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Terminate (TERC)
End Character
(ECC)
Data Transfer
Initial Conditions
Synchroniz ation
70/722 Synchronous
Transmitter -Receiver
Buffer
•
The TERC command conditions the buffer to terminate a Transmit,
Receive, or Auto-Call command.
•
The ECC command sets the STRB character frame for receiving. The
STRB does not respond with END.
•
Whenever the STRB receives a SEL from the CCM, it responds with
BOP regardless of command status or line condition. In the absence of a
command, the STRB remains in the condition in which
it
is placed upon
termination (END) 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 STRB
is restored to its quiescent condition and the command which was present,
if any, is dropped. The STRB responds to a subsequent SEL with BOP, only;
until another command is received.
•
The STRB provides both character and bit synchronization with the remote
transmitter-receiver
o
While transmitting, the STRB employs a fixed-
character frame to which the remote receiver synchronizes. While receiv-
ing, the STRB relies on the CCMs character recognition capability to
establish the character frame. Once the CCM sets the frame via the ECC,
the STRB retains that frame until a new frame is set by the CCM. While
receiving, the STRBs bit detection point is initially fixed; and then
corrected (advanced or retarded) in accord with the received Signal
transitions. Each correction amounts to 3% of a bit time. This process is
described in detail in the appropriate IBM literature. The method of
achieving synchronous is as follows:
1.
Transmit -
If the STRB is to transmit, the program must first
enable synchronization by the remote receiver and receives an End
of Idle (EOI). To initiate this process, the program transmits a
minimum of 100 Idle characters, followed by an EOI. The program
then places the CCM and STRB in the receive mode and awaits
receipt of an End of Idle (EOI) Sequence. If EOI is not received in
3 seconds (program timing), the program resumes transmission of
Idles followed by EOI; and again goes to receive. When an EOI has
been received, the program can request permiSSion to transmit by
sending an Inquiry.
2.
Receive -
If
the STRB is to receive, the program must first enable
synchronization of the STRB. To initiate this process, the program
places the CCM and STRB in the receive mode and awaits receipt of
an End of Idle (EOI) or an Inquiry. If an EOI is received, the program
transmits a minimum of 100 Idle characters, followed by an EOI, and
again goes to receive. If an inquiry is received, the program trans-
mits the response.
4-31
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