On Tue, 14 Apr 1998 21:41:47 -0500, James & Ili wrote: > Does anyone have a wiring diagram to make the adapter for programming > the C756 with the Picstart Plus. I think $129 is a little high for an > adapter! I suspect it takes more than just a rewiring. The 17C756 is programmed in a completely different way than all the other PIC micros. It has two pins that are held high at 13 volts, and the programmer code is actually in the PIC's ROM (so the 17c needs to be running in order to program it). It uses an instruction that none of the other PICs have (TABLWT - Table Write) for writing program instructions to the EPROM. Basically, there are a number of things that need to be done to program the 17c756. You need to put the TEST pin to program voltage (13 volts), and then a usec later put the MCLR pin to program voltage. You start the device clock (oscillator, <= 8 MHz) on pin RA1, and then wait at least 20 instruction cycles for the ROM code to initialize the USART/SCI so it can receive commands. Then you start sending it commands over the serial line. There's a document that describes this whole process in a whole lot more detail, you can get it at http://www2.microchip.com/download/lit/progspec/30274a.pdf. Basically, I suspect the $129 adapter is almost an entirely separate programmer that uses some of the functionality of the main programmer, but extends it to allow for this new way of programming. Later, Jon -------------------------------------------------------------- Jon Hylands Jon@huv.com http://www.huv.com/jon Project: Micro Seeker (Micro Autonomous Underwater Vehicle) http://www.huv.com