Post by thread:picstart hardware fix for eedata (?)

I was dissapointed to find that the picstart programmer was incapable of programming the data memory on a 16c84. (or at least so I'm told by my microchip rep.) As I have not yet seen a serial mode programmer designed for the mac I had an Idea that may work in hardware. Looking at the programming spec in the databook, all that appears to be different between programming "programme". and data memory is the need to set RB0 to 1 during the control word. I assume that if that is done the picstart and mps16b software will think it is programming prog memory while it is actually reading/writing from the data memory. I'm not quite sure what happens when it tries to write/read addresses above 40h but lets not worry about that just yet. I believe that a simple circuit; RB7 ->[inverted] -> [AND]-> [DIODE]-> RB0 RB2 ->[XOR]-------> RB3 ->[ ] would give the logic required, that is RBO forced to one when a "load data" or "read data" instruction is sent to the chip. At all other times I assume the diode woold look like a high impedence to 0, and not effect the programmer to chip traffic. Before I try this and blow everything up, I invite comments. a) good idea, might work. b) good idea, will not work. c) why bother when there is a much better way of doing it.(remember this needs to work on a mac, and I do not want to buy a more expensive programmer!) All feedback in these catagories appreciated. (As I have not tried it out, please do not destroy your own picstarts.) john