S1C6S3N2 TECHNICAL SOFTWARE
EPSON
II-23
CHAPTER 5: PERIPHERAL CIRCUITS (Watchdog Timer)
WDRST
: Watchdog timer reset (07FH.D3)
This is the bit for resetting the watchdog timer.
When "1" is written:
Watchdog timer is reset.
When "0" is written:
No operation
Read-out:
Always "0"
When the watchdog timer is used for the reset function, the
software must reset the watchdog timer within 3 seconds.
Operation restarts immediately after the watchdog timer is
reset.
Ordinarily, this routine is incorporated where periodic
processing takes place, such as in the timer interrupt rou-
tine, to detect program overrun, for instance when the
watchdog timer processing is bypassed.
In this case, timer data (WD0–WD2) cannot be used for timer
applications.
The watchdog timer operates in the halt mode. If the halt
status continues for 3–4 seconds, the initial reset signal
restarts operation.
When the timing flag ("0.5-sec flag") is set in the T2Hz inter-
rupt processing routine "TI2", the watchdog timer will be
reset every second.
When the routine "basic timer 'CK'" for the timer is executed
every second on the second, the watchdog timer will be reset
every second on the half-second.
Note
Example of reset
processing for
watchdog timer
Specifications
n sec
n.5 sec
(n+1) sec
(n+1).5 sec
"CK" is executed
"CK" is executed
Watchdog timer
is reset
Watchdog timer
is reset
Time
Fig. 5.1.1
Timing chart
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