Programming 27C64 with TL866 II - Plus - Page 1
Forum section: electronics / general

author: tony359
author_rank: Frequent Contributor
timestamp: June 25, 2020, 06:22:52 pm
content: Hello all,I have purchased a XGecu Pro programmer (TL866 II Plus) and I am testing it with some eeproms I have. I can successfully read and write an Atmel AT29C010A (so I know the device works) but when it comes to some old Fujitsu MBM27C64-30 I can only read them but not program them.Fogive me my ignorance: I understand these eeproms need to be UV erased before they can be programmed. I do not have an UV lamp but this chip is completely blank and it passes the "blank check" from the software. Still, when I try to program it, it won't work.Am I doing anything wrong here or are those chips defective?Thank you!

author: wraper
author_rank: Unknown
timestamp: June 25, 2020, 06:33:03 pm
content: TL866 II Plus provides up to 18V prigramming voltage, MBM27C64 requires 21V.

author: tony359
author_rank: Frequent Contributor
timestamp: June 25, 2020, 06:35:08 pm
content: Hi WraperI thought the "C" version was only 5 Volts?Edit: no you are right. It says the programming mode is entered when 21V is applied to some pins. So why is the chip listed in the software database??

author: NivagSwerdna
author_rank: Super Contributor
timestamp: June 25, 2020, 06:56:16 pm
content: Quote from: tony359 on June 25, 2020, 06:22:52 pmWhen factory fresh they are already in erased state and can be programmed straight away.I use an old crusty programmer for these devices (Stag PP39) due to the voltage requirement.

author: tony359
author_rank: Frequent Contributor
timestamp: June 25, 2020, 07:12:23 pm
content: Thanks - I now understand the erasing/programming procedure.Is there a more modern alternative to those chips which does not require UV and which does not require 21V?Cheers!

author: NivagSwerdna
author_rank: Super Contributor
timestamp: June 25, 2020, 07:20:22 pm
content: AT28C64B but obviously the pin out will differ so you need to create a small adapter boardIf this is not completely off-piste you might find someone has already done one.

author: tony359
author_rank: Frequent Contributor
timestamp: June 25, 2020, 07:45:22 pm
content: I seeWhat about just giving 21 volts to the VPP pin via an external PSU? If I understand correctly programming is 5V and 21V are needed to enable the program mode. I think I may have seen a video online about that

author: edavid
author_rank: Super Contributor
timestamp: June 25, 2020, 08:13:15 pm
content: Quote from: NivagSwerdna on June 25, 2020, 07:20:22 pmWhy would you need an adapter? The pinout was obviously intended to be compatible.

author: wraper
author_rank: Unknown
timestamp: June 25, 2020, 08:44:51 pm
content: Quote from: tony359 on June 25, 2020, 07:45:22 pmIt's not like you can permanently apply 21V to Vpp. Voltage should change between Vcc and 21V at the right moment.

author: Ian.M
author_rank: Super Contributor
timestamp: June 25, 2020, 09:10:36 pm
content: It probably doesn't even drive Vpp above Vcc as the software knows it cant reach the +21V programming voltage. If it did, it would be theoretically possible to design a Vpp booster which would switch in an external supply when the programmer outputs a Vpp signal >> Vcc. However it would almost certainly be less trouble to get or build (maybe Arduino Mega based), a programmer capable of +21V Vpp

author: tony359
author_rank: Frequent Contributor
timestamp: June 25, 2020, 09:14:29 pm
content: The pinout seems compatible - VPP is missing but I suppose it's not needed anymore?@WraperGot you.In fact I started designing my own programmer some time ago but I could never finish it. It's on my to do list to make a readable schematic and ask for your help!

author: tony359
author_rank: Frequent Contributor
timestamp: June 28, 2020, 03:22:53 pm
content: I happened to watch a video today where a guy was programming those eeprom with the UV window. I could spot the model number from a close up and did a search: that was a 12.75V unit! I went back on my Apple //e ROMs and they too say 12.75V. Shall I assume that those can be successfully programmed with the TL866?

author: NivagSwerdna
author_rank: Super Contributor
timestamp: June 28, 2020, 10:48:27 pm
content: MBM27C64-30 datasheet says... +21V for programmingam2764adc datasheet says.... 12.5V for programmingDifferent question... different answer

author: PCB.Wiz
author_rank: Super Contributor
timestamp: June 29, 2020, 03:13:29 am
content: Quote from: tony359 on June 28, 2020, 03:22:53 pmYes, the Vpp details matter. 12.75V is more modern / common.You might find larger EPROMs that can fit into the same footprint. 27C64 is quite old, and small, so will have EOL'd a long time ago.eg AT27C256R seems to be the cheapest/smallest OTP EPROM currently stockedWinbond used to make MTP EPROMS W27C512 in 28 pins, but for new designs in 2020, you might choose a Flash part instead.