I decided to make a new programmer for the Atmel 1051,2051 & 4051's. I didn't want to have to multiplex any of the lines of the PC parallel port. To do this required increasing the number of i/o lines available from the parallel port. I'd already achieved this by interfacing an 8255 to the parallel port. All that was now needed was to interface the target microcontroller to the 8255. Instead of designing a totally new PCB, I decided to used the existing 8255 PCB and modify the original programmer PCB to match the 26 pin IDC header from the 8255 PCB.
Most of my original programmer power supply could still be used. Pull up resistors needed to be added on the X051 P1 lines. See circuit below.
Photos showing the component and solder sides of the 8255 PCB
Photos showing the modifications to the original programmer PCB to interface to 26 pin IDC header.
Photos showing the 8255 & programmer PCBs interconnected with 26 way ribbon cable. Note added pull up resistors beside zif socket.
Obviously the new 8255 driven programmer requires new software to operate. Download the latest programmer software here. This version includes support for the 4051 and will detect the proccessor.