Asynchronous Serial Communications Programmer's Reference Manual (32022-90052)

224 Chapter8
Intrinsics Reference
FDEVICECONTROL
This directive will suppress the form feed normally sent
by the serial printer driver during close processing.
This FDEVICECONTROL is often used when an
application sends its own form feed at the end of a
document. The combination of the application’s form
feed and the serial printer driver’s form feed produces
an extra blank page at the end of the document. The
use of this FDEVICECONTROL will suppress the
serial printer driver’s form feed. This
FDEVICECONTROL must be called for every
document since it is automatically turned off at the end
of printing.
The buffer parameter is not used in this
FDEVICECONTROL.
This call is not supported for use with DTC Telnet,
Telnet/iX or VT. The driver will return a condition code
even though no device control action will take place.
76 Host and Device XON/XOFF enable.
This directive enables and disables XON/XOFF flow
control between device and the DTC.
Device XON/XOFF:
When device XON/XOFF is enabled, the DTC stops
sending data to the device when it receives XOFF. It
resumes it on receiving an XON. However, when the
XON/XOFF is disabled, the XON and XOFF characters
received by the DTC are simply passed to the host
without any interpretation.
Host XON/XOFF:
When Host XON/XOFF is enabled, the DTC sends an
XOFF character to the device when its receive buffer
becomes full. Then, when the data is transmitted to the
CPU, the DTC sends an XON character to the device
and restarts the input data flow.
There are four possible flow control settings for buffer
values:
0 disable both device and host flow
control
5 enable device flow control
9 enable host flow control
13 enable both device and host flow control