This use of the FCONTROL intrinsic stems from an
early point in the development of Hewlett-Packard operating systems
when it was necessary to allocate a terminal before it could be
opened programmatically. This is no longer necessary, but the intrinsic
is still in use today and allows you to programmatically set both
terminal type and speed for a terminal through a single call. Both
of these values can be set individually through other FCONTROL calls.
When you use FCONTROL(37), param passes
the desired speed and terminal type values. The speed is represented
in characters per second and is contained in bits (0:11). The terminal
type is contained in bits (11:5).
You must be sure the speed associated with a device matches
the physical speed setting of the device and of the modem, if a
modem is part of the device connection. If you programmatically
change the speed of a device your program should request that the
speed setting be manually changed at the device as well.
You cannot use FCONTROL(37) to set the terminal to an unsupported
speed or terminal type. Attempting to do so will cause an error
condition of CCL. You cannot use FCONTROL(37) with user-defined
terminal types. You must call FDEVICECONTROL to specify the terminal
type when using a terminal type defined through the Workstation
Configurator.
If issued against a terminal connected via PAD, DTC Telnet,
or Telnet/iX, this call will change the terminal type setting, but
will have no impact on how the device actually operates. A CCE condition
code will be returned.
This call is unsupported for devices connected via VT. If
used, the VT driver will return a CCE condition code, but no device
control action will take place.
