IEEE488 electrical specs

From: Martijn van Buul (
Date: 2001-04-18 11:49:54


Does anyone have the *electrical* specifications of the IEEE488 bus?
The only piece of information I have is that it uses "multi-drop lines",
which I assume to be equal to an open-collector bus. However, I'd like
to know how much current I have to sink to make things work.

I'm trying to get a working IEEE-488 implementation on a 8051, and I'd
like to know if I can directly tie its I/O pins to the IEEE-488 bus. The
8051 can be configured to use open-collector on its I/O pins, but there
are some culprits. For instance, 3 out of the 4 ports have internal
pull-up resistors, and I'd like to know if that has a serious impact
on the bus. Secondly, these I/O pins can officially sink only 15 mA,
allthough 20mA is not a problem.

(the whole intention is to re-implement Andre's IEEE-to-serial converter,
 using off-the-shelf components. Andre used several chips which aren't
 really *that* easy to obtain, like RIOTs)

    Martijn van Buul - -
	 Geek code: G--  - Visit OuterSpace: 3333
   Kees J. Bot: The sum of CPU power and user brain power is a constant.
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