1 chip EEPROM programmer for the replica 1/Apple 1

What have you built or do you want to design to go with your replica 1

1 chip EEPROM programmer for the replica 1/Apple 1

Postby vbriel » Feb Thu 02, 2006 8:38 pm

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
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Postby programsynthesiser » Mar Wed 29, 2006 9:24 pm

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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Postby cheese1113 » Apr Tue 11, 2006 1:35 am

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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Postby vbriel » Apr Tue 11, 2006 7:30 am

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.
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Postby cheese1113 » Apr Tue 11, 2006 12:36 pm

Thanks Vince!
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Postby cheese1113 » Apr Tue 11, 2006 3:21 pm

Max Wooden
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Postby vbriel » Apr Tue 11, 2006 4:29 pm

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
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Postby cheese1113 » Apr Tue 11, 2006 4:38 pm

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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Postby Kallikak » Apr Wed 12, 2006 2:05 am

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.
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Postby cheese1113 » Apr Wed 12, 2006 12:18 pm

Cool! Got any pics? :-)
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Postby cheese1113 » Apr Thu 13, 2006 3:12 pm

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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Postby programsynthesiser » Apr Thu 13, 2006 8:00 pm

Great! Please take pictures as you go on. :)
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humm!

Postby scelbi8h » May Sun 07, 2006 1:40 pm

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? :?
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Postby foresmac » May Sun 07, 2006 7:17 pm

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.
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Re: humm!

Postby Kallikak » May Sun 07, 2006 9:08 pm

scelbi8h wrote: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? :?

When wired up, the EEPROM is just memory at A000 to BFFF. You can write to it any way you like, though depending on the EEPROM chip speed, you have to be a bit careful. With the chips I use, I can write using the monitor without problem, and have burned a couple of ROMs in that way.

When you put the new EEPROM in the ROM socket, what was at A000-BFFF becomes E000-FFFF as required.

foresmac wrote: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?

Yes. NC = No connection, and this connects to the expansion port. The expansion port pinout is on the website (and probably in the documentation too - I forget). You can see how I set it up here: http://school.anhb.uwa.edu.au/personalp ... usader.htm

One thing to look out for if you are new to this (as I was) is the fact that the 5V and ground connections to the 74LS00 are not shown on the schematic. Make sure you connect power to the chip! :) Vince also suggested to me that I test by checking connectivity between the ROM pins and the EEPROM pins. That was helpful in giving me the confidence I had things wired up correctly (though I did initially have a short from a tiny shard of solder that dropped across two tracks, and that stopped the machine from resetting).

Ken
Last edited by Kallikak on Mar Thu 01, 2007 6:42 pm, edited 1 time in total.
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