RCA 70/700 Series Reference Manual page 19

Channel
Coordination
(Cont'd)
CCM
3. Operational Words (OW) established by the program and stored in
CCM memory. The OWs direct further CCM action and are
addressed as described in 2. above and in Figure 1-2. Up to 64
two-word sets (OW-I, OW-2) may be provided for each CCM, with
each word comprising 18 bits including parity. The breakdown of
the OWs is given in Section 3, tables 3-5 and 3-6.
40 The In Data Block (NDB) indicator bit in each set of LSWs permits
two different OWs to be accessed upon recognition of a specific
control character as a means of generating discrete actions
o
All
characters which cause fetching of an OW are transferred to the
processor regardless of the setting of NDB, unless inhibited by the
OWo For systems which do not use the NDB control function, the bit
must be set upon initialization of CCM memory by the program
o
In systems using the NDB control function, the bit is set and reset
by OWo
It
will be reset, where called for by systems classification,
by processor initiation of a Read, Write, or Write Control command
but not as a result of command chaining.
5. Sequence Counter: Four different sequence counter indications per-
mit the accessing of four different OWs for any given combination
of system classification, character recognition, and transmit/
receive status o This capability enhances recognition of multi-
character sequence recognition.
6. Special Considerations (LSW F14): This consideration is applicable
only to use with certain systems where specific control characters
which must be recognized for functional purposes, can also be used
as data characters in the text of the message. Refer to table 3-40
7. Next Character Block Parity (LSW B13): This indication specifies
that the character following it is to be recognized as a block parity
character.
After each incoming character is transferred to the character transfer
store area of the LSW B, and eachoutgoing character is received from the
processor, it is decoded as described in 2 above. If a hit results, the
addressed OW-l is fetched and appropriate action is taken as indicated in
table 3-5 0
If
indicated by OW-I, OW-2 is also fetched to provide required
additional information. If no hit results, the character has no channel
coordination significance and is handled as data.
Certain operations called for by system classification are performed
by the CCM without reference to OWs. The upshift and downshift functions
of IBM 1050 and 2741 systems and the Figs and Ltrs functions of Baudot
coded telegraph equipment are performed directly by CCM logico These
shift functions are inserted automatically when transmittingo
If
it is
desired to exclude these shift characters from the processor when re-
ceiving, the proper OWs must be established o The detection and genera-
tion of SYN where appropriate in synchronous systems are performed by
CCM logic without reference to OWs. Except for the exclusion of shift
1-13