Issue cloning some EPROMs. Is it my programmer? - Page 1
Forum section: electronics / projects

author: Rat_Patrol
author_rank: Frequent Contributor
timestamp: May 11, 2020, 09:35:59 pm
content: Sorry if this is the wrong area. But anyway...I am trying to clone some EPROMs, and I'm wondering if its my programmer causing my grief..I have some TMS27PC256 EPROMs, trying to clone them out. I am working to put them on some ATMEL AT27C256R chips, new from DigiKey.Programmer is an MCUMALL GQ-4X, and an older version, not the new one. I'm also using the programmer adapter they recommended, with the jumper set to 5v.That last part interested me, as Vcc needs to jump to 6.5, and Vpp to 13 for programming. I have NOT put it on the scope yet to check the voltages, but I may play with that yet to see what I get.So I pull the data off the old chip (I have multiple examples, they all seem to read the same), switch over the device on the UI to the ATMEL, blank check, burn chip, verify, and everything seems fine. I install the chip onto the PCB, nothing. I put the old chips back in, works fine.I'm wondering if my budget programmer just isn't going to cut it. Supposedly it can handle these chips, but maybe not. Sure, it seems to read them fine, but maybe it can't program? Thinking of shelling out the money for a Dataman programmer, but I'm not sure if that will fix my issue.The programmer works just fine for cloning other chips, such as the X28C64.Any thoughts are appreciated.

author: amyk
author_rank: Super Contributor
timestamp: May 12, 2020, 01:46:46 am
content: Check the specs of the EPROM you're replacing with that of the original. The circuitry may be designed for a specific speed and even a newer faster one may not work.I would also do a quick "spot check" of a few bytes' worth of content of random addresses using a breadboard, some current-limiting resistors, and LEDs; as you suspect, perhaps the programmer isn't writing the data into them.

author: greenpossum
author_rank: Frequent Contributor
timestamp: May 12, 2020, 02:06:46 am
content: I wonder if there are other differences between the TMS and the AT chip which shouldn't matter but do, like the drive capability of the outputs, or the state of some of the other pins like /OE, or the timing charts. Maybe peruse the respective datasheets?

author: eblc1388
author_rank: Frequent Contributor
timestamp: May 12, 2020, 03:05:18 am
content: Read your source Eprom content, save it to a .bin file. Then read your newly programmed chip and save its content to another bin file. Now compare the two files for content difference and you will know the answer one way or the other.

author: Rat_Patrol
author_rank: Frequent Contributor
timestamp: May 12, 2020, 03:05:21 pm
content: Coming back to this project this morning...These chips are in a PLCC package, so naturally when I took the chips off, I soldered on sockets.After the new chips failing, and the old chips working, I took the old chips out of the sockets, put them right back in, and now they don't work either.I've taken them out and put them back a dozen times, thinking a connection issue, and nothing.

author: amyk
author_rank: Super Contributor
timestamp: May 12, 2020, 11:38:59 pm
content: E S D ?

author: greenpossum
author_rank: Frequent Contributor
timestamp: May 12, 2020, 11:58:39 pm
content: Failing logic chips that are driving the EPROM?

author: coromonadalix
author_rank: Super Contributor
timestamp: May 13, 2020, 12:43:01 am
content: Since they are plcc you need to clean all the leads properly, i use copper wick with flux solder to remove any added solder on the leads, do it fast to avoid over heating and put it back in the socket, sometimes any solder left on the leads will deform the ic socket pins ... i'm doing it often with old plcc84 xilinx cpld without any issues, put sockets on the pcb without problems.Or maybe the plcc socket has bad solders contacts on the pcbIm assuming the circuit worked fine before, but it can or could be damaged by esd too ??

author: Rat_Patrol
author_rank: Frequent Contributor
timestamp: May 13, 2020, 02:28:42 pm
content: I doubt if its ESD, I'm always wearing my grounding strap, work on ESD mats, etc.I have a few examples of this board, with a few of them fully functional, and they all give the exact same issue. I'm down to 1 board fully original and working, and I'm getting really nervous about using it at all, but keeping it for reference.The sockets are 3M brand, and I've used plenty of sockets from this lot before with no issues.This one is kicking my butt...I took an original chip, grabbed the data, then compared it to a programmed Atmel chip, and they are identical. Not sure why it won't work.I then took off the sockets, soldering and re-soldering memory chips directly.Now the OEM chips work, my Atmel replacements do not. So the OEM chips don't like sockets for some reason, and for some reason the new Atmel chips are not working.Oh, as a twist, I grabbed another one of these devices off of eBay, arrived this morning. Its mostly functional (has issues outside of the memory chips), and it's using the exact same Atmel chips I'm trying to use (and they look original), so I'm not sure what is going on.