> The designers very well designed two near inifinite counter chains inside the > 5335A.. > I got my wisdom from the hp journal 9-1980.
http://www.hpl.hp.com/hpjournal/pdfs/IssuePDFs/1980-09.pdf > They used a digital ASIC, called the MRC, multi-register counter, and it > allows counting > of the input signal and the time base, each 20 decades long. (see page 26). Just to be clear, the MRC itself has only 8 decades. You get additional decades with off-chip processing, which is to say, counting overflows. It's the same way we keep 64-bit time in a microcontroller: 16 bits of timer and then 48 more bits of overflow count. "Another feature of the MRC lets its internal eight-decade count chains be expanded to any number of decades with the help of a processor. This feature is used to create a pair of count chains, each 20 decades long. With a 100-MHz signal, this chain would take more than 30,000 years to overflow. Consequently, the 5335A has no overflow annunciator, so gate times can be as short as 0 ns or as long as years." There's more good info on the MRC starting on page 12 of an earlier HP journal: "A High-Performance Bipolar LSI Counter Chip Using EFL and I2L circuits" http://www.hpl.hp.com/hpjournal/pdfs/IssuePDFs/1979-01.pdf The heritage of the MRC shows up in my picPET (Precision Event Timer). Notice how hp's MRC also has an E-register (Event) and a T-register (Time). Once you have matched {event count, time stamp} pairs anything is possible. By "anything" I mean, totalizing, absolute time, time interval, frequency, period, mean frequency, period average, best fit frequency, sigma, sigma(tau), ADEV, etc. BTW, if any hp old-timers reading this posting happen to have detailed information on the 40-year old proprietary MRC chip, please contact me off-list before it's too late. By too late I mean: http://www.pressdemocrat.com/business/7559762-181/hewlett-packard-archives-at-keysight-destroyed /tvb _______________________________________________ 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.
