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Last updated on Oct-18-2019 Download

Looking to adapt some boards I have. Questions.

Looking to adapt some boards I have. Questions.
by on (#139110)
I had these made after about three "redos" with the design which work with a 27C322, after someone helped me originally design them. I'm looking to re-use these boards, but I'd like them to fit inside a case (even if I have to wire it in). Are there any other types of chips that could support a 2MB, while being small enough to fit inside a case, I'm thinking like a PLCC32 or if I could use like a tsop adapter III setup and modify the pcb design to accommodate the 27C322 pinout. Any thoughts? If not, no worries, but I'd appreciate it.

The PCB for is a retro system.
Re: Looking to adapt some boards I have. Questions.
by on (#139111)
3V parallel EEPROMs are quite affordable (digikey mentions a 2MiB one for $1.50/1), and come in capacities up to 256MiB ($9/1).

You will have to add voltage shifting (e.g. 74'16245) and a voltage regulator, but 3.3V logic is compatible with 5V TTL signalling as used in older consoles.
Re: Looking to adapt some boards I have. Questions.
by on (#139119)
lidnariq wrote:
3V parallel EEPROMs are quite affordable (digikey mentions a 2MiB one for $1.50/1), and come in capacities up to 256MiB ($9/1).

You will have to add voltage shifting (e.g. 74'16245) and a voltage regulator, but 3.3V logic is compatible with 5V TTL signalling as used in older consoles.


If you are using 3.3V logic in a 5V system at least put some low resistance (~100 ohm) resistors on relevant lines or do level shifting for data as well.
Re: Looking to adapt some boards I have. Questions.
by on (#139120)
I tried to say that :)

To be VERY CLEAR: DO NOT USE a 3V ROM IN a 5V SYSTEM WITHOUT ADDING VOLTAGE SHIFTING.

The easiest options are GTL FET clamps (such as the GTL2008) or voltage buffers such as the 74ALVC16245.