Samsung KS57C2308 Manual page 229

KS57C2308/P2308/C2316/P2316
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 and this value enables the watchdog timer, and watchdog timer is set to the longest interval
RESET
because BT overflow signal is generated with the longest interval.
WDMOD
5AH
Any other value
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".
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
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.
BMOD BT Input Clock
(frequency)
x000b
fxx/2
x011b
fxx/2
x101b
fxx/2
x111b
fxx/2
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.
Watchdog Timer Enable/Disable Control
Disable watchdog timer function
Enable watchdog timer function
Table 11-3. Watchdog Timer Interval Time
WDCNT Input Clock
(frequency)
12 12
fxx/(2
9 9
fxx/(2
7 7
fxx/(2
5 5
fxx/(2
stop, and wait signal clears the WDCNT to
RESET,
. When the interrupt request is generated, BCNT
RESET
WDT Interval Time
8) 12
2 fxx/2
8) 9
2 fxx/2 2
8) 7
2 fxx/2 2
8) 5
2 fxx/2 2
TIMERS and TIMER/COUNTERS
Main Clock
8 3
1.75–2 sec
2 2
8 3
218.7–250 ms
2
8 3
54.6–62.5 ms
2
8 3
13.6–15.6 ms
2
Sub
Clock
224–256 sec
28–32 sec
7–8 sec
1.75–2 sec
11-7