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Terminate (TERC)
End Character
(ECC) - Model
70/720-11, Only
Data Transfer
Initial Conditions
Transmit
General - All
Models
TWX - Model
70/720-11
70/720 Asynchronous
Data Set Buffer
•
The TERC command conditions the buffer to terminate a Transmit,
Receive, or Auto-Call command.
•
The ECC command indicates to the buffer when the last bit of a
character has been transmitted.
•
Normally the buffer transfers data from the CCM to the data set, and
vice versa, with the sense (lor 0) unchanged; as indicated in subsequent
sections.
• Whenever the buffer recei ves a SEL from the CCM, it responds with BOP
regardless of command status or line condition. In the absence of a com-
mand, the buffer remains in the condition in which it is placed upon
termination of the previous command.
It
is then conditioned to receive a
new command.
Whenever a signal appears on the Reset lead from the CCM, the buffer
is restored to its quiescent condition and the command which was present,
if
any, is dropped. The buffer responds to subsequent SEL's with BOP
only until another command is received.
•
The buffer executes a TC as indicated. Upon receipt of CTS (and
optionally, either RD or SRD) from the data set; the buffer responds to a
CCM SEL with RDY. A bit is received from the CCM on the Data leado
It
is transferred to bit storage and then to the data set TD lead with the same
sense (lor 0) as received from the CCM. Thereafter, the buffer becomes
RDY and transfers the second bit to storage. By means of bit timing which
the buffer derives from a CCM oscillator, the second bit is transferred to
the TD lead at the proper time. Subsequently, bits are transferred to storage
and then to the TD lead until TERC is received along with the last bit to be
transmitted. Thereafter, the buffer inhibits RDY, transfers the last bit to
the TD lead, and terminates as indicated. The buffer places a marking (1)
bit on the line unless a spacing (0) bit is made available by the CCMo The
buffer does not become RDY when CTS is off.
•
In addition to the functions described in the preceding section, TWX
operation accommodates the restraint function imposed by the TWX inter-
face. Thus, during TWX transmission, the buffer monitors the RDT signalo
When RDT goes on, the buffer stops transmission by inhibiting RDY to the
CCM after receiving an ECC from the CCMo The buffer resumes trans-
mission when RDT goes off.
If
the buffer detects RC spacing for Xms it
reports space detected, inhibits RDY, and transmits the bits already
received from the CCM. When RD returns to .marking transmission is
resumed.
4-17
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