MC80F0424 Datasheet, PDF (55/135 Pages) List of Unclassifed Manufacturers – 8-BIT SINGLE-CHIP MICROCONTROLLERS

Preliminary
MC80F0424/0432/0448
13. WATCH TIMER
The watch timer generates interrupt for watch operation. The
watch timer consists of the clock selector, 15-bit binary counter,
interval selector and watch timer mode register. It is a multi-pur-
pose timer. It is generally used for watch design.
The bit 0,1 of WTMR select the clock source of watch timer
among sub-clock(32.768kHz), f_XIN÷2, f_XIN÷128 and main-
clock(f_XIN). The f_XIN 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_XIN÷128 of main-clock is used when the single clock
system is organized. In f_XIN÷128 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’s oscillation is enabled by XTEN
bit(PSR1 register), the watch timer by sub clock continues to op-
erate even when the CPU is in the STOP mode. The watch timer
counter can output with period of max 1 seconds at sub-clock.
The bit 2, 3, 4 of WTMR select the interrupt interval divide ratio
selection of watch timer among 16, 64, 256, 1024, 4096, 8192,
16384 or 32768.
The IFWT bit of IFR register is set when watch timer interrupt is
generated. (Refer to Figure 12-4)
WTMR (Watch Timer Mode Register)
W
Bit :
7
6
WTEN
-
R/W R/W R/W R/W R/W
5
4
3
2
1
0
-
WTIN2
WTIN1
WTIN0
WTCK1 WTCK0
ADDRESS: 0F6_H
INITIAL VALUE:0--00000_B
WTEN (Watch Timer Enable)
0: Watch Timer disable
1: Watch Timer Enable
Watch Timer Clock Source selection
00: f_SUB
01: f_XIN ÷ 128
10: f_XIN
11: f_XIN ÷ 2
Watch Timer Interrupt Interval selection
000: Clock Source ÷ 32768
001: Clock Source ÷ 16384
010: Clock Source ÷ 8192
011: Clock Source ÷ 4096
100: Clock Source ÷ 1024
101: Clock Source ÷ 256
110: Clock Source ÷ 64
111: Clock Source ÷ 16
Figure 13-1 Watch Timer Mode Register
WTIN[2:0]
WTCK[1:0]
f_SUB
f_XIN÷128
f_XIN
f_XIN÷2
MUX
Clock Source
Selector
WTEN
Clear
If WTEN=0
÷32768
÷16384
÷8192
÷4096
÷1024
÷256
÷64
÷16
MUX
interval
selector
Figure 13-2 Watch Timer Block Diagram
Watch Timer interrupt
MAR. 2005 Ver 0.2
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