Assembler Programming Problem

[Pr0f]

If the on board RTC is working - then the I2C from the GAL is working - so it's not your MK2 that's gone duff.

[t0nyt]

If the on board RTC is working - then the I2C from the GAL is working - so it's not your MK2 that's gone duff.

I’ve replaced all the cables and devices & vcc/gnd are good but only the NVRAM/RTC respond/found

The external pins for data/clock run directly off 2 pins of the PCF8583 RTC so in my mind this IC could be damaged?

[Pr0f]

That chip is just a another 'target' for the I2C bus to find - so the fact you can read from that chip suggests the issue lies with either the pins for the I2C output, the resistors R1 and R2 - the 2K2 resistors, or the small PCB track that exists between the connection on the NVRAM/Clock chip and the pins for external devices.

I suspect what may have happened is that connecting to these pins on and off may have caused mechanical damage on the PCB.

[t0nyt]

Will check continuity between IC legs and the pins to start with then

Odd thing is, if it’s mechanical failure, is that yesterday was the first time I’d unplugged/re-plugged cables directly to the pins since I first fitted it as I use an external connector

I guess the other possibility is a failure of my soldering!

[Pr0f]

It might be worth 're sweating' the joints in that case - it could just be a dry joing on that 5 pin header.