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Configuring the Terminal
If you increase the buffer size, however, you may encounter another form of increased overhead
if you are operating in an environment in which retransmission is a common occurrence. In
manufacturing areas, for example, there is more chance of electrical interference on the line
than in an office environment. The longer the block ofdata being transmitted, the more chance
there is of encountering line interference during transmission. To retransmit a large block of
data three or four times would result in more overhead than that of transmitting three or four
smaller-sized blocks.
Therefore, you will also want to consider the physical environment in which the terminals and
their connecting cables will exist. In environments that are susceptible to electrical inter-
ference you may want to keep down the buffer size.
A good general approach is to start with the maximum size datacomm buffers
(BufSi ze=2048;
NumBu f
5
= 2)
and determine if that leaves you with an acceptable amount of display memory. If
it doesn't, then try a smaller
BufSi ze.
Be sure, ofcourse, not to exceed the maximum block size
that your host computer can handle. Once you have satisfactorily resolved the contention
between
Bu f S
i
z e
and display memory, the datacomm buffer configuration can only be judged
further by actually performing data communications. When the terminals are all configured
and connected to the computer system, use Monitor Mode or a line monitor to see how many
retransmissions are happening and to see if the terminal buffer sizes are reasonably compati-
ble with the transmit/receive requirements of the host computer. The use of Monitor Mode is
described under CCMultipoint Programming Information" in Section 7.
PROGRAMMATIC CONFIGURATION
Escape sequences can be used to change the active values of some configuration menu parame-
ters. Appendix A contains a list of the escape sequences, along with their functions. In addition
to changing configuration values, the configuration menus can be locked and unlocked, using
escape sequences.
Normally, escape sequences are transmitted to the terminal from a program operating on the
host computer; however, they can also be generated at the keyboard.
Configuration Escape Codes
To set configuration parameters using escape codes, you must use an
Ec
&k,
Ec
&5,
or
Ec )
sequence, depending upon which parameters you wish to set.
A change of a parameter value using the
Ec
& k
and
Ec
&5
sequences take effect immediately,
but the content of nonvolatile memory is not changed. If a configuration menu is displayed on
the screen when the escape sequence is received, the sequence is not executed until the menu is
exited.
3-27
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