ST72324 STMICROELECTRONICS [STMicroelectronics], ST72324 Datasheet - Page 54

• Manufacturer Part Number: ST72324
• Description: 5V RANGE 8-BIT MCU WITH 8 TO 32K FLASH, 10-BIT ADC, 4 TIMERS, SPI, SCI INTERFACE
• Manufacturer: STMICROELECTRONICS [STMicroelectronics]

ST72324
WATCHDOG TIMER (Cont’d)
10.1.5 Low Power Modes
10.1.6 Hardware Watchdog Option
If Hardware Watchdog is selected by option byte,
the watchdog is always active and the WDGA bit in
the WDGCR is not used. Refer to the Option Byte
description.
10.1.7 Using Halt Mode with the WDG
(WDGHALT option)
The following recommendation applies if Halt
mode is used when the watchdog is enabled.
– Before executing the HALT instruction, refresh
10.1.8 Interrupts
None.
54/163
1
the WDG counter, to avoid an unexpected WDG
reset immediately after waking up the microcon-
troller.
SLOW
Mode
WAIT
HALT
Description
No effect on Watchdog.
No effect on Watchdog.
OIE bit in
MCCSR
register
0
0
1
WDGHALT bit
in Option
Byte
0
1
x
No Watchdog reset is generated. The MCU enters Halt mode. The Watch-
dog counter is decremented once and then stops counting and is no longer
able to generate a watchdog reset until the MCU receives an external inter-
rupt or a reset.
If an external interrupt is received, the Watchdog restarts counting after 256
or 4096 CPU clocks. If a reset is generated, the Watchdog is disabled (reset
state) unless Hardware Watchdog is selected by option byte. For applica-
tion recommendations see
A reset is generated.
No reset is generated. The MCU enters Active Halt mode. The Watchdog
counter is not decremented. It stop counting. When the MCU receives an
oscillator interrupt or external interrupt, the Watchdog restarts counting im-
mediately. When the MCU receives a reset the Watchdog restarts counting
after 256 or 4096 CPU clocks.
10.1.9 Register Description
CONTROL REGISTER (WDGCR)
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 counter (MSB to LSB).
These bits contain the value of the watchdog
counter. It is decremented every 16384 f
cles (approx.). A reset is produced when it rolls
over from 40h to 3Fh (T6 becomes cleared).
WDGA
7
Section 10.1.7
T6
T5
below.
T4
T3
T2
T1
OSC2
T0
0
cy-