Remote Processing RPC-2300 - Manual (Page 32)

WATCHDOG TIMER CHAPTER 11
Page 30 RPC-2300
Figure 11-1 Watchdog timer
DESCRIPTION
The watchdog timer is used to reset the SBS-2300 if the
program or C PU "cr ashes". When enabled, the program
must write to I/O addr ess &E8 to avoid a reset. T he
timeout is adjustable for 150 ms, 600 ms, or 1.2
seconds.
The watchdog should be disabled when using INPUT and
DEL AY statements. Also, loops which do not end
quickly or are of indeterminate duration should be
avoided unless a timer reset pulse is included. An
example of an indeterminate loop is one that waits for a
port condition to change.
The watchdog is enabled by writing a 1 to address &E4,
bit 1 and disabled by writing a 0 to the same location
(use the BIT statement to do this). The timer is reset by
a write of any data to I/O address &E 8.
The watchdog timer is part of a voltage monitor, battery
backup controller, and r eset chip U14.
Watchdog time is determined by jumper W D. The
following tab le determ ines the timeo ut.
Pins Timeout
[1-2] 1 5 0 m s
no jumper 6 0 0 m s
[2-3] 1.2 seconds
PROGRAM EXAMPLES
The following program fragments enable the watchdog
timer, reset it while the program is running, and then
disables it.
100 BIT &E4, 0,1 : ' Turn on watchdog
.
.
.
5000 OUT &E 8,0 :' Reset timer
.
.
.
10000 BIT &E4, 0,0 : ' Turn off watchdog