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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.
So you still haven't got the watchdog right yet! Again, the two possibilities are:
1. The watchdog is somehow getting disabled; 2. Your watchdog update scheme is flawed so that it can keep the watchdog running despite the program being stuck in a loop! 3 while the WD is now fed in the main it is still fed in the ISR as well. 4) the updated code is not what is in the chip
Erik
Not a C51 guy, but is it possible that only the "watchdog reset bit" was disabled (assuming that like in a LPC2400, the watchdog cannot be disabled once started) as some point ?