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Data Communications
BUFFER SIZE. You must set the amount of terminal memory allocated for use as input and
output communication buffers. When the terminal is inputting data it uses this space for input
buffers. When the terminal is outputting data the buffer space is divided into two or more
output buffers. The basic terminal configuration uses two 250 byte output buffers.
When the terminal is selected, any data waiting in the output buffers is lost. The output buffers
then become input buffers to hold data sent from the computer until the terminal can process
the characters.
The terminal will respond to select sequences and incoming text blocks with a WACK when
there are no input buffers available. The terminal will respond with an ACK as soon as a buffer
becomes available. Note that if too large a block is sent to the terminal following the ACK, it
may result in a buffer overflow and an EOT will be returned. In such a case, either reconfigure
the terminal to a larger buffer size, or reduce the buffer size of the host computer.
Memory is allocated from the terminal's display memory so that the larger the buffer size, the
smaller the amount available to display memory.
The output buffer size can range from 128 to 2048 bytes. It is set using the
~Bu
f
5
i
z e'
field of the
data comm configuration menu. The maximum input buffer size is determined by multiplying
~~Bu
f
5
i
z e"
by
HNumBu
f
5",
both as specified on the datacomm configuration menu. Refer to
"Choosing Buffer Sizes for Multipoint Configurations", in Section 3, for information on selecting
the buffer size.
Additional header and framing characters will be added to the output buffers depending upon
other configuration parameters specified.
SYN CHARACTERS. In asynchronous configurations you can use the
~~Ins
SYN" field to
cause SYN characters to be inserted at the beginning of each transmission and at
1
second
intervals until the end of the transmission. This is done automatically for sychronous con-
figurations.
TRANSPARENCY MODE (BINARY OPERATION). Transparency mode allows you to
send and receive 8-bit binary data. This allows the sending of data bit patterns that might
otherwise be interpreted as control characters.
7-37
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