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

202 Chapter8
Intrinsics Reference
FCONTROL(41)
Subsystem break processing also occurs as in normal editing mode,
except that the subsystem break character is defined through the
FCONTROL(41) call.
Because DC1 and DC2 (if the DC2 is the first byte of data) are
recognized as special characters, transparent editing can be
successfully used during block mode reads.
NOTE When several files are open on a device at the same time (multiple
FOPEN calls were issued), transparent editing will be in effect for all of
the files if it was explicitly enabled for any one of them.
If you enable binary editing, transparent editing is automatically
overridden. When you leave binary mode, however, transparent mode
will still be enabled. Binary mode will only be enabled for the file on
which it is enabled. Other files will continue to operate in the mode,
normal or transparent, that was set before binary was enabled.
Parity processing is the same in transparent mode as in standard mode.
Standard editing is restored by calling FCONTROL(41) with the value
of param set to 0. Any FCLOSE call issued against the terminal will
also restore standard editing.
It is possible to enable transparent editing for devices connected via
PAD. However, since the PAD will still expect to see a
[Return] as the
data forwarding character, data will not be forwarded from the terminal
immediately after the characters defined as the subsystem break or
EOR characters are typed. The terminal user will need to press
[Return]
to cause data to be transmitted, or wait for the data forwarding timer to
expire if it has been set. The host software will still recognize and act on
the characters defined in param.
If this call is issued against a terminal connected via VT from an
MPE V or HP-UX local client, the subsystem break character may not
be redefined. Bits (0:8) should be the existing subsystem break
character to keep status unchanged or set to 0 to return to edited mode.
Condition Codes
CCE Request granted.
CCG Not returned by this intrinsic.
CCL Failed because the file number specified did not belong
to this process, the device is not a terminal, or an illegal
value was passed in param.