8 Communications Interface
Remote communications allows an external device, such as a computer, to com
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municate with the 1521 to obtain measurement data and control its operation.
Communication is accomplished with various commands issued to the 1521
through the RS-232 serial port.
8.1 RS-232 Connection
The three-conductor jack for the serial port is located on the top of the 1521
near the probe connector. One serial cable is included with the 1521. Additional
or longer cables, of three meters or less, can be constructed by following the
wiring diagram shown in Figure 8. Note: The TxD line on one side connects
to the RxD line on the other and vice-versa. To reduce the possibility of elec
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trical interference, the serial cable should be shielded with low resistance be
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tween the connector and the shield. It should not be much longer than is
necessary. The protocol for serial communications is 8 data bits, 1 stop bit, and
no parity. Use no flow control. The baud rate is fixed at 2400, the linefeed to
37
8 Communications Interface
RS-232 Connection
1
2
3
4
5
6
7
8
9
RxD
TxD
GND
RxD
TxD
GND
Figure 8 RS-232 Wiring
