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X25AM Programming Manual

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ITI Applications
X25AM Programming Manual—527201-001
2-10
PAD Parameters
ITI issues three kinds of control packets. They perform the following tasks:
When the application clears a call as a result of issuing a CONTROL 12, ITI sends an
Invitation To Clear to the PAD. Any operations that are in progress (such as a data
transfer) are allowed to complete normally. The call is cleared by the remote device.
When a call is cleared with CLOSE, ITI sends a Clear to the PAD. Any operations in
progress are aborted.
PAD Response Packets
The PAD issues three kinds of response packets that are recognized by ITI. They
perform the following tasks:
•
BREAK. The terminal operator has pressed the BREAK key.
•
ERROR. Something was wrong with a PAD message. Clear the call.
•
READ. Response of the PAD parameter value.
Any other response packet type is discarded and ignored by ITI.
PAD Parameters
Both the PAD and the application must define the terminal that they are accessing with
the same operating characteristics (for example, 80 characters per line). PAD
operation is based on Recommendation X.3 that specifies the parameters that
describe these operating characteristics.
These parameters are set to a standard configuration each time a virtual call (SVC) is
established. Regardless of whether the call is initiated or accepted by ITI, ITI sends a
SET command to the PAD. This initial PAD configuration can be specified by the
operator with SCF or can be a default configuration that depends on the SCF
subdevice attribute REMOTENET.
Default parameter sets have an internal and an external format. ITI constructs the
internal format. ITI also translates the internal format to the external format. The
external format is the one sent to the PAD.
You can modify the parameter values programmatically with the DSM SPI program or
interactively with SCF.
Some file-system procedures can cause ITI to send SET PAD PARAMETER
commands that alter only a specific parameter. SETMODE 20, for example, which
•
SET Set PAD configuration parameters.
•
READ Read PAD.
•
INVITATION TO CLEAR Request PAD to initiate a Clear Call when the PAD has
finished all operations.
Note. If you choose to specify some PAD parameters, you must specify all standard and
network-specific parameters (not just those being modified).