Hi Folks,

Thanks for all your help - I've found the problem.

I tested a bunch of different chips - all had the same error so not 4620 dependent although I still don't know why the 877 was faultless...

Cause was within my readbyte and writebyte subs for the SHT11 where the SDA line was forced I/O with a Tris statement - this was default TrisB.4 so changing this to C.3 fixed it.

Kind regards,
Bill