Watchdog Timer Programming
A software trigger relies on a thread of execution to constantly trigger watchdog timer. If the thread is ever halted,
the timer decrements to zero and the board resets. The timer may be programmed from zero to three seconds, in 0.2
second intervals.
The registers described below are used to program the watchdog timer. The register set is located at a base address
of 258h.
Watchdog Timer Register Set
Base +
Address
Write Function
Read Function
4
25Ch
Watchdog Trigger
-
5
25Dh
Watchdog Configuration
Watchdog Configuration Read-back
7
25Fh
Watchdog Enable
Watchdog Status
Watchdog Trigger: Base+4 (Write)
Bit:
7
6
5
4
3
2
1
0
Name:
-
-
-
WDTRIG
-
-
-
-
WDTRIG
Writing a one to this bit triggers the watchdog timer.
Watchdog Configuration: Base+5 (Read/Write)
Bit:
7
6
5
4
3
2
1
0
Name:
WDT3
WDT2
WDT1
WDT0
-
-
-
-
WDT3-0
Watchdog timer reload value. Each internal clock tick decrements the watchdog counter by one from
this value. A tick interval is 0.2 seconds.
Watchdog Enable: Base+7 (Write)
Bit:
7
6
5
4
3
2
1
0
Name:
WDEN7
WDEN6
WDEN5
WDEN4
WDEN3
WDEN2
WDEN1
WDEN0
WDEN7-0 Writing 0x99 to this register enables and loads the watchdog timer with the value in the Base+5
register. Writing any other value to this register disables the watchdog timer.
Diamond Systems Corporation
Poseidon User Manual
Page 99
