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7 Digital Communications Interface
Remote communications allows an external device, such as a computer, to com
-
municate with the 1502A to obtain measurement data and control its operation.
Communication is accomplished with various commands issued to the 1502A
through the RS-232 port or optional IEEE-488 port. A full list of commands is
giveninSection7.3.
7.1 Serial Interface
The 1502A is equipped with an RS-232 serial port. The RS-232 interface is
useful for connecting the 1502A to most any microcomputer. The RS-232
socket is located on the back panel of the 1502A. Wiring of the interface cable
should be as shown in Figure 5 below. To eliminate noise, the serial cable
should be shielded with low re
-
sistance between the connector
(DB-9) and the shield. The pro-
tocol for RS-232 communica-
tions is 8 data bits, 1 stop bit,
and no parity. The RS-232 inter-
face uses RTS and CTS for flow
control.
7.1.1 Setting the Baud Rate
The 1502A must be set to the
same baud rate as the remote
device. The baud rate of the
1502A can be set to 1200, 2400,
4800, or 9600. The default is
2400. The baud rate is set in the
Comm menu. Press the Menu
button (“SEt?” appears) then
press the K/Comm button. The
display will briefly indicate
“SErIAL”, then “bAUd”and
then display the current baud
rate. Use the U and D buttons
to increase or decrease the baud
rate then press Enter. The next
parameter in the Comm menu,
the serial sample period, will
then appear.
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7 Digital Communications Interface
Serial Interface
Figure 5 Serial Cable Wiring