MC80F0224 Datasheet, PDF (50/128 Pages) List of Unclassifed Manufacturers – 8-BIT SINGLE-CHIP MICROCONTROLLERS

MC80F0208/16/24
Preliminary
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 f_XIN÷2, f_XIN÷2⁷ 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÷2⁷ of main-
clock(4.194MHz) is used when the single clock system is orga-
nized. In f_XIN÷2⁷ clock source, if the CPU enters into stop mode,
the main-clock is stopped and then watch timer is also stopped.
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 WTIF bit of IFR register is set when watch timer interrupt is
generated. (Refer to Figure 12-4)
WTMR (Watch Timer Mode Register)
W
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--0 0000_B
WTEN (Watch Timer Enable)
0: Watch Timer disable
1: Watch Timer Enable
Watch Timer Clock Source selection
00: -
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_XIN÷128
f_XIN
f_XIN÷2
01
10 _MUX
11
Clock Source
Selector
WTEN
Clear
If WTEN=0
÷32768
÷16384
÷8192
÷4096
÷1024
÷256
÷64
÷16
MUX
interval
selector
Watch Timer interrupt
Figure 13-2 Watch Timer Block Diagram
46
MAR. 2005 Ver 0.2