C04MUNICATI0NS SECTION 6.7
6.7.6.5.2 Buffer Length - (Memory locations F854--F855, 63572-63573)
6.7.6.5.3
6.7.6.5.4
6.7.6.5.5
VER.V09F
This is a two byte number which defines the maximum length of a
block.
It has a permitted range of 10-512 with a default of
200. The block length must be greater than the selected record
length. This control is useful for adjusting the throughput for
good or bad telephone lines when transmit ting over modems or
acoustic couplers. For a good line, the buffer length could be
set to maximum so that line turnarounds are kept to a minimum
and the maximum data is sent in one block. If, however, the
line is a bad one, then if the buffer length is set to a single
record length, the amount of data to be re-transmitted in the
event of a NAK or data corruption due to the bad line, is kept
to a minimum. On Receive, the block length can be anything up
to 512 characters.
It should be remembered that the block includes all control
characters and record separators.
Single Record Flag - (Memory location F856H or 63574)
This flag controls whether there is single or multiple records
in a bloc~ If set to zero (default value) there will be
multiple records in each block. If set non-zero, there is only
one record transmitted per block.
Record Padding flag - (Memory location F857 or 63575)
This single byte flag is used to control record padding. If
this byte is set to non-zero, a record is padded with spaces to
its maximum length as defined by record length before being
transmitted. On receiving a record, trailing spaces are
stripped off. If this flag is set to zero, record padding is
inhibited and trailing spaces are not stripped on reception.
The default state of this flag is zero.
Record padding is only normally used on fixed length 2780
communications.
Mode flag - (Memory location F858 or 63576)
This flag determines the essential difference between 2780 and
3780,
It selects between terminating a record with US (IFH),
followed by CRC, or with IRS (IEH) followed by CRC.
2780 mode is the default with the mode flag set to O. A non-
zero flag selects 3780.
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