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atod
January 20th, 2011, 03:59 PM
Folks

I cracked open some of my N* boards today. The CPU board accepts a 2708 with modification. Can an adapter be made to use a 2716 in place of a 2708? I'm assuming there is some voltage change. Thanks

litterbox99
January 20th, 2011, 04:30 PM
Here's the pinouts of some common Eprom's

http://www.jrtwine.com/jtwine/arcade/EPROMRef.htm

Hope this helps...

saundby
January 21st, 2011, 12:04 AM
Just about anything similar you'd use will work at 5V and ground, you'd leave the 12V and -5V the 2708 uses unconnected for a 2716. A socket-in-a-socket adapter would be simple.

A0-A9 go straight through, as do O0-O7, Vcc and Vss. Pin 18 (PROGRAM on the 2708 ) will not go through, lift this leg on the adapter socket, tie it to pin 20 (/CS on the 2708 ) to tie both /OE and /CS on the 2716 to that signal. Lift pin 21 on the adapter socket, you want no connection there.

Pin 19, A10 on the 2716, will also be lifted. Tie it either high (5V) or low (GND). If you want to get fancy, you can put a switch on the line to pull it to either high or low, switching between two ROM images.

I think that covers all 24 pins.

atod
January 21st, 2011, 07:22 AM
Thanks folks! This is exactly what I was looking for!

atod
April 4th, 2011, 10:39 PM
Some notes on this. I had to lift pin 21 from the board but jump +5V pin 21 on the EEPROM. I found some AMD 2716 units would read fine without the +5V on pin 21, but the 1977 Intel units I had required the +5V on pin 21.

Also, I tried constructing a socket in socket adapter for my Northstar ZPU board. I purchased some cheap sockets from China. They had very short pins and the whole thing wouldn't stay together well. It wasn't easy to pull the EEPROM either. Finally, I just cut traces on the board and tied pins back and forth with wire wrap. Works great!



Just about anything similar you'd use will work at 5V and ground, you'd leave the 12V and -5V the 2708 uses unconnected for a 2716. A socket-in-a-socket adapter would be simple.

A0-A9 go straight through, as do O0-O7, Vcc and Vss. Pin 18 (PROGRAM on the 2708 ) will not go through, lift this leg on the adapter socket, tie it to pin 20 (/CS on the 2708 ) to tie both /OE and /CS on the 2716 to that signal. Lift pin 21 on the adapter socket, you want no connection there.

Pin 19, A10 on the 2716, will also be lifted. Tie it either high (5V) or low (GND). If you want to get fancy, you can put a switch on the line to pull it to either high or low, switching between two ROM images.

I think that covers all 24 pins.