3 control of watchdog timer, 4 programming notes – Epson S1C88650 User Manual
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EPSON
S1C88650 TECHNICAL MANUAL
5 PERIPHERAL CIRCUITS AND THEIR OPERATION (Watchdog Timer)
5.3.3 Control of watchdog timer
Table 5.3.3.1 shows the control bits for the watchdog timer.
Table 5.3.3.1 Watchdog timer control bits
SR R/W
Address Bit
Name
Function
Comment
1
0
00FF40 D7
D6
D5
D4
D3
D2
D1
D0
WDEN
FOUT2
FOUT1
FOUT0
WDRST
TMRST
TMRUN
Constantly "0" when
being read
1
0
0
0
0
–
–
0
R/W
R/W
R/W
R/W
R/W
W
W
R/W
Enable
On
Reset
Reset
Run
Disable
Off
No operation
No operation
Stop
Watchdog timer enable
FOUT frequency selection
FOUT output control
Watchdog timer reset
Clock timer reset
Clock timer Run/Stop control
FOUTON
FOUT2
1
1
1
1
0
0
0
0
FOUT1
1
1
0
0
1
1
0
0
FOUT0
1
0
1
0
1
0
1
0
Frequency
f
OSC1
/ 1
f
OSC1
/ 2
f
OSC1
/ 4
f
OSC1
/ 8
f
OSC3
/ 1
f
OSC3
/ 2
f
OSC3
/ 4
f
OSC3
/ 8
WDEN: 00FF40H•D7
Selects whether the watchdog timer is used
(enabled) or not (disabled).
When "1" is written: Enabled
When "0" is written: Disabled
Reading:
Valid
When "1" is written to the WDEN register, the
watchdog timer starts count operation. When "0" is
written, the watchdog timer does not count and
______
does not generate the interrupt (NMI).
At initial reset, this register is set to "1".
WDRST: 00FF40H•D2
Resets the watchdog timer.
When "1" is written: Watchdog timer is reset
When "0" is written: No operation
Reading:
Constantly "0"
By writing "1" to WDRST, the watchdog timer is
reset, after which it is immediately restarted.
Writing "0" will mean no operation.
Since WDRST is for writing only, it is constantly set
to "0" during readout.
5.3.4 Programming notes
(1) When the watchdog timer is being used, the
software must reset it within the cycles selected
by mask option.
(2) Do not execute the SLP instruction for 2 msec
______
after a NMI interrupt has occurred (when f
OSC1
is 32.768 kHz).
(3) Because the watchdog timer is set in operation
state by initial reset, set the watchdog timer to
disabled state (not used) before generating an
______
interrupt (NMI) if it is not used.
(4)
______
The NMI generation cycles in the watchdog
timer mask option list represent maximum
values. A maximum minus (
on the watchdog timer reset timing. For
example, when 131072/f
OSC1
is selected by
______
mask option, the actual NMI generation cycle is
within the range of 98304/f
OSC1
to 131072/f
OSC1
seconds.