tmp88cu74 TOSHIBA Semiconductor CORPORATION, tmp88cu74 Datasheet - Page 56

• Manufacturer Part Number: tmp88cu74
• Description: Cmos 8-bit Microcontroller
• Manufacturer: TOSHIBA Semiconductor CORPORATION

2.4.2
Watchdog Timer Control
watchdog timer is automatically enabled after reset.
(1) Malfunction detection methods using the watchdog timer
Figure 2.4.2 shows the watchdog timer control registers (WDTCR1, WDTCR2). The
watchdog timer output will become active at the rising of an overflow from the binary
counters unless the binary counters are cleared. At this time, when WDTOUT = 1 a
reset is generated, which drives the
the external circuit. When WDTOUT = 0, a watchdog timer interrupt(INTWDT) is
generated.
IDLE mode, and automatically restarts (continues counting) when the STOP/IDLE
mode is released.
Note: Just right before disabling the watchdog timer, disable the acceptance of interrupts
1.
2.
The CPU malfunction is detected at follows.
If the CPU malfunctions such as endless looping or deadlock occur for any cause, the
The watchdog timer temporarily stops counting in STOP mode including warm-up or
Setting the detection time, selecting output, and clearing the binary counter.
Repeatedly clearing the binary counter within the setting detection time
Example:
Example: Sets the watchdog timer detection time to 2
Within WDT
detection
time
Within WDT
detection
time
(DI) and clear the watchdog timer.
If the watchdog timer is disabled under conditions other than the above, the proper
operation cannnot be guaranteed.
DI
LD
LDW
EI
LD
LD
LD
LD
LD
(WDTCR2), 4EH
(WDTCR1), B100H
(WDTCR2), 4EH
(WDTCR1), 00001101B
(WDTCR2), 4EH
(WDTCR2), 4EH
(WDTCR2), 4EH
88CU74-56
RESET
pin low to reset the internal hardware and
21
/fc [s] and resets the CPU malfunction.
;
;
;
;
;
;
;
;
;
Disables the watchdog timer.
Enables interrupt acceptance.
Disable interrupt acceptance.
Clears the watchdog timer.
Clears the binary counters
WDTT ← 10, WDTOUT ← 1
Clears the binary counters (always clear
immediately after changing WDTT)
Clears the binary counters
Clears the binary counters
TMP88CU74
2007-10-19
2003-02-17