Vintage Parallax ROM Emulator working again.....
RobotWorkshop
Posts: 2,307
Hello,
I work on a lot of odd projects·and one older project that i've been working on lately uses some old 80C32 based CPU boards.· When I got them it came with an old Parallax ROM Emulator (from 1991) that does 2764, 27128, and 27256 EPROM chips.· The problem was that the modular cable and DB-25 parallel port connetor had been long lost.· The last time I looked at it was a couple years ago and at that time I had scoured the Internet, contacted Parallax, and anyone who may know what the pinout was for the missing cable.· I had a couple people respond but none of the info proved useful.· This weekend I pulled it out and decided to figure it out.· Luckily on the 5.25" disk with the utility to transfer the HEX image there was a small example source program in 8088 assembly which (after walking through the code) showed·which pins it was trying to use on the Parallel port.· It showed that it used a total of 6 pins.· That is all the pins on the modular cable connector.· After pulling off the plastic protective cover on the emulator I was able to figure out what lines should go to each connection.· I am happy to say that after making up a cable with my new pinout in hand the Emulator WORKS!· I had doubts since I tried it on a laptop running Windows XP but even in a CMD window the old DOS program runs fine!· One more project wrapped up.
So, to save anyone else some major headache if they lose the cable here is the pinout.· As far as I know this is the only place it is documented.....
Looking at the end of the open connector:· (catch down toward PCB and actual contacts on the top)
modular - DB-25
1 (D0) to pin 2· (data bit to clock into HC595)
2 (D1) to pin 3· (clock new bit into HC595)
3 (D2) to pin 4· (move byte from HC595 to RAM and increment pointer to next memory location)
4 (D3) to pin 5· (keeps host reset and tri-states host)
5 (BUSY) to pin 11· (feedback from HC595) used to determine correct port
6 (GND) to pin 25· (ground)
This pinout is unlike any that people had mentioned in the past and is the only one that seems to work.·
Hope this helps someone else out there.
Robert
·
I work on a lot of odd projects·and one older project that i've been working on lately uses some old 80C32 based CPU boards.· When I got them it came with an old Parallax ROM Emulator (from 1991) that does 2764, 27128, and 27256 EPROM chips.· The problem was that the modular cable and DB-25 parallel port connetor had been long lost.· The last time I looked at it was a couple years ago and at that time I had scoured the Internet, contacted Parallax, and anyone who may know what the pinout was for the missing cable.· I had a couple people respond but none of the info proved useful.· This weekend I pulled it out and decided to figure it out.· Luckily on the 5.25" disk with the utility to transfer the HEX image there was a small example source program in 8088 assembly which (after walking through the code) showed·which pins it was trying to use on the Parallel port.· It showed that it used a total of 6 pins.· That is all the pins on the modular cable connector.· After pulling off the plastic protective cover on the emulator I was able to figure out what lines should go to each connection.· I am happy to say that after making up a cable with my new pinout in hand the Emulator WORKS!· I had doubts since I tried it on a laptop running Windows XP but even in a CMD window the old DOS program runs fine!· One more project wrapped up.
So, to save anyone else some major headache if they lose the cable here is the pinout.· As far as I know this is the only place it is documented.....
Looking at the end of the open connector:· (catch down toward PCB and actual contacts on the top)
modular - DB-25
1 (D0) to pin 2· (data bit to clock into HC595)
2 (D1) to pin 3· (clock new bit into HC595)
3 (D2) to pin 4· (move byte from HC595 to RAM and increment pointer to next memory location)
4 (D3) to pin 5· (keeps host reset and tri-states host)
5 (BUSY) to pin 11· (feedback from HC595) used to determine correct port
6 (GND) to pin 25· (ground)
This pinout is unlike any that people had mentioned in the past and is the only one that seems to work.·
Hope this helps someone else out there.
Robert
·