KS57C2308/P2308/C2316/P2316 TIMERS and TIMER/COUNTERS
11-7
WATCHDOG TIMER MODE REGISTER (WDMOD)
The watchdog timer mode register, WDMOD, is a 8-bit write-only register located at RAM address F98H–F99H.
WDMOD register controls to enable or disable the watchdog function. WDMOD values are set to logic “A5H”
following RESET and this value enables the watchdog timer, and watchdog timer is set to the longest interval
because BT overflow signal is generated with the longest interval.
WDMOD Watchdog Timer Enable/Disable Control
5AH Disable watchdog timer function
Any other value Enable watchdog timer function
WATCHDOG TIMER COUNTER (WDCNT)
The watchdog timer counter, WDCNT, is a 3-bit counter. WDCNT is automatically cleared to logic zero, and
restarts whenever the WDTCF register control bit is set to “1”. RESET, stop, and wait signal clears the WDCNT to
logic zero also.
WDCNT increments each time a clock pulse of the overflow frequency determined by the current BMOD bit
setting is generated. When WDCNT has incremented to hexadecimal “07H”, it is cleared to “00H” and an
overflow is generated. The overflow causes the system RESET. When the interrupt request is generated, BCNT
immediately resumes counting incoming clock signals.
WATCHDOG TIMER COUNTER CLEAR FLAG (WDTCF)
The watchdog timer counter clear flag, WDTCF, is a 1-bit write instruction. When WDTCF is set to one, it clears
the WDCNT to zero and restarts the WDCNT. WDTCF register bits 2–0 are always logic zero.
Table 11-3. Watchdog Timer Interval Time
BMOD BT Input Clock
(frequency) WDCNT Input Clock
(frequency) WDT Interval Time Main Clock Sub
Clock
x000b fxx/212 fxx/(212 × 28) fxx/212 × 28 × 231.75–2 sec 224–256 sec
x011b fxx/29fxx/(29 × 28) fxx/29 × 28 × 23218.7–250 ms 28–32 sec
x101b fxx/27fxx/(27 × 28) fxx/27 × 28 × 2354.6–62.5 ms 7–8 sec
x111b fxx/25fxx/(25 × 28) fxx/25 × 28 × 2313.6–15.6 ms 1.75–2 sec
NOTES:
1. Clock frequencies assume a system oscillator clock frequency (fxx) of: 4.19 MHz Main clock or 32.768 kHz Sub clock
2. fxx = system clock frequency.
3. If the WDMOD changes such as disable and enable, you must set WDTCF flag to “1” for starting WDCNT from zero
state.