From: "Poul-Henning Kamp" <[EMAIL PROTECTED]> Subject: Re: [time-nuts] Off the wall: anyone with experienceprogrammingHP3456A? Date: Sat, 10 Sep 2005 23:16:59 +0200 Message-ID: <[EMAIL PROTECTED]>
> In message <[EMAIL PROTECTED]>, Magnus Danielson writes: > > >Just look in the HP5370B service manual and you see that the GPIB interface > >is > >"passive" (i.e. TTL chips rather than LSI chip). It may not be the marvel of > >modernism. > > Some of the smaller devices, like the VHF switches, the entire GPIB interface > is TTL and all commands are single byte commands... Which surely makes things *MUCH* simpler. > btw: the reason for the limit on number of devices powered down is > that NMOS/TTL based interface chips tend to clamp the bus to ground. Which should be compared to the relative strong pull of 48 mA. Some implementations is not strong enought. > This is less of a problem with modern CMOS based interface chips. Actually, there you end up in another problem, you power the box through the protection diodes which you really must have for CMOS. So it is really not so much better, just different. Cheers, Magnus _______________________________________________ time-nuts mailing list time-nuts@febo.com https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
