HA243821
Issue 5 Mar 98
Section5
Page 5 - 27
MODEL 346 INSTALLATION AND OPERATION MANUAL
5.7 COMMUNICATIONS OPTION
5.7.1 INTRODUCTION
The communications option allows a host computer to obtain (read) or change (write) most of the values and
operational states within the recorder. The exceptions are: a) that it is not possible to access the communications
parameters (eg. Baud rate), and b) the host is not able to calibrate the recorder.
5.7.2 INSTALLATION
The communications option consists of a communications circuit board (which may include event inputs, if re-
quired), terminal connectors and operating software. If the communications option is being retro-fitted, an
upgrade to the recorder software may also be necessary: please contact the local agent for details.The locations
of the communications connectors are shown in figure 5.7.2b below. If the communications board is fitted with
event input circuitry, then the connectors are also as shown below, otherwise, a blanking piece is fitted.
WIRING
The Tx- and Tx+ terminals of the recorder are connected to Tx- and Tx + of all the other recorders in the commu-
nications link, and to the Rx- and Rx+ connections, respectively, of the host computer. The Rx- and Rx+
terminals of the recorder are connected to Rx- and Rx+ of all other recorders in the communications link, and to
the Tx- and Tx+ connections, respectively, of the host. Figure 5.7.2a shows a simple wiring diagram with two
recorders. The following sections on biassing and terminating resistors give further details.
For computers with RS232 connections, an RS232 to RS422 conversion module is available from the manufac-
turer, stocked under the part number LA245282.
Figure 5.7.2a Link wiring
Tx-
Tx+
Rx+
Rx-
Tx-
Tx+
Rx+
Rx-
5V
0V
First 345/6
recorder
Final 345/6
recorder
470
Ω
470
Ω
220
Ω
Rx-
Rx+
Tx+
Tx-
Host
computer or
terminal