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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 CPU "crashes". When enabled, the program

must write to I/O address &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

DELAY 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 reset chip U14.

Watchdog time is determined by jumper W D. The

following table determ ines the timeout.

Pins Timeout

[1-2] 150 ms

no jumper 600 ms

[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 &E8,0 :' Reset timer

10000 BIT &E4, 0,0 :' Turn off watchdog

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Remote-processing RPC-2300 Manual de usuario Pagina 32