7 Digital Communications Interface
Remote communications allowsan external device, such as a computer, to com-
municatewith the 1504 to obtain measurement data and control its operation.
Communication is accomplished with variouscommands issued to the 1504
through the RS-232 port or optional IEEE-488 port. A full list of commands is
givenin Section7.3.

7.1 Serial Interface

The 1504 isequipped with an RS-232 serial port. The RS-232 interface is use-
ful for connectingthe 1504 to most any microcomputer. The RS-232 socket is
located on the back panel of the 1504. Wiringof the interface cable should be
as shownin Figure 6 below. To eliminate noise, the serial cable should be
shielded with low resistance be-
tween the connector (DB-9) and
the shield.The protocol for
RS-232 communicationsis 8
data bits, 1 stop bit, and no par-
ity.The RS-232 interface uses
RTSand CTS for flow control.

7.1.1 Setting the Baud Rate

The 1504 must be set to the
same baud rate as the remote
device.The baud rate of the
1504 can be setto 1200, 2400,
4800, or 9600. The defaultis
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 displaythe current baud
rate. Use the Uand Dbuttons
to increase or decrease the baud
rate then press Enter.The next
parameter in theComm menu,
the serial sample period, will
then appear.
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7 Digital Communications Interface
Serial Interface
Figure6 Serial Cable Wiring