AM3270/TR3271 Reference Manual

Level 4 Protocols
Overview of AM3270 and TR3271
2–4 086705 Tandem Computers Incorporated
CRT Protocol This is the basic mode of operation for 3270 terminals and printers. When a terminal is
configured in this mode, AM3270 adds the communication control characters on
output of the message and strips communication control characters on input.
The application program is totally responsible for the actual screen format control
(such as field protection or highlighting).
A 3270 terminal controller may send input data in 256-byte blocks. AM3270 gathers
the blocks together and passes a single buffer to the application.
PRT Protocol The PRT protocol provides line-at-a-time output to 3270-family printers from Tandem
program subsystems or user application programs. Each successive WRITE sent to a
subdevice that is configured in the PRT protocol results in the printing of a single line
on the subdevice.
QUO Protocol The QUO protocol provides support for Quotron devices. This protocol is used only
in those environments that have devices attached to a Quotron controller concentrator.
The controller concentrator multiplexes the messages that flow from many Quotron
devices through one logical AM3270 subdevice defined in the AM3270 I/O process.
Quotron devices are defined, monitored, and controlled through the SCF ADD SU and
SCF ALTER SU commands. CMI can not be used with Quotron devices.