I've tried to post this to the PICLIST before, or at least I believe I did, but it came back from some other address with a note saying that it could not be delivered, so now I'm trying again. If I'm mistaken, please excuse me. I wrote: Hello everyone, Does anybody know how to use the PIC16C74 PSP, then please help. I've tried by the book - I've read the data sheets from front to back and back again, I've read the PSP application note, AN579, and the errata sheets A and B. Every register concerned is set accordingly and it still does not work. I can measure CS and WR low pulses, RD high, (RE0, RE1 & RE2) but the PSPIF interrupt flag is not set. I've tried both with and without PSP interrupt enabled, but the PSPIF is not set no matter what. The local Microchip representative have been working on it for about a week now but haven't come up with any useful suggestions yet. There must be somebody out there who have used this feature - or so I hope. Thanks Michael