Meinberg GPS167BGT, Operating Instructions Manual

Page: 52 / 62

52
Selection of Generated Time Code
The time code to be generated can be selected by Menu Setup IRIG Settings or the
GPS Monitorprogram. DC-Level Shift Codes (PWM signal) B00x and modulated
sine wave carrier B12x are always generated simultaneously. Both signals are provi-
ded at the VG64-Connector, i.e. if code B132 is selected also code B002 is available.
This applies for the codes AFNOR NFS 87-500 and IEEE1344 as well.
The TFOM field in IEEE1344 code is set dependent on the 'already sync'ed' character
('#') which is sent in the serial time telegram. This character is set, whenever the
preconnected clock was not able to synchronize after power up reset. The 'time figure
of merit' (TFOM) field is set as follows.
Clock synchronized once after power up : TFOM = 0000
Clock not synchronized after power up : TFOM = 1111
For testing purposes the output of TFOM in IEEE1344 mode can be disabled. The
segment is then set to all zeros.
Outputs
The module GPS167-TC provides modulated and unmodulated (DC-Level Shift)
outputs. The format of the timecodes is illustrated "IRIG-" and "AFNOR standardfor-
mat".
AM Sine Wave Output
The amplitude-modulated carrier is available at the VG connector pin 14a. The carrier
frequency depends on the code and has a value of 1 kHz (IRIG-B). The signal
amplitude is 3V
pp
(MARK) and 1V
pp
(SPACE) into 50
Ω
. The encoding is made by
the number of MARK amplitudes during ten carrier waves. The following agreements
are valid:
a) binary "0" : 2 MARK amplitudes, 8 SPACE amplitudes
b) binary "1" : 5 MARK amplitudes, 5 SPACE amplitudes
c) position-identifier : 8 MARK amplitudes, 2 SPACE amplitudes
PWM DC Outputs
The pulse width modulated DC signals labeled "IRIG" and "AFNOR standard format"
are coexistent to the modulated output and is available at the VG connector pin 13a
with TTL level.