Re: DEC 8640 Pinout
SOme history that might come in handy - pbir...@gmail.com March 8th, 2014, 11:37 PM The DEC PDP-11 Unibus Handbook identifies three standard ICs for use when connecting to Unibus lines: Bus Receiver - 8640 Quad NOR Bus Transceiver - 8641 Quad Bus Driver - 8861 Quad NAND It seems to be generally agreed that the 8861 driver/transmitter can be substituted by the 7439 Quad 2 Input NAND Buffer O.C. There seems to be no recognized physical substitute for the 8640, at least in part because it uses the 1 & 8 pins rather than 7 & 14 pins for GND/VCC, respectively (see Figure 1-25). Is that correct? What have folks been doing when needing to physically replace one of these -- substitute from a sacrificial module? For new designs, or rewiring old ones (dead-bug?), is there a generally agreed logical substitute for the 8640? Unibus handbook Figure 1-30 does specify the RC-equivalent input for this IC but I have not as yet tried to cross-walk it against well-known SN74xx-series chips. I imagine that I'm the umpteenth person to encounter this problem, so before I try to rediscover fire I'm hoping that someone else could share their torch of knowledge :->? On Sun, Oct 28, 2018 at 2:19 PM Camiel Vanderhoeven via cctalk wrote: > > 8640 looks like a date code; most dec chip numbers begin with "DC". > > On 10/28/18, 6:53 PM, "cctalk on behalf of Rob Jarratt via cctalk" > 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? > > > > Thanks > > > > Rob > > > >
RE: DEC 8640 Pinout
> -Original Message- > From: Tony Duell [mailto:ard.p850...@gmail.com] > Sent: 28 October 2018 18:15 > To: r...@jarratt.me.uk > Cc: General Discussion: On-Topic and Off-Topic Posts > > Subject: Re: DEC 8640 Pinout > > On Sun, Oct 28, 2018 at 6:10 PM Rob Jarratt > wrote: > > > 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? > > > No idea how the pins are numbered. But the Pro380 printset seems to show > pin 2 as the polarising key.And the pin at the other end of the connector is > logic ground which you must be able to check. > Knowing the 8640 pinout now I was able to trace one of its inputs to the PSU connector, which appears to confirm that DC OK is next to the polarising pin. I can now confirm that DC OK is stable. It seems from my reverse engineering of the schematic that this allows other signals to control the reset state of the F11, but these other signals appear to be driven by clock signals, which is rather confusing at the moment. > That printset includes a schematic of the PSU which might help too. > > -tony
Re: DEC 8640 Pinout
8640 looks like a date code; most dec chip numbers begin with "DC". On 10/28/18, 6:53 PM, "cctalk on behalf of Rob Jarratt via cctalk" 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? Thanks Rob
Re: DEC 8640 Pinout
On Sun, Oct 28, 2018 at 6:10 PM Rob Jarratt wrote: > 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? No idea how the pins are numbered. But the Pro380 printset seems to show pin 2 as the polarising key.And the pin at the other end of the connector is logic ground which you must be able to check. That printset includes a schematic of the PSU which might help too. -tony
RE: DEC 8640 Pinout
> -Original Message- > From: Tony Duell [mailto:ard.p850...@gmail.com] > Sent: 28 October 2018 18:04 > To: r...@jarratt.me.uk; Jarratt RMA ; General > Discussion: On-Topic and Off-Topic Posts > Subject: Re: DEC 8640 Pinout > > On Sun, Oct 28, 2018 at 5:53 PM Rob Jarratt via cctalk > 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
Re: DEC 8640 Pinout
> From: Rob Jarratt > DEC 8640 chip. Does anyone have a pinout for it, perhaps even a > datasheet, That's almost certainly a DS8640; a quad NOR unified bus receiver. Data sheets for the are readily available. Noel
Re: DEC 8640 Pinout
On Sun, Oct 28, 2018 at 5:53 PM Rob Jarratt via cctalk 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? -tony
DEC 8640 Pinout
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? Thanks Rob
