After playing with my sample 90S1200 chip I decided to order a bunch of 1200's 2313's and 8515 chips. Unfortunately I ordered the 'A' version of the 1200 - which is pre-programmed to use an internal RC clock instead of an external crystal. So, I had to make this programmer to re-program all those chips! Although I have not used the programmer since I built it, it will come in handy if I ever want to sell chips and need to protect the code from being readable: Clearing the SPIEN bit disables the programming interface. Once that bit is cleared, a whole chip erase must be done before the internal memory can be accessed via the SPI or parallel programming interface.
The source is very small and there is a GIF file with the schematic. Read the source for details on voltage, etc.
Note there is no crystal on the left chip (the programmer) - that is because that was one of the 1200A's.