141
CHAPTER 11 WATCHDOG TIMER
11.2 Watchdog Timer Configuration
The watchdog timer consists of the following hardware.
Table 11-3. Watchdog Timer Configuration
Item
Configuration
Control register
Watchdog timer clock select register (WDCS)
Watchdog timer mode register (WDTM)
11.3 Watchdog Timer Control Registers
The following two types of registers are used to control the watchdog timer.
• Watchdog timer clock select register (WDCS)
• Watchdog timer mode register (WDTM)
(1) Watchdog timer clock select register (WDCS)
This register sets overflow time of the watchdog timer and the interval timer.
WDCS is set with an 8-bit memory manipulation instruction.
RESET input clears WDCS to 00H.
Figure 11-2. Watchdog Timer Clock Select Register (WDCS) Format
Address: FF42H After Reset: 00H R/W
Symbol
7
6
5
4
3
2
1
0
WDCS
0
0
0
0
0
WDCS2
WDCS1
WDCS0
WDCS2
WDCS1
WDCS0
Overflow Time of Watchdog Timer/Interval Timer
0
0
0
2
12
/f
X
(489
µ
s)
0
0
1
2
13
/f
X
(978
µ
s)
0
1
0
2
14
/f
X
(1.96 ms)
0
1
1
2
15
/f
X
(3.91 ms)
1
0
0
2
16
/f
X
(7.82 ms)
1
0
1
2
17
/f
X
(15.6 ms)
1
1
0
2
18
/f
X
(31.3 ms)
1
1
1
2
20
/f
X
(125 ms)
Cautions 1. When rewriting WDCS to other data, stop the timer operation beforehand.
2. Bits 3 to 7 must be set to 0.
Remarks 1. f
X
: Main system clock oscillation frequency
2. Figures in parentheses apply to operation with f
X
= 8.38 MHz
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