[time-nuts] Lucent KS-24361, HP/Symmetricom Z3809A, Z3810A, Z3811A, Z3812A GPSDO system
brooke at pacific.net
Tue Nov 4 12:26:52 EST 2014
VP CMC2003 M12 GT+ UT+
Description PC Cmd Cmd Rply PC Cmd Cmd Rply PC Cmd Cmd Rply PC Cmd Cmd Rply PC Cmd Cmd Rply
Position-Status-Data Out Message ps8 Ea Ea ps12 Ha Ha ps12 Ha Ha ps8 Ea Ea ps8 Ea Ea
UARTs are not mandatory, a simple transistor level shifting circuit is all that's needed for TTL/RS-232 levels.
Once I receive the Ref-0 and Ref-1 boxes and cable I'll start filling in my web page:
Brooke Clarke. N6GCE
Stewart Cobb wrote:
> A wiring diagram of the Z3809A cable interconnect cable was published
> earlier on this list. That information appears to be incorrect. The
> cable is actually wired pin 1 to pin 15, pin 2 to pin 14, etc.
> Another way to describe it is that for each wire in the cable, the pin
> numbers on each end of the cable add up to 16.
> A mated pair of these units is running in my lab with a scratch-built
> interconnect cable following the above rules. This scratch-built
> cable allowed access to the interconnect signals while the system was
> operating happily. No lights were lit except the green ON light on
> the Ref-0 unit (Z3812A, no GPS) and the yellow STBY light on the Ref-1
> unit (Z3911A with GPS receiver). The following signals were observed
> on the interconnect (pin numbers given for the J5 interconnect socket
> on the Ref-1 unit):
> Pin 1: 9600 baud serial data (described below)
> Pin 2: logic low (0.11V)
> Pin 3: Ground (0.00V) Presence detect? (see below)
> Pin 4: logic high (4.79V)
> Pin 5: inverted Motorola PPS, high (5V) for 800ms, low for 200ms
> Pin 6: "17 / 23 dBm" signal from Ref-0 unit (see below)
> Pin 7: logic high (4.48V)
> Pin 8: Ground (0.00V)
> Pin 9: logic low (0.11V)
> Pin 10: "17 / 23 dBm" signal from Ref-1 unit (see below)
> Pin 11: inverted PPS, low 400us, high (5V) otherwise
> Pin 12: logic low (0.12V)
> Pin 13: Ground (0.00V)
> Pin 14: logic low (0.08V)
> Pin 15: logic high (4.78V)
> Pins 3, 8, and 13 appear to be firmly connected to Ground. (Note that
> these are the three pins which are clipped short on the HP
> interconnect cable.) On an unpowered, disconnected box (either Ref-0
> or Ref-1), pins 8 and 13 are connected to Ground (low resistance) and
> pin 3 is high impedance. Presumably pin 3 on each box (connected to
> the grounded pin 13 on the other box) is used to sense the presence of
> the other box and/or the interconnect cable.
> The timing of the PPS signal on pin 11 matches precisely the timing of
> the PPS signal available on pins 1 and 6 of J6 (RS422/PPS) on the
> active Ref-0 unit. Presumably this signal is coming across the cable
> from the Ref-0 unit.
> Note: when the system is coming up from a cold start, SatStat on the
> unit with the GPS receiver (Ref-1) will show "[Ext 1PPS valid]" in the
> space where it shows "[GPS 1PPS valid]" after the survey is complete.
> It appears that the Ref-1 unit timing system is locking its oscillator
> to the PPS coming from the Ref-0 unit during this time.
> The timing of the PPS signal on pin 5 matches the timing of the PPS
> output described in the Motorola OnCore manual. Presumably this
> signal is sourced by the Ref-1 unit to allow the Ref-0 unit to lock to
> GPS. The edges of this PPS signal look very dirty compared to the
> signal on pin 11. This may be an artifact of the homemade cable used
> for this experiment. The HP cable clearly has an overall shield
> (visible through the cable sheath) and may have internal coax or
> twisted pair for these PPS signals.
> When pin 5 and pin 11 are observed together, the usual GPS sawtooth
> pattern is evident.
> Someone discovered earlier that the both units will blink their green
> ON lights if the front-panel switch on either unit is set to 23 dBm
> vice the normal 17. Obviously each unit can communicate its switch
> status to the other unit. They use pins 6 and 10 to do that. Pin 10
> (on the Ref-1 unit) is high (~5V) if the switch on the Ref-1 unit is
> in the 17 dBm position, and low in the 23 dBm position. Pin 6 (on the
> Ref-1 unit) gives the same indications for the switch on the Ref-0
> The serial data on pin 1 is transmitted at 9600 baud, with a burst of
> data every second. The signal idles at logic low (near 0V) and rises
> to logic high (near 5V) during the burst. This may be the standard
> for TTL (not RS-232) transmission of serial data, or it may be
> inverted. The first few characters of one burst were hand-decoded
> from a scope trace as 0x40, 0x40, 0x45, 0x61, 0x0B, or ASCII "@@Ea".
> This appears to be the Motorola Oncore binary data format, although
> "Ea" does not appear to be a valid Motorola command or response.
> Perhaps the hand-decoding was in error.
> One can use SatStat, talking to the Ref-0 (non-GPS) box, to issue
> queries and commands to the GPS receiver. The results are
> inconsistent, but it seems that at least some of the queries get
> through and trigger responses. If the Ref-0 box is actually talking
> to the GPS receiver, it must be doing so through the interconnect
> cable. The specific wire in the cable used for this (if any) has not
> yet been identified.
> An earlier post speculated that the computer in each unit only had two
> UARTs. This does not seem possible. Clearly each unit uses one UART
> to communicate with the J8 diagnostic port. The Ref-1 unit needs
> another UART to communicate with the GPS receiver. And both units need
> to be able to transmit the legacy Lucent timecode message out the J6
> (RS422/1PPS) port. Perhaps there is a transmit-only UART coded into
> the FPGA, or perhaps one of the UARTs is timeshared with the Lucent
> message, or perhaps there is another UART chip hidden somewhere on the
> It seems unlikely that the two units are sending serial data to each
> other. (No such data was observed on the interconnect.) Instead,
> they appear to communicate their state to each other by means of logic
> levels on various pins of the cable. The logic functions of pins 6
> and 10 have already been identified. Further research is needed.
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