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Originally Posted by Mark1960
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I’ve heard that 8255s are in short supply recently, not sure if that is another issue.
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I'd not heard of any problems with getting 8255's, but they are getting on a bit and Intel (Maybe one of the few manufacturers of it) may well have discontinued it by now, and so only stocked by obsolete parts specialists.
- However, the 82C55 CMOS version is still shown as active by Renesas (Who took over Intersil one of previous manufacturers for it)
https://www.renesas.com/us/en/produc...eral-interface
But I'm not sure if 82C55 would always be a direct-fit substitute.
Looking on Octopart, it seems that Rochester (who specialise in buying up old stocks / may also buy up wafer-masks and get re-made with a different prefix like Lansdale did with old Motorola IC's) are now often listed as the manufacturer. But the MR8255 that Rochester list / are also available via Digi-key marketplace are now a rather high £80!
https://www.digikey.co.uk/en/product...aIBxgKyJAXQL5A
But in the UK at least, Cricklewood Electronics are still listing these at a bit more reasonable £12.50+VAT. And a little cheaper (£10) at Silicon-Ark:
https://www.silicon-ark.co.uk/index....ch&search=8255
- Still a bit more than what they use to cost a few decades ago, and rather cheaper direct from the Far East etc, (As little as 50p for (Renesas / ex-NEC) uPD8255 and also 82C55's on Aliexpress) if you take a gamble on whether these have been faked yet.
Although probably a few other smaller components companies still with NOS's that have their own website / are on various online marketplace / auction sites.
Luckily, I think I've still got a few NOS spares / pulls around.
IIRC, they were used on some old PC ISA I/O cards, that I think I've got, but these are probably now worth keeping intact rather than stripping for spares.