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???
12/10/10 03:14
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#180045 - problem with watchdog of 8253
Friends,

I am sorry, if this is this is a repeat question, but I seek help for this issue.

I am using Atmel's AT89S8253 extensively. Recently I have come across this problem.

Present project uses 11.0592 xtal. The system continuously communicates on 232 @2400bps. It works perfectly well with watchdog disabled, with or without 22pf xtal caps.

The problem starts, the moment, I enable watchdog; the oscillator starts at wrong frequency. I havr not measured freq., but buzzer-beeps are longer, and it stops communicating on 232.

The watchdog is loaded at power as

begin: mov sp,#stacks
orl eecon,#03
call stlwd
mov ie,#92h ;t0,serial enabled
...program follows......


stlwd: mov wdtcon,#0a4h
lwd: mov wdtrst,#01eh
mov wdtrst,#0e1h
ret

Timer0 designed to be 8bit auto-start for 76800Hz, watchdog I am recalling at 2.5msec with help of counter.

Have a Great Time, Always. Thanking you,

List of 8 messages in thread
TopicAuthorDate
problem with watchdog of 8253            01/01/70 00:00      
   oscillator starts at wrong frequency?            01/01/70 00:00      
      Watchdog rate?            01/01/70 00:00      
   example            01/01/70 00:00      
      How to post formatted source code            01/01/70 00:00      
   Not a good way to handle a watchdog!            01/01/70 00:00      
   If I recall            01/01/70 00:00      
   Avoid the AT89S8253...            01/01/70 00:00      

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