Cables
Selecting a cable for the RS-232C interface is dependent on your specific
application. The following paragraphs describe which
lines
of the
HP 1650B/SlB are used to control the operation of the RS-232C relative
to the HP
1650B/51B.
To locate the proper cable for your application,
refer to the reference manual for your controller. This manual should
address the exact method your controller uses to operate over the
RS-232C bus.
Minimum
With a three-wire interface, the software (as compared to interface
Three-Wire
Interface with
Software
hardware) controls the data flow between the HP 1650B/51B and the
controller. This provides a much simpler connection between devices
since you can ignore hardware handshake requirements. The
HP 1650B/51B uses the following connections on its RS-232C interface for
Protocol
three-wire communication:
l
Pin 7 SGND (Signal Ground)
l
Pin 2 TD (Transmit Data from HP
1650B/51B)
l Pin 3 RD (Receive Data into HP
1650B/51B)
The TD (Transmit Data) line from the HP 1650B/51B must connect to the
RD (Receive Data)
line
on the controller. Likewise, the RD
line
from the
HP
1650BElB
must connect to the TD
Iine
on the controller. Internal
pull-up resistors in the HP
1650B/5lB
assure the DCD, DSR, and CTS
lines remain high when you are using a three-wire interface.
,I$
The three-wire interface provides no hardware means to control data flow
Note
d
between the controller and the HP
1650B/51B.
XON/OFP
protocol is the
only means to control this data flow.
Programming Over
RS232C
3-2
HP 1650B/HP 16518
Programming Reference
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