Datasheet for a NEC Chip in DEC Professional 350

Tony Duell ard.p850ug1 at
Sun Nov 4 06:41:36 CST 2018

On Sun, Nov 4, 2018 at 12:37 PM Rob Jarratt via cctalk
<cctalk at> wrote:
> I have posted previously about a DEC Pro 350 I am trying to get working
> again. At the moment it seems to be constantly resetting the CPU.
> I have traced one possible path for the cause of this back to a NEC chip for
> which I cannot find a datasheet. It is a 40-pin DIP it is marked "NEC Japan
> 8239K6 D7201C". All I have been able to find is more modern USB host
> controllers.

Almost certainly a uPD7201 multi-protocol (asynchronous and synchronous)
serial chip. I have an NEC data book with it in if all else fails but a google
search for 'uPD7201 datasheet' (no quotes) found sites with the data sheet
to download as a .pdf file.

Quite why that should reset the machine is beyond me....


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