Page 37 of 133
Version 3.0 REV r000
Date 25-08-2010
5.1.3 Serial Communication
All serial interfacing is standard RS-232 protocol.
Pin Data
2 Receive
3 Transmit
5 Ground
Table 7: DB-9M RS-232 Standard Protocol
Pin Data Function
1 Receive2 Secondary Serial Port
2 Receive Primary Serial Input
3 Transmit Primary Serial Output
4 +12VDC +12VDC Power
5 Ground Data and Power Common
6 N/C Not Connected
7 +12VDC +12VDC Power
8 N/C Not Connected
9 Transmit2 Secondary Serial Output
Table 8: SIM DB-9M Serial pin assignment
5.1.4 Time and PPS input
5.1.4.1 Connecting PPS and Time to the SIM
In order to provide the most accurate multibeam data possible, the Sonic 2024/2022 takes in the
GPS Pulse Per Second (PPS) and NMEA ZDA time message or an ASCII UTC message, which is
associated with the pulse, to accurately time stamp the Sonic 2024/2022 data. The data collection
software will take in the same PPS and time message to synchronise the computer clock and the
auxiliary sensor data.
The PPS is normally a TTL (transistor – transistor logic) pulse. The pulse is transmitted to the SIM
and the data collection computer via a coaxial cable (such as RG-58); the cable is terminated with
BNC connectors so that it is easy to use a ‘T’ adaptor to parallel the PPS to different locations.
Connect one end of the coaxial cable to the GPS receiver’s PPS output (via a ‘T’ adaptor, if required)
and the other end to the SIM BNC labelled PPS. When a pulse is received, the light next to the BNC
connector will blink at 1 Hz.
The standard time message is a NMEA sentence identified as $GPZDA. The time message must go to
both the SIM and the data collection computer, so the message must be either split or output on
two different RS-232 ports on the GPS receiver.
5.1.4.2 Trimble UTC: UTC yy.mm.dd hh:mm:ss ab<CR><LF>"
Trimble GPS receivers provide the PPS time synchronisation message with an ASCII UTC string and
not the ZDA string. When interfacing a Trimble GPS, use the UTC message and not the ZDA for
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