The 8170 isn't smart enough to calculate the leapsecond immediately. Instead, it uses its error correction routine which takes about 4 minutes after the event to realize that it is one second off, then updates the time to match. Details quite far down the page at http://www.febo.com/pages/leapsecond_2005/ John ---- On 2/22/2012 2:48 PM, Jim Hickstein wrote: > On 2012/01/23 15:28, Jim Hickstein wrote: >> Reviewing the schematic for the 8170 (I'll get back to the setting >> coil in the >> clock a bit later), my unit does not seem to have Option 18 and A4-U4, >> the 8255A >> at its heart, is not populated. A pity: it would have lovely BCD >> outputs and an >> on-time pulse, just what I need. (The recent discussion of multiplexed >> 7-segment >> LED outputs tells me I don't want to try to detect ":00:00" or >> ":59:59" there.) >> >> What are the chances my EEPROMs would DTRT if I just added an 8255A to >> this >> board? > > Looking better today. I dragged a scope up from the basement. CS is > getting hit, about 11 times, near the beginning of each second (image). > I guess this means I have to design the circuit, now, and place an order > for some parts. > > > What other components should I add to complete the Option 18 > installation? > > A3U4, the 8255A, seems to be the only thing missing, apart from A3J4, > the 50-pin header that connects to a cable to bring these BCD signals > out to the rear panel DD-50, also missing. For my purposes I can stop at > the header. It'll be a nice place to mount a little daughterboard. This > is on sheet 4 of A3, the uP board schematic, not on a separate sheet as > some other options are. > >> If I need different EEPROMs to enable Option 18, where could I get the >> image? >> (The parts and the programmer I can probably get.) > > Perhaps I'll do a socket and the 8255A first, just to see the output > pins move as expected. This means paying Digikey for shipping twice. Oh, > well. (Anyone near http://www.airnav.com/airport/KMSP got an 8255A lying > around? I have some Augat 40-pin sockets left over from 1983, packrat > that I am.) > > Maybe I can get it done in time to have it send a pulse to the clock > during :59:59 _or_ :59:60. :-) I don't recall if an 8170 is quite that > savvy, to produce this on its output, but the BCD encoding could do it. > We'll find out, eh? And the clock will be set properly the next hour, > anyway. > >> >> On 2012/01/20 16:23, Jim Hickstein wrote: >>> I have a Spectracom 8170 in the living room (who doesn't?), and a >>> Western Union >>> time-service clock, a.k.a SWCC clock -- a nice one, in a 3-foot-high >>> wood case. >>> I've been watching TV with this combination for years and years but >>> never got >>> around to feeding a pulse from the 8170 to discipline the other one. >>> Now that >>> Western Union no longer provides the service. :-) But it just begs to >>> be done. >>> >>> I did draw up a TTL circuit, once (on a napkin, naturally, which I >>> have now >>> misplaced), that could live inside the 8170. I figured out the >>> minimum number of >>> inputs needed to detect when the MM:SS LED displays said 00:00 (for >>> one second). >>> It would close a relay, which could feed the winding-battery power to >>> the >>> hour-set solenoid down a pair of wires from 10 feet away. But I never >>> built it. >>> >>> A little over a year ago the TS clock was getting gummy and >>> free-running slower >>> and slower, so I sent it to the clock hospital. It's back and >>> free-running >>> nicely, so maybe it's finally time I did this. Anyone got a better >>> idea than my >>> little TTL circuit, on a breadboard inside the 8170? I'd like to get >>> it across >>> the rear panel without cutting a new hole, if I can avoid it. But >>> maybe the >>> right connector would do. Another time-code receiver in the TS clock, >>> e.g. a GPS >>> module that provides a relay closure for 1 second on the hour (if >>> such exists) >>> might be neater. But the living room faces north. >>> >>> _______________________________________________ >>> time-nuts mailing list -- time-nuts@febo.com >>> To unsubscribe, go to >>> https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts >>> and follow the instructions there. >> >> >> _______________________________________________ >> time-nuts mailing list -- time-nuts@febo.com >> To unsubscribe, go to >> https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts >> and follow the instructions there. > > > > _______________________________________________ > time-nuts mailing list -- time-nuts@febo.com > To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts > and follow the instructions there.

On 2012/02/22 13:48, Jim Hickstein wrote: >> What are the chances my EEPROMs would DTRT if I just added an 8255A to this >> board? They do. Socket and 8255A added, signals present on the 50-pin header as documented for Option 18, so I'm proceeding with my little TTL circuit to set the SWCC clock on the hour. (Contact me privately if you want criticize my schematic. I'd love to get some help with that, as I haven't done this kind of thing for decades. I'm an Extra, but not an EE.) This (image) is the 1PPS and seconds-LSB signal, over two seconds. Sorry for the focus. I could get out the better camera for this, I suppose. Digikey order arrived today. Whee!! Now I just have to see if I still remember which end of a 14-pin DIP is "up". (Joke! Some things you just cannot forget, even after decades.) Digikey had everything I needed except the 40-pin DIP package of the 8255A. But I easily found one on eBay. That makes it an antique. Copyright 1975.