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TIPI EPROM options


J-Data

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It looks like Unicorn Electronics is completely sold out of the 27C256-150 EPROMS used on TIPI.  Anyone have suggestions for other sources?  I'm tempted to use the Microchip AM27C256R sold by DigiKey, as they are slightly cheaper and band-new rather than 30 year old used or New-Old-Stock parts we've been using.  The down side is they're one time programmable, but I don't think the TIPI EPROM has changed in a while.  Any thoughts?

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26 minutes ago, J-Data said:

It looks like Unicorn Electronics is completely sold out of the 27C256-150 EPROMS used on TIPI.  Anyone have suggestions for other sources?  I'm tempted to use the Microchip AM27C256R sold by DigiKey, as they are slightly cheaper and band-new rather than 30 year old used or New-Old-Stock parts we've been using.  The down side is they're one time programmable, but I don't think the TIPI EPROM has changed in a while.  Any thoughts?

 

It looks like DigiKey has this one.

 

Jameco also has several—all listed as “refurbished”.

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1 hour ago, jedimatt42 said:

I believe there is an eeprom solution that works. I think @InsaneMultitasker used one.

 

 

I used a 29c256 atmel flash chip in place of the EPROM.  I did this only because I couldn't erase or program standard EPROMs with my programmer setup.   I do not remember if I validated the circuit/compatibility at the time but I can say that I didn't make any changes to the card or socket; before anyone pursues this further, it should be properly vetted. 

 

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Thanks for all the feedback.  You guys are the best.  Keep in mind I'm needing a cheap option, like in the $2.00 range.  (Got to keep the TIPI-32K/TIPI-1024K BOM cost down below $20)

 

The issue with the Rochester EPROMs at DigiKey is high unit cost ($3.67) and high minimum order (69 units). 

Futurlec looks great price wise, but delivery in the 3 week time frame (might be OK).

I did reach out to Hodge16/unicorn and he is truly out for now. 

Lots of option on ebay, but none in the $2 range out the door just yet.  I'll keep looking. 

Jameco has exactly what I need and have had very good luck with them, but a bit expensive at $4 a piece. 

Looks like the Atmel 29c256 is EOL/obsolete, but would have been an interesting option. 

 

 

I'll give the Microchip one-time-programmable parts a try and report how they work.  Next spin may go to a PLCC32 rather than the old traditional DIP to save space.

 

By the way, anyone know the minimum EPROM speed grade that will work for TIPI?  I've just been using -150 (150ns propagation delay). 

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2 hours ago, InsaneMultitasker said:

I used a 29c256 atmel flash chip in place of the EPROM.  I did this only because I couldn't erase or program standard EPROMs with my programmer setup.   I do not remember if I validated the circuit/compatibility at the time but I can say that I didn't make any changes to the card or socket; before anyone pursues this further, it should be properly vetted. 

 

 

The 27C256 Vpp ( write voltage ) is 5V when in read mode, and would need to be 13V for write. The 29C256 pin there is *WE, so 5V for read, and 0V for write. TIPI boards that I built, bridge the VCC and PIN1(VPP or WE)... all the other pins are same same.  

 

Appears safe to me. And I've stuck one in just now on my own board, no problem. 

Edited by jedimatt42
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1 hour ago, J-Data said:

So much for the OTP EPROM and no socket.  Could have saved $2. 

Just push the cost on the consumer. I'm just joking (except that's what I would do). It is admirable to try to reduce the cost and make it more accessible. If one time cost of Socket plus 4x OTP PROM is cheaper than socket + EPROM, then PROM still might be a fine solution. Just a bit more of a gamble. I don't plan to develop the ROM more. These things just happen. 

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  • 2 weeks later...

So to follow up, I tried the AT27C256R-70PU from DigiKey.  Programmed fine with the MiniPro TL866 and works great in a TIPI.  Its less expensive than all the other options I could find (~$2), but are one time programmable (no window).  Might be a good option depending on the circumstances, especially if low unit cost is the goal.   

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