[time-nuts] HP Z3801A info needed - 1PPS interface

[Francis Grosz]

Ed,

     The PPS signal on the DB-25 connector is indeed pECL.  And you might
want to look at the TI 65ELT23 pECL to TTL converter instead of a
comparator.  It's made specifically for this, you get two in an 8 pin
package, and typical prop delay is 3.5 ns.  They run $4 at Mouser.  That's
what I used.

        Francis Grosz


On Tue, Oct 5, 2021 at 3:11 PM ed breya <eb at telight.com> wrote:

> I've been doing a bit more work on the far from finished Z3801A project,
> trying to button things up. It has been sitting for years all opened up
> (but running), with temporary pieces and cables and wiring hanging out
> every which way. The next piece I want to get going is the 1 PPS
> interface, to provide the signal out, and to run the clock. In the
> manual it says the 1PPS signals are on the DB-25 connector, in
> differential "pseudo-ECL" form, but that's all - no level or common-mode
> info is provided. Online searching the term seems to indicate it's just
> PECL - Positive ECL running from +5 V, with everything shifted up
> accordingly. That's just fine (and easy to implement), as long as I know
> what to expect. I figured I'd check here to see if that's correct, or if
> it means something else in the Z3801A context. I'll find out eventually
> when I start fooling with it, but right now it's buried deep in the guts
> of the box, so not easy to scope out yet until I start hooking it up and
> designing the interface.

<snip long thread>