Drop-in EEPROM replacement for PROM AM27C256 32 DIP?

[CrazyFin]

I have a HP 8920A with firmware A.16.00.

I am planning to try out to upgrade the firmware to A.18.10 using firmware files found in the HP group in Yahoo groups.

I am trying to figure out what EEPROM I can use as a direct drop-in replacement for the U401 PROM AM27C256 (32 pin DIP) on the signalling board in HP 8920A.
I have been able to find out that I can replace the U1 to U8  PROMS that are AM27C040-120 in PLCC32 with W27E040P-12 PLCC32 EEPROMS.

However, I am not sure what I can replace the U401 PROM that is a AM27C256 32 pin DIP PROM on the signalling board in HP 8920A.

Any suggestions please?

[Kjelt]

Long time ago but IIRC it should be something like a 28C256

[Kjelt]

Are you 100% certain it is 32 pins dip not 28 pins ? 
For 28 pins this is an example for replacement:

https://nl.mouser.com/ProductDetail/Microchip-Technology-Atmel/AT28C256-15PU?qs=sGAEpiMZZMuVhdAcoizlRSQWn4iDi6Wf2J%252bONJX6vDw%3d

[CrazyFin]

Are you 100% certain it is 32 pins dip not 28 pins ? 
For 28 pins this is an example for replacement:

https://nl.mouser.com/ProductDetail/Microchip-Technology-Atmel/AT28C256-15PU?qs=sGAEpiMZZMuVhdAcoizlRSQWn4iDi6Wf2J%252bONJX6vDw%3d

You are right! I checked again and it is indeed a 28 pin DIP... 

The AT28C256-15PU is not fully pin compatible? Looks like the pin 1 and 27 are switched on the AT28C256 versus the AM27C256?


How about the AT29C256?
https://www.mouser.se/datasheet/2/268/Atmel_AT29C256-1180383.pdf

[Kjelt]

The AT28C256-15PU is not fully pin compatible? Looks like the pin 1 and 27 are switched on the AT28C256 versus the AM27C256?

Hmmm you're right, ofcourse you don't have a vpp on a eeprom but the /WE is kindof same functionality abstractly seen.

How about the AT29C256?

Looks ok to me.
Ofcourse this is a flash device which has different properties than an EEprom being:
- less write cycles (typ. 10000 vs a few million for eeprom)
- page erasable sometimes only page writable instead of byte writable like an eeprom

In your case it does not matter since you only want to use it as firmware replacement (eg write once, read many).
But in case of an eprom simulator or something that is written to many many times it might be important.

[CrazyFin]

Ok excellent. Thanks for all the helpful and good advice. 

I will try with AT29C256.

As you wrote, I will just update the firmware so no need of many re-writes.