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Hi, I use AT89S52 in a project. I send and receive data through TXD, RXD pins to a GSM module for sending SMS to another mobile equipment. I use watchdog facility and the watchdog counter is reset at every 256 counts. My crystal frequency is 11.0592 MHz. It happens once in a while that the uC doesn't respond and remains as if it hangs. Then it has to be RESET again. I doubt whether it happens while serial data reception and sending happens simultaneously. I wrote the program in C using KEIL IDE. My questions are 1) What are the special precautions to be taken in this case?(sending and receiving simultaneously) 2)why this happens even when the watchdog is active? It will be highly appreciated if anybody can give some guidance.
I don't use an external memory. This is as per the application circuit given in the data sheet of DS1232. Is it not true that monitoring the ALE pin is enough to confirm whether the program is running?
It shows that the program is running - but, obviously, that includes when it is running in a loop!!
I think you have misunderstood the purpose of that "example" circuit!
Look again - carefully.
(if you also want others to check it out, then provide a link)
So what, exactly, does ALE indicate in that situation?
Pls see fig 2 www.datasheetcatalog.org/.../DS1232.pdf
The title of that figure is, "PUSHBUTTON RESET" .
It is illustrating how to use the part as just pushbutton reset; connecting the /ST input to ALE effectively disables the watchdog function - unless the processor stops completely!
In my case this is what I wanted. By using internal watchdog I could avoid program stuck due to software issues. But sometimes, may be due to spikes, the processor stopped. I wanted to solve that. monitoring this ALE pin using external watchdog will take care of that.Right?