Timewave DSP-232, Operating Manual

Page: 205 / 271

Chapter 11 SIAM and NAVTEX Operation
NAVTEX switches your DSP into the NAVTEX receive mode. The DSP can accept or reject certain message
classes and transmitting stations with the
NAVMSG
and
NAVSTN
commands.
For logging purposes,
NAVTEX uses the setting of DAYTIME to print the date and/or time in front of the preamble
if
MSTAMP
and
DAYSTAMP
are both
ON
.
Nums
Immediate Command
Mode: Baudot, AMTOR, TDM Host: NX
In Baudot, AMTOR and TDM receive, the
NUMS
command will force the DSP into the FIGS case.
OK
Immediate Command
Mode: SIGNAL Host: OK
OK normally follows the SIGNAL command after it has determined the class and speed of the station you’re
listening to. Typing OK will change the commands RXREV , RBAUD or ABAUD and OPMODE to their proper
value.
If the
SIGNAL
command doesn’t reveal any useful information, typing
OK
will produce the ?bad error message.
QSignal
Default: 1 (Modem 1)
Mode: Signal Host: QS
n
Modem number to be selected when the SIGNAL mode is entered.
QSIGNAL sets the DSP-232 modem that will automatically be selected when the SIGNAL Identification mode is
entered.
See the SIGNAL (this chapter) and MODEM (Chapter 4) commands for more infromation.
SAmple n Immediate Command
Mode: Command Host: SA
“n” 20 to 255 specifies the sampling rate in baud.
This operating mode is for advanced users interested in decoding unknown synchronous data transmissions.
SAMPLE
is similar to the
5BIT
and
6BIT
modes, but operates on synchronous data.
SAMPLE
syncs up on any regularly-paced data transmission and samples the data once per bit, packaging the data
in groups and sending the groups to the you for further analysis. You can use SAMPLE to capture data bits from
synchronous transmission modes such as FEC, TDM or an “unknown mode” not identified by the
SIGNAL
command. (The transmission is actually sampled several times per data bit.) The DSP does a majority vote on the
last few samples to represent the value of the data bit.
One use for the
SAMPLE command is to record the output to a disk file, then write a program to analyze the results
for synchronous/asynchronous, bit sync patterns, data decoding, etc.
SAMPLE
data is captured in 6-bit units; the order of bit reception is MSB first, LSB last. The TNC sends the data
unit to you with a constant of hex 30 added to each unit, the same as the 6BIT command. The 6-bit unit is a
compromise between hex and 8-bit binary output. The 6-bit unit yields shorter disk files than 4-bit hexadecimal
characters, but encounters no interference from terminal communications programs and the TNC’s Converse and
Command modes. The 6-bit unit’s range of $30-6F falls within the printable ASCII range, allowing the TNC to
insert end-of-line carriage returns that can be ignored by your analysis software.
11-6 September, 05