HANDSHAKE regulates
flow of control by specifying how and if a device can signal to the
host to temporarily halt transmission and then resume it. Flow control
is important because it is possible to send commands to a hard copy
device faster than they can be executed.
HANDSHAKE can be used
when you are using a protocol converter, interface program, or host
computer that can perform XONXOFF or hardware handshaking. You can
also use this option if you are routing output through flow-control
programs of your own, as in a multiple-machine personal computer environment
where the graphics plotter is a shared resource.
SAS/GRAPH software
sends output to a server (the file transfer does not require flow
control). The server queues incoming graphs and sends them to the
plotter. The server, rather than
SAS/GRAPH software, is responsible
for handling flow control. An interface program is usually invoked
by the line printer daemon and provides formatting or control signals
for a system destination. The interface program typically includes
port configuration options, such as baud, parity, and special character
processing requirements (raw or cooked mode) for that destination.
If you do not use HANDSHAKE,
the value in the driver entry is used.
If you use HANDSHAKE=XONXOFF
or HANDSHAKE=HARDWARE,
SAS/GRAPH does not actually do the handshaking.
It tells the device which type of handshake is being used. The protocol
converter, interface program, or host computer actually does the handshake.
Note: If you are creating a graphics
stream file using a driver for a plotter and you specify HANDSHAKE=SOFTWARE,
the software that you use to send the file to the plotter must be
able to perform a software handshake. You will probably want to specify
one of the alternative values if you route output to a file.