Thanks Bob,
Voltages all check out OK. I noticethat on oneofthetwo chips I am using the output on RB0 -RB7 is about 0>4 volts on one chip and >16 on the other ..is this reasonable ?
I am using three boardsto try thechips on. One is a melabs LabX2, couple of weeks ago I plugged this in and reading the manuals (yesreally !) realised that I could do ICP through the ten pin header direct from my epic programmer. I had a simple,single led flashing program working and could change the timing in circuit .. Great ! so far so good. Then that circuit began to behave as if there was a poor connection sometimes it didn't work an pressing the chip eould restart it, gradually it died altogether. I then built my "Christmas star" PCB which has the d and c ports connected to darlingtons to switch the - side of the leds and port D connected via darlingtons to reed relays to swotch the + sides of the leds which are in a matrix with diodes. I buit a ten pin header into this pcb connected as per the melabs board to enable me to ICP. This part of the circuit I have never got to work so i programmed the 877 direct and the circuit worked like a dream with main power from a car battery charger (to power all the leds) with a 7405 providing the 5 volts for the 877 circuit (I have since tried it with a completely independent 5 volt supply from another board). Then came the disaster ! whilst reprogramming I inserted the 877 into the pcb one pin out of alignment and the whole thing died.Replacing the 877 and the 7805 did nothing. The only sign of life I have ever had sincewas as mentionedin earlier post when touching pin 13 (Xtal) would produce a flashing led where I expected it (albeit with a somewhat variable mark space ratio). Thinking this indicated an oscillator problem I followed the othe piece of advice and inserted a 4m resonator and changed to program (i.e. osc set to xt and 4)
Once again it is absolutely dead. Sorry to bore you with all of this but the full story must some where contain the clue that points to the stupid thing I must have done ! I have had the good night sleep (and the whisky) and tomorrow am off to Brussels for a three day break with wife and friends where I shall sulk a bit more and drink to much wine and Belgian beer ! Many thanks for the trouble you have gone to to keep me sane !
cheers David