X25AM Programming Manual

ITI Applications
X25AM Programming Manual—527201-001
2-3
The Remote Terminal and the Subdevice File
Refer to the Guardian Procedure Calls Reference Manual if you need more information
about these procedures.
The Remote Terminal and the Subdevice File
Communication with a remote terminal is accomplished by reading from and writing to
a subdevice named $line-name.#subdevice-name. Before any communication
with a remote terminal can take place, the application process must open the
subdevice.
The subdevice:
•
Must be configured for the ITI protocol attribute at the time that it is opened.
•
Must be configured for the terminal type being used.
The terminal type is initially set interactively with the Subsystem Control Facility (SCF)
or programmatically through the DSM SPI interface. All terminals are assumed to be in
conversation mode when the switched virtual call (SVC) is established. They can be
altered to page mode with the SETMODE 8 procedure. Page mode operation for 6510
type terminals differs slightly from page mode operation for 6520 and 6530 terminals.
Phases of a Connection
Call connection consists of the following phases: initiating a call, waiting for a call,
configuring PAD parameters, exchanging data, and clearing a call. The following
subsections describe the phases of call connection.
Initiating a Call
Your application initiates a call when it is necessary to start a data exchange with the
remote terminal. Initiating a call means a Call Request is sent and a network response
is received. Your application initiates a call with a CONTROL 17. The remote network
Note. If your application uses the CANCEL procedure to cancel a READ command, data can
be lost.
Table 2-2. Terminal Types Supported by ITI
Type, Subtype Terminal Mode
6,0 Conversation mode. Cannot be changed to page mode.
6,1 6510
6,2 6520
6,4 6530
Others Assumed to be type 6,0.
Note. These phases apply to switched virtual circuit (SVC) connections only.