Remote-processing RPC-2350 Uživatelský manuál stáhnout pdf (Strana 55)

CHAPTER 12 WATCHDOG TIMER

12-1

Figure 11-1 Watchdog timer jumper

CHAPTER SYNOPSIS

 Uses for a watchdog timer

 Cautions using watchdog

DESCRIPTION

WATCHDOG TIM ER CH APTE R 12

A watchdog timer is used to reset the RPC-2350 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

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 0 and disabled by writing a 0 to the same location.

The timer is reset by any access (read or write) to I/O

address &E8.

The AIN com mand, in conjunction w ith the SPI port,

access this address. Thus, executing either an AIN or

SPI function also resets the watchdog timer, if enabled.

The watchdog timer is part of a voltage monitor and

reset chip U14.

Watchdog time is determined by jumper W 1. Use the

following table to set a timeo ut.

W1 Pins Typical

timeout

Range

[1-2] 1.2 sec. 500 mS to 2 Sec.

no jumper 600 ms 250 mS to 1000 mS

2-3 150 ms 62.5 to 250 mS

WARNING:

Once the watchdog timer is enabled, it can only be

disabled by a BIT &E4,0,0 in the program . If the

watchdog timer is running and the program stops for

any reason (program error or < Esc> key hit), the

card will reset. You can recover the program by

typing UNNEW.

PROGRAM EXAMPLES

The following program fragments enable the watchdog

timer, reset it while the program is running, and then

disables it.

100 OUT &E4,1 :'Turn on watchdog

5000 OUT &E8,0 :'Reset timer

7000 A = AIN(N) :’Reset timer

10000 OUT &E4,0 :'Turn off watchdog

1 2 ... 50 51 52 53 54 55 56 57 58 59 60 ... 82 83

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