Power on Backplane VME

[santiago...@gmail.com]

Hi, I have a backplane VME Elite of VERO Electronics, 6U with 21
slots; before I apply power (+5 & GND) to the backplane I measured the
resistance betwen those pins and I found about 4.5 Ohms. I looked for
jumpers on the backplane but I couldn´t find any. There is no device
plugged into the backplane.
Any idea about what´s going on will be appreciated. Also, if anyone
have the schematic of the backplane or know a page where I coud find
it, please make me know.
Regards,

Santiago

[BobH]

If I had to guess, I would say the passive termination resistors. If I
remember right each line gets a 330+220 between power and ground.

If you have 32 data and 32 address lines terminated, it would look like
1/(64 * 1/(330+22)) = 8.5 ohms

Bob

[BobH]

> 1/(64 * 1/(330+220)) = 8.5 ohms
>
> Bob

I looked at the VME spec and they recommend 330 + 470 ohm terminators at
either end of the bus, so ammending the previous to

1/(128 * 1/(330+470)) 6.5 Ohms. There may be a few more terminated lines
like the bus control signals and interrupt lines, but I am remembering
most of them as being pull ups rather than the termination. You might
have a shorted capacitor on the backplane, but I kind of doubt it.

Bob

[santiago...@gmail.com]

On 21 feb, 22:58, BobH <WanderingMetalHead.DUMP.S...@yahoo.com> wrote:
> BobH wrote:

Thanks Bob It was really helpfull.