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Receive (RC) and
Terminate (TERC)
Acknowledge
(ACKC)
Not-Acknowledge
(NAKC)
Disable (DIS)
Line Control-
Command/Response
Exchange
70/725 Data Gathering
System Buffer
The Receive command enables this unit to accept a message from the
line. Upon reception of an RC, the Buffer performs the following functions:
Sets idle current;
Senses RT from the line;
Responds with PT;
Permits carrier and phase detection;
Permits RDY when data is detected; and
Permits reports.
When an RC is terminated (TERC), this unit performs the following
functions:
Resets Read Command FF;
Inhibits PT generation, carrier and phase detection;
Inhibits all reports; and
Responds to SEL with END.
• The ACKC command causes the buffer to respond to a good message.
Upon receipt of an ACKC, this unit performs the following functions:
Transmits ACK (1280 cps) for 10 ms; and
Responds to SEL with END at start of tone o
• The NAKC command instructs the buffer to respond to a received
message which contained an error. Upon receipt of this command, this
unit performs the following functions:
Stores the NAKC
When carrier is removed from the line, it generates and transmits
NAK (1920 cps), and responds to SEL with END at start of toneo
•
The DIS command causes the buffer to remove the Idle current from the
line thus rendering it unavailable to the LC. After receipt of this command,
the buffer responds to SEL with END. To reinstate this buffer after a DIS,
a Halt Device command must be issued prior to the next RC
0
•
The sequence of CCM commands issued for line control purposes and
their corresponding buffer responses, depends on the message validation
scheme used by the system on the particular line. The following tables
show these sequences for CCM and program validation schemes, res-
pectively.
4-40
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