I have a problem with resetting/starting a 90S2343 processor (exact printed on the chip: ATMEL 9819 AT90S2343 10PC).
When I power up my (simple) app, the processor doesn’t start (I use the internal clock). Puling down the reset line doesn’t help. A short short-circuit of the power lines does the trick, the processor starts. Also, if I disconnect the power supply en apply it again, it will start too. The power supply is a simple transformer, a bridge, capacitor and a 78L05. It is stable (no ripple). When disconnecting and connecting, the main capacitor isn’t fully discharged yet.
The same problem occurs with the AVR STK 200 evaluation board. To reset/start the processor, I also have to switch the power on, wait for a moment, switch off, wait 1 sec and switch on again. Now the processor starts.
I read the datasheet forwards and backwards three times, but couldn’t find an answer. Can someone tell me what’s wrong with a 78L05 power supply? Are there special reset considerations? Some other idea’s?