Need to READ TMS2532 EPROM as if it were a TMS2732 - which pins to swap?  - Page 1
Forum section: electronics / repair

author: Lomax
author_rank: Frequent Contributor
timestamp: September 02, 2025, 04:40:52 pm
content: I was a little bit frustrated to discover that the XGecu T76 EEPROM reader/writerstilldoesn't support the TMS2532 EPROM, which is not that rare in vintage electronics (a synthesizer in my case). But I think I should be able to read the ROMs using the TMS2732 settings, provided I lift and swap some of the pins. I'm not interested in writing anything, onlyreadingthe data. The question is which pins; I've lifted pin 18 on the chip (2532 A11) and connected it to pin 21 on the programmer (2732 A11), and I've lifted pin 21 on the chip (2532 VPP) and connected it to pin 24 on the programmer (2732 VCC).This post on the ClassicCmp mailing listsuggests that's all I need to do -but if I damage these ROMs the synthesizer will never live again, so I thought I'd check here for a second opinion before I press the power button! Also: this is the first time I use my T76 in anger, so I'm doubly hesitant...

author: coromonadalix
author_rank: Super Contributor
timestamp: September 02, 2025, 04:46:27 pm
content: Do ask Xgecu, they may include it ?? it is not a rare item ? unless it can't go up to 25v pp for programming ?have you seen this one ?https://github.com/ricardoquesada/2732-to-2532sold here :https://www.ebay.ca/itm/233499875034some notes found on stardotOn modern CMOS devices, it's less critical as they are rather faster than older parts.For older parts, an EPROM (or ROM) will respond quicker if /CS (/CE) is tied low and you use /OE (output enable) to control the output buffers.The disadvantage of having /CS (/CE) always low is that if the chip has a lower power standby mode, it will never go into this mode. But that's not normally a problem for mains powered systems.For slow parts, using /CS (/CE) may cause problems with timing, depending on how slow the device is.other infos :https://forums.atariage.com/topic/269633-replacing-a-tms2532-with-a-2732/http://www.therealbobroberts.net/mspacrom.htmltl866 adapter:https://www.theoddys.com/acorn/replica_boards/2532-2732_programmer_adapter/2532-2732_programmer_adapter.html

author: Ian.M
author_rank: Super Contributor
timestamp: September 02, 2025, 05:11:06 pm
content: The only potential for damage I can think of is if the T76 attempts to read the chip's JEDEC ID (which really old PROMs/EPROMs didn't have) as this involves putting +12V on A9. Preselecting any 2716 should lock this out, but best to do a dummy run scoping A9 with no chip in the socket to check it really doesn't.Edit: corrected EPROM to preselect

author: chilternview
author_rank: Frequent Contributor
timestamp: September 02, 2025, 05:13:27 pm
content: Quote from: Lomax on September 02, 2025, 04:40:52 pmIf you look at the data sheets page 2 it clearly shows what's expected on the pins for a read operation, so it looks like your method should be ok. Programmers like the XGecu don't handle these old EPROMS because of the high voltages e.g. 21v, 25v - some like the 2708 need 12v as well as 5v. I've made my own programmers for these old EPROMs as there aren;t any commercial programmers for a reasonable price out there.

author: Lomax
author_rank: Frequent Contributor
timestamp: September 02, 2025, 05:42:06 pm
content: Thanks guys! Where would I be without this forum?The software did complain about pin 18 (2732 chip enable) not being connected to anything, but it appeared to read just fine when I chose to ignore thatTried three times and got the same checksum each time.

author: Lomax
author_rank: Frequent Contributor
timestamp: September 02, 2025, 05:56:37 pm
content: Second EPROM also read successfully, three times with identical checksums. This one was only about half full. There's not much in the way of strings to look at, since this synth only has seven segment displays, but there's one bit where it goes "ABC.....DEFG.....HIJKL" which looks intentional.

author: agent_power
author_rank: Regular Contributor
timestamp: September 02, 2025, 06:55:46 pm
content: Do you have a known checksum and does it match? Just because you got the same checksum three times doesn't mean it's the correct one.If I were you I would wire up a socket adapter with the correct pinout for a 2732

author: Lomax
author_rank: Frequent Contributor
timestamp: September 02, 2025, 08:09:13 pm
content: Quote from: agent_power on September 02, 2025, 06:55:46 pmNo, I do not have a known checksum.Quote from: agent_power on September 02, 2025, 06:55:46 pmOf course. Still good practice though.Quote from: agent_power on September 02, 2025, 06:55:46 pmI used the correct pinout.

author: Lomax
author_rank: Frequent Contributor
timestamp: September 02, 2025, 10:17:14 pm
content: Quote from: Lomax on September 02, 2025, 05:56:37 pmLooking at the schematic I can see why it's only half full: it shows a 16kbit 2716 in place of the 32kbit 2532 that's installed in my machine. But I don't think those are pin compatible!? Perhaps I have a different revision of the PCB to the schematic - or there might be bodge wires on the reverse, which I have yet to take a look at.

author: chilternview
author_rank: Frequent Contributor
timestamp: September 03, 2025, 06:44:43 am
content: Quote from: Lomax on September 02, 2025, 10:17:14 pmSo is it the TI 2716 and TI 2532 you're referring to? The TI 2716 was not the same as the Intel 2716; TI later brought out the 2516 which was.The TI 2716 and 2532 had different pinout. The TI2716 needed -5v on pin 21 and had A10 on pin 20, so a 2532 would not be a drop in replacement.

author: chilternview
author_rank: Frequent Contributor
timestamp: September 03, 2025, 07:18:15 am
content: Here is a good summary of the 2716/2516/2732/2532 saga...https://forums.tomshardware.com/threads/what-is-the-diff-between-a-25x-eprom-and-a-27x-eprom.145638/

author: Lomax
author_rank: Frequent Contributor
timestamp: September 03, 2025, 07:20:27 am
content: Quote from: chilternview on September 03, 2025, 06:44:43 amThe schematic doesn't say, but it must be an Intel 2716 / TI 2516 since it has +5V on pin 21. In fact it's wired exactly like the 2532 next to it.

author: Lomax
author_rank: Frequent Contributor
timestamp: September 03, 2025, 07:31:31 am
content: Quote from: chilternview on September 03, 2025, 07:18:15 amInteresting, thanks. What a messy story!Post #2 says:QuoteMy 2532s are SGS Thompson...

author: chilternview
author_rank: Frequent Contributor
timestamp: September 03, 2025, 07:33:59 am
content: Yes that looks like an Intel 2716 / TI 2516. A bit misleading but pin 21 for a TI 2716 would be -5v.