Hi,
In a work project, the proto is based on a Siemens 80C517, & the target is an Atmel 89C55. The (minimal) test program : 4 times toggle all bits of a port at 2 Hz, then send 3 characters out the serial port at 9600 Bd. The proto does this (& the full program) fine, but the target will *not* send anything i.e. there is no action on pin 13 (PLCC44). The port bits toggle, so I *did* get the reset & EA connected OK! Apart from the start address, the code is identical.

Can anyone suggest a fix, please?

Regards,

Richard
aslo on rwk@aspark.be