[time-nuts] Lucent KS-24361, HP/Symmetricom Z3809A, Z3810A, Z3811A, Z3812...

GandalfG8 at aol.com GandalfG8 at aol.com
Wed Nov 5 07:33:38 EST 2014

PS, re two Ref-1 units linked....

I forgot to mention that unlike Stewart's comment re a normal pair  below, 
my Ref-1 continues to show "GPS 1PPS Valid"

It would seem there's some of the handshaking working ok but not much  
actual activity being shared, will have a further poke about later.

In a message dated 04/11/2014 09:38:25 GMT Standard Time,  
stewart.cobb at gmail.com writes:
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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