Darnit! UDA50 problem.

From: Tony Duell <ard_at_odin.phy.bris.ac.uk>
Date: Tue Nov 4 08:44:07 1997

On Tue, 4 Nov 1997, Daniel A. Seagraves wrote:

> On Tue, 4 Nov 1997, Tony Duell wrote:
>
> > Remember he has an M9302 terminator. That card will lock up the bus
> > (actually it asserts SACK and keeps it asserted) if the grants are not
> > continuous.
>
> Hmm... That doesn't appear to be happening... Will the CPU run at all
> like that? It boots RT-11 from the RX02 okay...

If you can boot RT11, then the grants must be continuous. Is the RX211
nearer the CPU than the UDA50? Normally, if you've left an NPG jumper in
where you shouldn't have, then the devices past that point fail to do
NPR's correctly.

>
> > On the other hand, having an NPG jumper (the little wire-wrap between pins
> > CA1 and CB1) where you shouldn't have one will cause all sorts of
> > problems. I'm pretty sure that a UDA50 is an NPR (== DMA) device - did you
> > cut the jumper when installing it?
>
> You don't mean the CGJ card, do you? There's something else I'm supposed

No, I mean on the backplane. The little single-height continuity cards
only connect the bus grants. The dual-height ones do the NPG signal as
well, _but_ the jumper I mentioned below is still fitted, since a lot of
older cards do not short CA1 to CB1 themselves, so the wire-wrapped link
is need if you use one of those cards.

> to have screwed with. You mean I have to cut one of the wire-wraps on the
> backplane? That doesn't sound like a good idea... is that correct? When

Absolutely. The wire in question is between pins CA1 and CB1 on the _same_
slot - the slot the control cart of the UDA50 is in. It's a little loop of
wire, and is quite difficult to find the first time.

When I re-wrap them (say after removing a card), I normally use red wire
to make them easier to spot the next time.

> I get to work, look for a wirewrap jumper from CA1 to CB1 on the
> backplane?

The jumper shorts NPGin to NPGout on the slot. It must be fitted on slots
that do not contain options that use DMA (either empty slots, or slots
that contain options that use programmed I/O only - like DL11's, DR11-C's,
etc). It must be removed on slots that contain DMA options (like the
UDA50). If you just pulled a single-height grant card and fitted the UDA50
card, then I am _sure_ you need to cut this jumper as well. Otherwise
NPGin is shorted to NPGout on the UDA50 and the internal grant logic goes
crazy on this card (it won't do any damage, though).

>
>
>

-tony
Received on Tue Nov 04 1997 - 08:44:07 GMT