[time-nuts] Lucent KS-24361, HP/Symmetricom Z3809A, Z3810A, Z3811A, Z3812A GPSDO system
goetz at g-romahn.de
Tue Nov 4 12:11:06 EST 2014
J5 (interconnect) pins are routed to the kathode of smd-ics labeled
Z2upperindex3. These look like z-diodes to protect further circuitry
The following pins are routed this way: 1,2,3,4,9,10,11,12,14,15
Am 04.11.2014 13:43, :
> Ok so the correct pairs should be:
> A 1 15
> B 2 14
> C 3 13
> D 4 12
> E 5 11
> F 6 10
> G 7 11
> ground 8 8
>> On Nov 4, 2014, at 4:38 AM, Stewart Cobb <stewart.cobb at gmail.com> 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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