Asynchronous Terminals and Printer Processes Programming Manual

TERMINAL I/O
Flow Control Characteristics
Transmit pause (TPAUSE) allows a buffered, RS-232 device to
delay transmission from the controller so the device can empty
its buffer. The device must raise its secondary received line
signal detector (SCF). The controller then delays transmission
until the device drops SCF. TPAUSE and CTS flow control cannot
be active at the same time. If both are enabled, CTS takes
precedence.
The RC SYSGEN modifier indicates the presence of a half-duplex,
reverse-channel, 202-type modem. This modem requires request to
send (RTS) to go low when switching from transmit to receive.
Secondary data carrier detect (SDCD) must be high to the DCE when
receiving. For ATP6100 subdevices, you can change the SYSGEN
default by including the REVERSECHN attribute in a CMI ALTER SU
command. The LIU4 does not support reverse channel modems.
The ETX1 and ETX2 SYSGEN modifiers specify the number of
characters (1 or 2) in the checksum that follows the end of text
(ETX) character. One or two checksum characters are returned
to the application and reflected in the count-read value. The
checksum must be calculated by the application. The absence of
both ETX1 and ETX2 indicates no checksum. You can change the
SYSGEN default with a SETMODE 13 procedure call. For ATP6100
subdevices, you can also change the default by including the
ETXENABLE attribute in a CMI ALTER SU command.
For ATP6100, the ETXCHARC SYSGEN modifier allows you to specify
a character to be used for termination of read operations. You
change the SYSGEN default by including the ETXCHAR attribute in
a CMI ALTER SU command. Also, for ATP6100 subdevices, the ETB
SYSGEN modifier specifies that read termination occurs on the end
of text block (ETB) character. ETX1 or ETX2 can also be selected
to allow a checksum after the ETB character.
Interrupt Characteristics
The 6100 CSS or T6303/4 controller can examine characters
received from the terminal and compare them to interrupt charac-
ters. If the received character equals one of the interrupt
characters, the controller generates an I/O interrupt. This
interrupt, invisible to the application process, notifies ATP6100
or TERMPROCESS that the controller has received an interrupt
character. ATP6100 or TERMPROCESS then takes appropriate action.
In some cases this means notifying the application process.
Table 2-6 lists the parameters that control interrupts.
November 1987 2-11