J-Data Posted February 26, 2021 Share Posted February 26, 2021 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? Quote Link to comment Share on other sites More sharing options...
+Lee Stewart Posted February 26, 2021 Share Posted February 26, 2021 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”. 1 Quote Link to comment Share on other sites More sharing options...
+Lee Stewart Posted February 26, 2021 Share Posted February 26, 2021 Also, at Futurlec and ABRA. ...lee 1 Quote Link to comment Share on other sites More sharing options...
atrax27407 Posted February 26, 2021 Share Posted February 26, 2021 Have you tried Hodge16 (Unicorn's eBay identity)? 1 Quote Link to comment Share on other sites More sharing options...
+arcadeshopper Posted February 26, 2021 Share Posted February 26, 2021 I can do eprom updates for you I have them in my store also hummingbird does them as well. Sent from my LM-V600 using Tapatalk 1 Quote Link to comment Share on other sites More sharing options...
+jedimatt42 Posted February 26, 2021 Share Posted February 26, 2021 I believe there is an eeprom solution that works. I think @InsaneMultitasker used one. 1 Quote Link to comment Share on other sites More sharing options...
+Ksarul Posted February 26, 2021 Share Posted February 26, 2021 There are oodles of these on eBay. I have bought about a thousand of them from various sellers over the years--and most of them were good once cleaned and erased. 1 Quote Link to comment Share on other sites More sharing options...
+InsaneMultitasker Posted February 26, 2021 Share Posted February 26, 2021 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. 3 Quote Link to comment Share on other sites More sharing options...
J-Data Posted February 26, 2021 Author Share Posted February 26, 2021 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). Quote Link to comment Share on other sites More sharing options...
+jedimatt42 Posted February 26, 2021 Share Posted February 26, 2021 @J-Data, I did just release an update to the ROM a few days ago. Quote Link to comment Share on other sites More sharing options...
+jedimatt42 Posted February 26, 2021 Share Posted February 26, 2021 (edited) 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 February 26, 2021 by jedimatt42 2 Quote Link to comment Share on other sites More sharing options...
J-Data Posted February 27, 2021 Author Share Posted February 27, 2021 1 hour ago, jedimatt42 said: @J-Data, I did just release an update to the ROM a few days ago. So much for the OTP EPROM and no socket. Could have saved $2. 1 Quote Link to comment Share on other sites More sharing options...
+jedimatt42 Posted February 27, 2021 Share Posted February 27, 2021 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. 1 Quote Link to comment Share on other sites More sharing options...
+jedimatt42 Posted February 27, 2021 Share Posted February 27, 2021 You can use pretty slow chips. I think the time between the 9900 asserting address and read operation signals until the data must be ready is 650ns. 1 Quote Link to comment Share on other sites More sharing options...
+Ksarul Posted February 27, 2021 Share Posted February 27, 2021 Here's one I've bought from before, but they are 200nS chips. 130 of them for $260 plus about $20 shipping--but he also accepts reasonable offers. Most TI hardware has no trouble at 250nS, some will work at even slower rates. IIRC, most original TI DSR ROMS were 350nS parts. . . 1 Quote Link to comment Share on other sites More sharing options...
atrax27407 Posted February 27, 2021 Share Posted February 27, 2021 Hodge16 has the27C256-250ns chips for $2.99 plus $3.99 shipping. If you ask them, they will usually combine shipping so it might be worthwhile for a few chips. They also have 27256-250ns chips for $2.49 (same deal on shipping). Quote Link to comment Share on other sites More sharing options...
J-Data Posted March 11, 2021 Author Share Posted March 11, 2021 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. 1 Quote Link to comment Share on other sites More sharing options...
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