Briel Computers Forum

[vbriel]

Here's a 1 chip EEPROM programmer for somebody wishing to copy their EEPROM or create their own data. In keeping with the replica 1 theme, it is a down and dirty solution requiring few connections. All the connections listed on the EEPROM go to their listed connections. A 74LS00 is all that is required to program an EEPROM.

http://www.brielcomputers.com/eeprom.pdf

This attaches to address A000-BFFF and is direct addressing. Simply write to the address to store the data. You should give a slight delay after your write since it takes 200ns to write a byte into an EEPROM. I do a short loop in basic

FOR I=1 TO 2:NEXT I

That does the trick. I tested this circuit out and had 0 errors when writing.

Vince

[programsynthesiser]

Thanks a lot, I remember asking you about something like this. 200ns? That is not bad at all, considering our processor speed.
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It works!

[cheese1113]

I did a search for the M28C64-120P1 on both digikey and jameco; there were no results. Where can I get this chip?
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Max Wooden

[vbriel]

Digikey part #AT28C64-12PC-ND
Jameco part # doesn't exist any more, they want 500+ at a time.

You can use the 28C65 too. pin 1 is ready/busy output, just float the pin.

[cheese1113]

Thanks Vince!
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Max Wooden

[cheese1113]

So this would work too, correct?
https://www.jameco.com/webapp/wcs/stores/servlet/ProductDisplay?langId=-1&storeId=10001&catalogId=10001&productId=40475&searchValue=28c65
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Max Wooden

[vbriel]

Yes, that should work and you don't need a min order like digikey requires. I've tried the 2865 in the replica 1 and it works. The ready/busy pin 1 is used on the 2865 which is a nice feature letting the system know if it is ready or not. My method doesn't need it. I can program the entire 8K in 1 minute then read it back and check for errors in the same time. That is with a basic program. I'll upload that program for anybody who wants to copy over their entire eeprom to a new one so you can mod it.

Vince

[cheese1113]

Sweet, I'll get this ordered up. It'd be kind of fun to make a little pcb for this and have a little cartridge based loading system.
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Max Wooden

[Kallikak]

I'm adding a jumper to mine, so I can have it in either a read-only or writable mode. That way I can use the board to be either an EEPROM burner, an extra 8K of RAM or an extra 8K of ROM. I used a ZIF socket, so swapping the chips in and out is straightforward.

[cheese1113]

Cool! Got any pics?
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Max Wooden

[cheese1113]

Alright I got the chips! One of the nice things about being in California is I can order something from jameco and have it here within 24 hours using the cheap shipping. I pulled a 74LS00 from an apple ][ board I had; the funny thing is I ordered a 1 lb grab bag of 74L series chips from jameco and I didn't get a single 74LS00. I'm gonna try and build this tonight or tomorrow. I'll let you all know how it goes.
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Max Wooden

[programsynthesiser]

Great! Please take pictures as you go on.
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It works!

[scelbi8h]

could you give more details about wriying at memory? I don't understand if I have to write from basic or woz monitor... and if it's from monitor, how can I use that basic loop?

[foresmac]

These may be dumb questions, but what the hell:

I looked at the schematic, and I'm not sure what pins 1 and 26 connect to. NC = no connection?

Also, I assume this is deisgned to work with the 40-pin expansion port, correct?

Thanks.

[Kallikak]