>Hi: > >I've been lurking here for a bit and have checked the various web sites for >information but I need a little help. > >I've worked with the Stamp2 and BasicX-24 but would like to convert one of my >projects to a PIC based board with the intent to actually produce a product. > >What I'm doing is about as plain vanilla as you can imagine. Over a 45 minute >period, the program simply switches various I/O pins HIGH or LOW in >a programmed >sequence that doesn't vary. (The pins activate/deactivate 12V light >circuits/relays through a ULN2803.) Each circuit stays on for a set amount of >time and then turns off. Simple timing loops are used to stretch out the >sequence to 45 minutes. All the pins end up LOW at the end. > >What I want is the maximum number of I/O pins possible to drive the circuits. >The more the merrier. What I'm unclear of is how many of the I/O pins on the >various family of chips have to get used for other overhead uses >such as clock, >etc. (If any?) > >In other words, the 16C5xx chips have 13 I/O pins, the 16C77x have 16, 22, and >33 I/O pins, but how many are actually available on a functioning board? The >number of useable pins is the primary thing I'm looking for. > >Thanks for any help you can offer. > >Mike Tennent Mike: Given your project description, I'd suggest the Allegro UCN58XX serial driver chips. That might even eliminate the 2803, depending on your current requirements. They have up to 30 outputs IIRC. If you use assembly language, a 12C508 can control the whole mess. If you want to stick with Basic, you can use MELabs PicBasic Pro. It only works with the 14-bit core PIC products. The 12C671 is probably the smallest package if that's important; the 16C554 is probably the cheapest. Reg Neale