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OW CONSTRUCTION
EXAMPLE NUMBER 2
(70/799 VIDEO
TERMINAL)
From Video Terminal
to Processor
STX - Start
Message
CCM Initialization
•
The following is an
qw
table established for the proper C CM detection
and control of a fictitious remote video display terminal. In this example,
the terminal can be one of a number on a multistation, half-duplex, private
line equipped for polling operation from the processor. The control codes
which must be set into OWs are defined as follows:
From Video Terminal to Processor
Start of Message
STX
End of Message
ETX
Transmit Start Code Answer Back
EOT
This example, as described, requires the accessing of OW-2 on one
occasion. The bit settings of the OWs are set to 1 or 0 to reflect the
necessity of:
1 -
take action.
o -
do not take action.
Based upon these OW requirements, the CCM hardware is set to reflect
in the LSWs the bit settings for the initial conditions: Receive/Transmit,
in data block/out of data block and the sequence counter.
•
1.
Receive/Transmit set to 1 - processor receiving NDB set to 0 -
system should be out-of-data block when STX is received. Sequence
counter setting is not necessary when this character is received.
2.
OW -1 Bit Setting
2, 1, 0 (Action control) -
001, unconditional action.
3 -
0 Not used.
2-10
4 -
1 STX should set NDB.
5 - 0 STX should not reset NDB.
6 -
0 Do not inhibit setting of sequence
counter.
8, 7 -
00 will not affect sequence counter when
Bit 6 is set to
O.
12-9 -
0000 no requirement to advise pro-
cessor of receipt of STX.
13 -
0 do not terminate existing command
(Read).
14 - 0 Exclude this character from BP count.
15 -
0 Do not ignore this character.
16 - 0 OW -2 not required.
17 -
Parity.
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