2716 Eprom Emulator

txmarsh

Does anyone happen to know of an emulator for a 2716 eprom? A project schematic for building one would also work.
Thanks!
Tim

kwinn

2716 is a 2K x 8 bit memory chip that can be programmed electrically and erased using UV light. It is a 24 pin chip with 11 bits of address and 8 data bits.
Don't know of an emulator but you could probably use a 2816 eeprom instead. Other options would be a 2K x 8 non volatile (battery backed) ram chip or using a Prop to emulate one or more (up to 16) 2716's.

There may be alternative suggestions if you post a bit more info on what you want to do.

txmarsh

Thanks for the suggestions. I've been writing a lot of motorola 6802 code and buring it to 2716's for an old pinball machine control board I have. I'm just getting tired of the burn... erase... burn routine. Just learned that there were once eprom emulators that would allow you to avoid having to burn eproms during development testing. Basically the box plugged into the rom socket and had a cable connected to your computer. Allowed you to update the code without actually buring roms. Haven't found any such emulator for such an old eprom as the 2716.

Mike Green

As kwinn mentioned, you ought to be able to make a 2716 emulator using a Propeller. There are 11 address lines, 8 data lines, a chip select and maybe an output enable. That's a total of 21 lines so there are plenty of I/O pins free for other things. The 2716 is a pretty slow part and it would only take a few instructions to test for an output enable and change the data lines from input to output mode, then test for a chip select, read the address lines, read a byte from HUB memory and store it in the output register. If you need more speed, you could use an external tri-state buffer and let that handle the output enable. A tri-state buffer could also boost the output voltage and isolate the Propeller from the 5V logic.

localroger

What Mike Green said. You would probably have to write it in PASM but it would be a very simple program to map 2K of Hub RAM to be the "ROM." Then you could write the programmable loader in Spin and run it in another cog to update the contents.

The old-school emulators were pretty low level, they used RAM chips and TTL logic to switch the bus signals from the ROM bus to the controlling device bus for programming.

RobotWorkshop

It shouldn't be too hard to build one. You can get the +5v supply and ground from the 2716 socket for power. (Ignore the -5V and +12V since those are only required for a real 2716 EPROM)

What I would consider if I were building one is to use a standard SRAM like the 6116 or 6264 chips. It could look as read only to the host but you can use the Propeller to write to it. Just use a couple latches/buffers to isolate which one is controlling the SRAM. I found some schematics that may get you started:

http://www.devrs.com/e/tools.php

http://www.devrs.com/e/files/ee256.gif

http://www.devrs.com/e/files/ee4096.gif

Also a nice reference on EPROM's

http://wiki.xtronics.com/index.php/How_EPROMS_Work

Hope this helps,

Robert

txmarsh

Thanks for all the information. I made a promise (to myself... so easily broken) that I would start to limit project creep... such a dilemma... do I put my current project on hold and design an emulator (for the benefit of my current project) or do I just keep of the burn - UV erase - burn lifestyle????? ; )

kwinn

IMHO you would be better off using the prop (protoboard) to emulate the 2716. Much simpler hardware, much faster than burning an eprom, and more flexible since it can also be used for other things such as tracing and debugging.