Subject: Re: mvme147 problems...
To: Frederick W. Koehler IV (Joe College) <email@example.com>
From: Michael Thompson <firstname.lastname@example.org>
Date: 08/17/1998 08:36:54
At 02:25 AM 8/17/98 +0000, Frederick W. Koehler IV (Joe College) wrote:
>One question--I have a six slot backplane, and currently have the
>mvme147 in the same slot the original mvme132 68020 board was in. There
>are two empty slots and then the remaining three slots are filled with
>the tape controller, six port serial board, and finally the winchester
>controller. In between each slot there are a series of jumpers,
>however, there doesn't appear to be a set of jumpers for each slot, only
>in the spaces between slots. This leads me to wonder how exactly the
>backplane is to be jumpered. Should I have jumpers on each side of the
>empty slots? Maybe the hangs I'm getting at iot;t time are from vmebus
The jumpers on the backplane are for Bus Grant and Interrupt Acknowlege.
Some VMEbus boards, like disk controllers, do their own VMEbus I/O instead
of using DMA from the CPU. The I/O board requests control of the VMEbus,
the arbiter on the CPU board releases control of the VMEbus, and then the
arbiter on the CPU sends a Bus Grant signal down the backplane.
There are only 4 Bus Grant levels, and you can have several boards, on
the same Bus Grant level. The Bus Grant signal daisy-chains down the
backplane through each I/O board. If you have an empty slot you break
Backplane manufacturers put jumper pins next to the connectors so you can
jumper across empty slots. Unfortunately the jumpers may be to the right
or left of a slot depending on the manufacturer.
You may also find that some VMEbus boards don't pass on daisy-chain signals
that they don't use. This means that you may have to leave jumpers on
even when a board is in a slot.
If the boards are side-by-side without an empty slot between the CPU and the
VMEbus boards you may not need any jumpers. That might be worth a try.