Hynix Semiconductor GMS81C5108, User Manual

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GMS81C5108
56 JUNE 2001 Ver 1.0
13. Watch Timer/Watch Dog Timer
This has two functions, one is the interrupt occurrence for
watch time and the other is the signal generation of WDTOUTB for watch dog.
13.1 Watch Timer
The watch timer consists of the clock selector, 21-bit bina-
ry counter and watch timer mode register. It is a multi-pur-
pose timer. It is generally used for watch design.
The bit 1,2 of WTMR select the clock source of watch tim-
er among sub-clock,
f
MAIN
÷
2
7
of main-clock and f
MAIN
of
main-clock. The f
MAIN
of main-clock is used usually for
watch timer test, so generally it is not used for the clock
source of watch timer. The
f
MAIN
÷
2
7
of main-clock is used
when the single clock system is organized. In
f
MAIN
÷
2
7
clock source, if the CPU enters into stop mode, the main-
clock is stopped and then watch timer is also stopped. If the
sub-clock is the source clock, the watch timer count cannot
be stopped. Therefore, the sub-clock does not stop but con-
tinues to oscillate even when the CPU is in the STOP
mode. The timer counter consists of 21-bit binary counter
and it can count to max 64 seconds at sub-clock.
The bit 2, 3 of WTMR select the interrupt request interval
of watch timer among 2Hz, 4Hz, 16Hz and 1/64Hz.
Figure 13-1 Watch Timer Mode Register
Figure 13-2 Watch Timer Block Diagram
WDTCL
Bit : 7 6 5 4 3 2 1 0
WDTEN
WTIN[1:0] (Watch Timer Interrupt Interval Selection)
00: 16Hz
01: 4Hz
10: 2Hz
11: 1/64Hz
WDTEN (Watch Dog Timer Enable Bit)
0: Watch Dog Timer Disable
1: Watch Dog Timer Enable
INITIAL VALUE:-0000000
B
ADDRESS: 0EF
H
WTMR (Watch Timer Mode Register)
R/W R/W R/W R/W
WTCK1 WTCK0 WTIN1 WTIN0
R/W R/W
WTEN (Watch Timer Enable Bit)
0: Watch Timer Disable
1: Watch Timer Enable
- WTEN
R/W
WTCK[1:0] (Watch Timer Clock Source Selection)
00: Sub. Clock (f
SUB
)
WDTCL (Watch Dog Timer Clear Bit)
0: Timer running
1: WDT Clear (Auto reset after 1 cycle)
01: Main Clock (f
MAIN
÷
2
7
)
10: Main Clock (f
MAIN
)
11: -
* When f
SUB
= 32.768 kHz and f
MAIN
= 4.19 MHz
MUX
f
SUB
WDTCL
f
MAIN
21 BIT
2 Bit
16 Hz
Watch Timer
f
MAIN
÷÷÷÷
2
7
WTCK[1:0]
Binary Counter
4 Hz
2 Hz
1/64 Hz
MUX
WTIN[1:0]
WTEN
WTIF
Interrupt
F/F
WDTEN
WDTOUT
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