Asynchronous Terminals and Printer Processes Programming Manual

PROCEDURE CALLS FOR ACCESSING TERMINALS
Mode Switching
S5073-004
Application I/O Process LIU Device
SETMODE
(Page)
WRITE
(Screen)
SETMODE
Completion
SETMODE
(For Switch to
Page Mode)
WRITE
WRITE
Completion
WRITE
(EOT)
WRITE
(SOH, B, ETX, A)
SETMODE
Completion
Line Task
Writes Screen
WRITE
Completion
ACK
Figure 3-4. Mode Switching Example
The I/O process handles the SETMODE immediately by updating
its configuration area for the terminal. Thus, the application
request is completed right away. The application's WRITE request
causes two requests to be issued to the protocol module: one
SETMODE and one WRITE.
Pseudopolling
For pseudopolled terminals, if a nonzero PPOLL character is
specified, the protocol module issues the trigger character
automatically when performing a READ for the application. After
the terminal prompt character is received, the trigger character
is sent to the terminal to poll it for its data. Figure 3-5
illustrates pseudopolling.
3-12 November 1987