DEC bus transceivers

Eric Smith spacewar at
Tue Oct 25 15:36:00 CDT 2016

On Tue, Oct 25, 2016 at 2:09 PM, Paul Koning <paulkoning at> wrote:

> As for the receiver, it seems that a TI 75140 (adjustable threshold line
> receiver) might do the job.

The high-level input current spec on that is max 100uA, which exceeds the
DEC specification.

One thing everyone seems to be ignoring is that the DEC leakage current
specifications are for Vcc from 0V to 5.25V. In other words, Unibus devices
can't load the bus more when they're not powered.  Almost all proposed
alternatives to the DEC-recommended chips do not meet that requirement.

More information about the cctalk mailing list