The one you describe is the one I use with my 5313's, would be nice to see how they do it, they must inject the 60 and 600 Hz further up. I do not see how they can set the second digits at 60 Hz they would scroll awful fast. I use a 555 but at 3 Hz, 60 Hz and about 1 KHz. My counter counts down to 1 Hz but can be preset by Tbolt or a thumb wheel device and also has a hold function. That chip family is definitely intended for accurate 1 sec. clocks and combining dividing,synchronizing and setting is not trivial. A PIC could do it,but I do not have the skills. Bert In a message dated 9/28/2011 3:05:51 P.M. Eastern Daylight Time, [email protected] writes:
Yes Bert, the "three-board" type uses the counting scheme that you described, but the other type is as I described. On the "two-board" version the "set" mode is permanent, and there is no external counter or logic. The 555 is a normally a one-shot for stretching the narrow 1 PPS pulses from the Rb system, but oscillates at around 60 or 600 Hz (precision not important) during setting, accomplishing the same result. I think this design is the later one - someone at HP may have had a "eureka" moment and realized that this simpler approach could eliminate a board full of logic. Ed In a message dated 9/27/2011 9:10:25 P.M. Eastern Standard Time, <https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts>EWKehren at aol.com writes: Sorry Ed you are wrong. Hp generates a 65 Hz signal that advances the internal prescaler 49 counts and uses the 1 pps output to stop the 65 Hz output at count 49 and waits for the internal 1 pps to go to 50 and advance the second digit one count. Sounds crazy but it works, makes the clock advance in perfect sync with the internal second generator. Bert Kehren In a message dated 9/27/2011 8:16:43 P.M. Eastern Standard Time, <https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts>eb at telight.com writes: After looking at the manual, I realized that I did look at this series of parts way back, but didn't get the connection because I thought it would have to be a type that takes 1 Hz input rather than 50/60 Hz. I see now that they were used in the "set" mode, bypassing the internal divide by 50/60. The clock module I have is the type with a 555 used as a one-shot for normal operation, or as an oscillator for fast setting. I think this is probably the newer of the designs, since it is simpler. _______________________________________________ time-nuts mailing list -- [email protected] To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there. _______________________________________________ time-nuts mailing list -- [email protected] To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
