[time-nuts] Lucent KS-24361, HP/Symmetricom Z3809A, Z3810A, Z3811A, Z3812...
Bob Camp
kb8tq at n1k.org
Wed Nov 5 20:28:32 EST 2014
Hi
A little more snooping and U18 pops out. It’s an Atmel AT28C64B. Since it is a 64K bit EEPROM, that’s a much more likely place to stuff config items than redoing a flash chip. 64K seems pretty big for simple config variables and it’s a parallel EEPROM rather than a serial part. They may actually have code in there. When I originally looked at the board I assumed it was there to load the FPGA. If that’s what it’s for, the location is a bit odd. U2 seems like a more likely location for the load memory for the FPGA.I would also think that the FPGA memory would come pre-loaded.
Bob
> On Nov 5, 2014, at 8:01 AM, GandalfG8--- via time-nuts <time-nuts at febo.com> wrote:
>
> Hi Bob,
>
> Thanks for the information, I've still just been working from the J8
> Diagnostic port and it's about time I took a look at the RS422 output.
>
> The "proper" Ref-1 seems to be working as I'd expect, it's accepting a
> valid Ref-0 is present and going into standby as a result. Pulling out the
> link cable results in the Standby flashing and inserting the faker plug at
> this stage switches it straight to "ON", standby light now off, and enables
> the outputs.
>
> Unfortunately, persuading the other other Ref-1 that it's really a Ref-0
> would seem to involve a little bit more than the minor surgery I've
> performed so far:-)
>
> Regards
>
> Nigel
> GM8PZR
>
>
> In a message dated 05/11/2014 12:41:42 GMT Standard Time, kb8tq at n1k.org
> writes:
>
> Hi
>
> On a “real” Ref-0 / Ref-1 combo, the Lucent status message (RS-422 / PPS
> port) shows which device the string is coming from. This is independent of
> their status bits. Previous digging into similar units shows the same thing
> on earlier Lucent GPSDO’s. All the details are buried (200 posts back
> according to some ..) in one of my previous posts.I do not have anything on the
> diag port, so I don’t know what it says.
>
> Looking at the few unknown pins / pairs on the 15 pin connector, I’m
> guessing that one of them might be high or low depending on it being a Ref-0 or
> Ref-1. I’m also guessing that the pair on pin 15 is serial both ways. At
> this point my guessing average is not to good on these parts. I’m not really
> expecting that it will improve. Figuring out what the last few pairs do
> would be a nice thing.
>
> Bob
>
>> On Nov 5, 2014, at 7:20 AM, GandalfG8--- via time-nuts
> <time-nuts at febo.com> wrote:
>>
>> For what it's worth, here's what happened when I linked two Ref-1 units
>> together....
>>
>> One was fitted with it's GPS module as normal, I'll call this Ref-1.
>> The other was as normal other than having it's GPS module removed, I'll
>> call this Ref-1-0.
>> The link cable was around 15 inches long and wired 1-15, 2-14, etc,
> using
>> standard 15 way high density plugs.
>>
>> BTW, whereas shortened pins have been used in the past to ensure safe
> power
>> up sequences I'm pretty sure that on the Z3809A cable it's perhaps a
>> precaution to reduce the risk of bringing down the base station when hot
>
>> swapping.
>> I've noticed that removing my "faker" plug once a stand alone Ref-1 is
> up
>> and running starts to flash the Standby light but doesn't otherwise
> inhibit
>> operation, the 15MHz and 1PPS outputs remain available. I don't know how
>> long this might continue but the system obviously responds differently
> once
>> fully booted to when it's first powered and I suspect the use of
> shortened
>> pins could be related.
>>
>> Anyway, back to the two linked....
>>
>> At power up both go through the flashing light sequence, then...
>> Ref-1-0 -- "No GPS" - Flashing, "Fault" - Solid
>> Ref-1 ------"No GPS" - Solid, "Fault" - Solid
>>
>> After the boot period finishes.....
>>
>> Ref-1-0 -- "No GPS" - Flashing, "Fault" - Solid
>> Ref-1 ------"Standby" - Solid, all other lights off.
>>
>> Both units will talk via the J8 diagnostics port as soon as powered up
> but
>> Ref-1-0 behaves just as one would expect if the GPS module is removed,
> and
>> it doesn't seem to be relaying any data from the Ref-1 unit, whilst
> Ref-1
>> shows what looks to be a normal acquisition sequence, the onset of
>> conditioning, and a self survey
>> At no time is there a 15MHz or 1PPS output available from either unit.
>>
>> Although it's been conjectured that the firmware is identical in the
> Z3811A
>> and Z3812A, and the Prom markings certainly seem to confirm this, it
> would
>> also seem that there must be something that tells the unit what it is,
>> either by a firmware difference somewhere after all or perhaps a link
> on the
>> board somewhere.
>> This isn't just based on my not very successful experiment, although the
>
>> results are no great surprise:-), but my Ref-1 units always report
>> themselves to monitoring software as a "Z3811A Secondary Receiver".
>> Based on this am I correct in thinking that a standard Ref-0 would
> report
>> as a "Z3812A Primary Receiver"?
>> If so it has to get this information from somewhere.
>>
>> Regards
>>
>> Nigel
>> GM8PZR
>>
>>
>>
>> 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
>> unit.
>>
>> 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
>> board.
>>
>> 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.
>>
>> Cheers!
>> --Stu
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