:0] 7-bit timer (MSB to LSB).
These bits contain the decremented value. A reset
is produced when it rolls over from 40h to 3Fh (T6
becomes cleared).
STATUS REGISTER (SR)
Read /Write
Reset Value*: 0000 0000 (00h)
Bit 0 = WDOGF Watchdog flag .
This bit is set by a watchdog reset and cleared by
software or a power on/off reset. This bit is useful
for distinguishing power/on off or external reset
and watchdog reset.
0: No Watchdog reset occurred
1: Watchdog reset occurred
* Only by software and power on/off reset
Note: This register is not used in versions without
LVD Reset.
WDGA
7
-
7
-
T6
-
T5
-
T4
ST72E311 ST72T311
-
T3
-
T2
-
T1
WDOGF
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0
T0
0