X25AM Programming Manual

ITI Applications
X25AM Programming Manual—527201-001
2-16
Data Processing
Checking Block Size for Nonstandard Terminals
Nonstandard terminals that emulate HP terminals might have a nonstandard block
size. If your application program may access a nonstandard terminal, you may want to
check the block size setting. Block size is specified with the SYSGEN X25AM macro
modifier PAGE6520BLKSIZE (which has a default value of 256 bytes) or with the SCF
subdevice attribute PAGE6520BLKSIZE.
For details about the PAGE6520BLKSIZE modifier, refer to the X25AM Configuration
and Management Manual.
Data Processing
Aspects of processing data, other than its exchange between the application and the
terminal, that pertain to ITI include data forwarding, data packetizing, and control
character disposition. The following subsections describe these aspects.
Forwarding Data from the PAD
As the terminal transmits characters to the PAD, the PAD retains the characters until
certain conditions occur. Then the PAD packetizes and forwards the data. Data
forwarding occurs under the following conditions:
•
The PAD buffer is full.
•
The maximum time allotted for the interval between characters from the terminal
has passed.
•
Data-forwarding characters occur in the data stream.
•
A break signal is received from the terminal.
Forwarding Data and Data-Forwarding Characters
Data-forwarding characters occur in the data stream from terminals in conversation
mode. The data-forwarding characters that cause the PAD to packetize and forward
data are specified with PAD parameter 3. ITI uses only these two parameter values:
•
Parameter 3 value 2 (carriage return (CR))
•
Parameter 3 value 126 (any HEX character from 00 - 31 and DEL)
The parameter value that is sent to the PAD depends on the interrupt characters
specified for ITI. Interrupt characters indicate to ITI that something needs to be done
with the buffer that has been transmitted from the PAD (including the interrupt
character) and that some response to the terminal may be required.
Four interrupt characters are defined for any conversational terminal configuration.
Table 2-5 on page 2-17 lists the default values for these characters for a standard 6530
terminal.