The RTS (Request To Send), is an output from the HP
1650BblB
which
can be used to control incoming data flow.
A
true on the RTS line allows
the controller to send data and a false on this
line
signals a request for the
controller to disable data transmission.
The CTS (Clear To Send), DSR (Data Set Ready), and DCD (Data
Carrier Detect)
lines
are inputs to the HP
1650BElB
which control data
flow from the HP 1650B/51B (Pin 2). Internal
pull-up
resistors in the HP
1650B/5lB
assure the DCD and DSR
lines
remain high when they are not
connected. If DCD or DSR are connected to the controller, the
controller must keep these
lines
and the CTS Iine high to enable the HP
1650B/5lB
to send data to the controller. A low on any one of these lines
will
disable the HP
1650B/5lB
data transmission. Dropping the CTS
Iine
low during data transmission
wiII
stop HP 1650B/51B data transmission
immediately. Dropping either the DSR or DCD
line
low during data
transmission will stop HP 1650B/51B data transmission, but as many as
two additional bytes may be transmitted from the HP 1650B/51B.
Cable Example
Figure 2-l is an example of how to connect the HP 1650B/51B to the
HP 98628A Interface card of an HP 9000 series 200/300 controller. For
more information on cabling, refer to the reference manual for your
specific controller.
II~’
Since this example does not have the correct connections for hardware
Note
4
handshake,
XON/XOFP
protocol must be used when connecting the
HP 1650B/51B as shown in figure 2-l
Programming
Over RS-232C
3-4
Figure 2-1. Cable Example
HP 1650B/HP 1651B
Programming Reference
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