EEPROM Memory Programming question - Page 1
Forum section: electronics / projects

author: Crambone
author_rank: Frequent Contributor
timestamp: March 29, 2025, 03:12:29 am
content: Hello all I am trying to program 4ea FUJITSU MBM27128-25 EEPROMS. I am using a XGecu TL866 II PLUS and trying to put a HEX file on each one. I can see the EEPROM is Blank but when I try to program the new text I’m getting the following message.

author: edavid
author_rank: Super Contributor
timestamp: March 29, 2025, 04:20:51 am
content: They are EPROMs, not EEPROMs.The required programming voltage is 21V, but your screenshot shows VPPof 18V, which won't work.

author: Benta
author_rank: Super Contributor
timestamp: March 29, 2025, 11:29:45 am
content: Why is Vdd Write 5.5 and not 5.0 V?

author: Crambone
author_rank: Frequent Contributor
timestamp: March 29, 2025, 11:43:46 am
content: Thanks for all the reply’s the voltages are what appeared when I selected that specific EPROM from the program list. I will set Vpp to 21v and Vdd to 5v and try that.

author: PGPG
author_rank: Frequent Contributor
timestamp: March 29, 2025, 11:56:39 am
content: It says "Programming Flash ...".Flash are certainly programmed different way than EPROMs and EEPROMs.If it is only just text and really says "Programming EPROM..." then:It says: Buffer Data: 0x00 Verify: 0xC3.As blank element has all bytes 0xFF than when after trying to program 0x00 it is read as 0xC3 it means that some bits got programmed enough to be read as zeros, but not all.What can be the reason:- too short programming pulse,- too small VPP voltage,- incorrect algorithm (if remember well (it was 1988 when I was doing it) some EPROMs were programmed by single 50ms pulse, others (to make task faster) by serie of 1ms pulses with verification after each pulse and when read correct than extra 5ms pulse to ensure that programming is not too weak.

author: Crambone
author_rank: Frequent Contributor
timestamp: March 29, 2025, 01:11:46 pm
content: Ok looking at the datasheet I see 50 msec timing at 21v. This is my first time using a programmer so I’m trying to absorb as much as my old brain can. Thanks everyone!

author: squadchannel
author_rank: Frequent Contributor
timestamp: March 29, 2025, 01:23:13 pm
content: xGecu Software does not change the string displayed for the type of device being programmed, whether it is an EPROM or an EEPROM, it will all display "FLASH".error message means: "expected 0x00, but the verify result is 0xC3."it is a UV-EPROM, so I think it is not erased. maybe it can be erased if left in the sun for a few days.

author: edavid
author_rank: Super Contributor
timestamp: March 29, 2025, 01:54:27 pm
content: Quote from: squadchannel on March 29, 2025, 01:23:13 pmNo, that's not it. EPROMs erase to 0xFF, and OP said it passed the blank check. The problem is probably the programming voltage.

author: Crambone
author_rank: Frequent Contributor
timestamp: March 29, 2025, 05:39:13 pm
content: Ok I cleared the EPROM via a UV eraser for 60 minutes. I check the chip on the program and it says Blank. I then load the code and hit Program and I’m getting the following. I have set up an external Dc supply at 21v .250amp + on Pin1 and - on Pin14 as the program is only showing 18v as the highest I can select? Also it doesn't give an option of 50ms for puls speed it shows in ua and the range is 5 to 200ua.I tried at different puls speeds but get the same results but at least with the 21v it does Flash but then fails.I was wondering if maybe I could select another EPROM that may have a different setup and will allow a slower pulse speed? I’m just not sure what EPROM I can look at, again it’s my first time doing this.Here are a few pics of what I’m seeing.Maybe my File load options or other settings are wrong?

author: HwAoRrDk
author_rank: Super Contributor
timestamp: March 29, 2025, 05:50:48 pm
content: According totheir website, the TL866II Plus doesn't support VPP higher than 18V. Apparently the older non-Plus version supported 21V.I don't know why they would claim to support the MBM27128 if it requires +21V VPP.

author: Crambone
author_rank: Frequent Contributor
timestamp: March 29, 2025, 08:36:05 pm
content: Agree so I used a power supply to support the 21v.