Thanks for the responses folks. I have implemented the suggestions and the plot as they say, has now thickened ! At first using my original board with the suggested changes and at first ... nothing. Then I inadvertently touched to capacito connected to the pin 8 side of the xtal my led on rb 7 began to flash , the mark space ratio was not 1 to 1 however, the on period being significantly longer. If I touch it with metal the led remains on continuously ! The caps are 22pf all the connections seem OK.
Yes I did try a resonator once before but didn't have a 20 meg (only 4) can I run the 877 20 at 4 if I change the define command. It might be worth a try as there is obviously an oscillator problem of some sort. I also inadvertently tried a 877a and as you say I got nowhere ..in fact the epic wouldn't program it. The chips I am using are new 877 20's
I wish I could use the dear old 16C84 for this job that never gave me all this grief! I am beginning to detest the 877 which is a pity since it is at the heart of a midi decoder I am using in a street organ I am building. Irony is, in that far more complex circuit it works a treat... that's what is so annoying . I shall have to go and have a stiff whisky to calm me down......