> -----Original Message----- > From: Tony Duell [mailto:ard.p850...@gmail.com] > Sent: 28 October 2018 18:04 > To: r...@jarratt.me.uk; Jarratt RMA <robert.jarr...@ntlworld.com>; General > Discussion: On-Topic and Off-Topic Posts <cctalk@classiccmp.org> > Subject: Re: DEC 8640 Pinout > > On Sun, Oct 28, 2018 at 5:53 PM Rob Jarratt via cctalk <cctalk@classiccmp.org> > wrote: > > > > I am trying to trace the reason why the CPU on my Pro 350 is > > apparently being constantly reset. I have reached a DEC 8640 chip. > > Does anyone have a pinout for it, perhaps even a datasheet, so I can > > understand what it is supposed to do and whether the pin is an input or an > output? > > > > I've sent the data sheet by private e-mail. > > Have you looked at the Pro380 printset on bitsavers? The reset input on the > J11 chip in that machine comes from the DCOK pin on the power supply (Pin > 1 of the PSU connector). It's also buffered by an 8640 for other bits of the > systen. I would not be surprised if the Pro 350 is similar. > > Are you_sure_ the DCOK pin on the power supply is stable and not > oscillating? >
Thanks for the datasheet. I have to say I am not totally convinced that I have correctly identified the reset pin on the F11 because there seems to be a lot of logic behind it. This particular path I am pursuing now seems a bit more promising though. I have not checked the DC OK pin yet as I wasn't sure which one it was and I was hoping my tracing would take me back to the PSU, but I haven't reached it yet. I suppose I have been assuming that the LED means it is OK, but perhaps it isn't. Hopefully this 8640 will take me closer. When you say it is pin 1 on the connector, which side are you counting from? Thanks Rob
