CHAPTER 9 WATCHDOG TIMER
Preliminary User’s Manual U19014EJ1V0UD
218
9.2 Configuration of Watchdog Timer
The watchdog timer includes the following hardware.
Table 9-1. Configuration of Watchdog Timer
Item Configuration
Control register
Watchdog timer enable register (WDTE)
How the counter operation is controlled, overflow time, and window open period are set by the option byte.
Table 9-2. Setting of Option Bytes and Watchdog Timer
Setting of Watchdog Timer
Option Byte (0080H)
Window open period
Bits 6 and 5 (WINDOW1, WINDOW0)
Controlling counter operation of watchdog timer
Bit 4 (WDTON)
Overflow time of watchdog timer
Bits 3 to 1 (WDCS2 to WDCS0)
Remark
For the option byte, see
CHAPTER 18 OPTION BYTE
.
Figure 9-1. Block Diagram of Watchdog Timer
f
RL
/2
Clock
input
controller
Reset
output
controller
Internal reset signal
Internal bus
Selector
17-bit
counter
2
10
/f
RL
to
2
17
/f
RL
Watchdog timer enable
register (WDTE)
Clear, reset control
WDTON of option
byte (0080H)
WINDOW1 and WINDOW0
of option byte (0080H)
Count clear
signal
WDCS2 to WDCS0 of
option byte (0080H)
Overflow
signal
CPU access signal
CPU access
error detector
Window size
determination
signal
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