EPROM conundrum. - UK Vintage Radio Repair and Restoration Discussion Forum

wave solder · 8th Dec 2021, 12:48 am

I have a strange problem in that I have been trying to copy two Eproms, the ICs being read are Mitsubishi M5M27C100K.

The ICs I am writing to are AMD27C010 which purportedly are drop in replacements.

They are all 200nS parts

The 27C010 programs and verifies correctly, however it does not function in circuit.

I also verified the IC in a different Eprom programmer that I have and it verifies correctly in that too.

Now I wonder what I am missing?

Trigon. · 8th Dec 2021, 1:13 am

Comparing the two datasheets, the functions of pins 2 and 24 appeared to be swapped :-

M5M27C100: 2=OE, 24=A16
MITSS14695-1.pdf

AM27C010: 2=A16, 24=OE
RE_DSHEET_AM27C010-CIM (A)_REI.pdf

Cheers

SiriusHardware · 8th Dec 2021, 1:21 am

Have a look at this thread, especially the fourth post which highlights that two pins are swapped in the pinouts.

http://www.ukvac.com/forum/magic-swo...st1198832.html

When you read the 1000 chips, you are reading them as that type so the reader adopts the correct pinout and reads them correctly.

When you programme the 010s, you are programming them as that type so the programmer adopts the correct pinout for the 010 and programs and verifies correctly.

It only falls over when you then put an 010 into a socket wired for a 1000, because then two of the pins on the 010 are in the wrong place.

You could make an adaptor from a couple of stacked IC sockets - re-route the offending pins on the 010 so they go to the right pins on the 1000 sockets.

Edit: Cross posted with Trigon.

dragonser · 8th Dec 2021, 5:58 pm

Hi,
I think this sounds correct. I think I can remember an addendum on a service manual from the early 1990's that mentioned something about this ?

RogerEvans · 8th Dec 2021, 9:26 pm

Another simple way to patch the offending pins is to bend them outward so that they don't engage with the socket and solder some jumper wires directly to the pins.

Regards,

Roger

Mark1960 · 8th Dec 2021, 9:36 pm

For an eprom you may need to remove it and use it in a programmer again in future. You could stack two sockets into the socket on the pcb, with the two pins removed from the lower of these two sockets, then fit jumper wires from the top socket to plug into the socket on the pcb. If you pick the right diameter solid core wire for the links then you don’t need to solder to the socket on the pcb.

wave solder · 9th Dec 2021, 11:27 am

Thank you for all of the replies, it had been a long day.

Now with the deft use of a soldering iron and some fine wire everything is all working. Thanks so much.

8th Dec 2021, 12:48 am	#1
wave solder Hexode Join Date: Feb 2007 Location: Chesterfield, Derbyshire, UK. Posts: 483	EPROM conundrum. I have a strange problem in that I have been trying to copy two Eproms, the ICs being read are Mitsubishi M5M27C100K. The ICs I am writing to are AMD27C010 which purportedly are drop in replacements. They are all 200nS parts The 27C010 programs and verifies correctly, however it does not function in circuit. I also verified the IC in a different Eprom programmer that I have and it verifies correctly in that too. Now I wonder what I am missing?

8th Dec 2021, 1:13 am	#2
Trigon. Hexode Join Date: Jun 2018 Location: Buckinghamshire, UK. Posts: 387	Re: Eprom conundrum Comparing the two datasheets, the functions of pins 2 and 24 appeared to be swapped :- M5M27C100: 2=OE, 24=A16 MITSS14695-1.pdf AM27C010: 2=A16, 24=OE RE_DSHEET_AM27C010-CIM (A)_REI.pdf Cheers

8th Dec 2021, 1:21 am	#3
SiriusHardware Dekatron Join Date: Aug 2011 Location: Newcastle, Tyne and Wear, UK. Posts: 11,548	Re: Eprom conundrum Have a look at this thread, especially the fourth post which highlights that two pins are swapped in the pinouts. http://www.ukvac.com/forum/magic-swo...st1198832.html When you read the 1000 chips, you are reading them as that type so the reader adopts the correct pinout and reads them correctly. When you programme the 010s, you are programming them as that type so the programmer adopts the correct pinout for the 010 and programs and verifies correctly. It only falls over when you then put an 010 into a socket wired for a 1000, because then two of the pins on the 010 are in the wrong place. You could make an adaptor from a couple of stacked IC sockets - re-route the offending pins on the 010 so they go to the right pins on the 1000 sockets. Edit: Cross posted with Trigon.

8th Dec 2021, 5:58 pm	#4
dragonser Heptode Join Date: Aug 2009 Location: Carshalton, Surrey, UK. Posts: 734	Re: EPROM conundrum. Hi, I think this sounds correct. I think I can remember an addendum on a service manual from the early 1990's that mentioned something about this ? __________________ Regards Peter B

8th Dec 2021, 9:26 pm	#5
RogerEvans Hexode Join Date: Oct 2014 Location: Wiltshire, UK. Posts: 381	Re: EPROM conundrum. Another simple way to patch the offending pins is to bend them outward so that they don't engage with the socket and solder some jumper wires directly to the pins. Regards, Roger

8th Dec 2021, 9:36 pm	#6
Mark1960 Octode Join Date: Mar 2020 Location: Kitchener, Ontario, Canada Posts: 1,294	Re: EPROM conundrum. For an eprom you may need to remove it and use it in a programmer again in future. You could stack two sockets into the socket on the pcb, with the two pins removed from the lower of these two sockets, then fit jumper wires from the top socket to plug into the socket on the pcb. If you pick the right diameter solid core wire for the links then you don’t need to solder to the socket on the pcb.

9th Dec 2021, 11:27 am	#7
wave solder Hexode Join Date: Feb 2007 Location: Chesterfield, Derbyshire, UK. Posts: 483	Re: EPROM conundrum. Thank you for all of the replies, it had been a long day. Now with the deft use of a soldering iron and some fine wire everything is all working. Thanks so much.