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SYNCHRONOUS
TRANSMITTER-
RECEIVER
BUFFER (STRB),
MODEL 70/722
GENERAL DESCRIPTION
OPERATIONAL
CHARACTERISTICS
STRB/CCM Interface
Commands
Disconnect (DISC)
Transmit (TC)
Receive (RC)
70/722 Synchronous
Transmitter-Receiver
Buffer
• The STRB occupies one scan position on the Communication Controller-
Multichannel (CCM), Model 70/668; and enables it to exchange control and
bit- serial data signals with another STRB or with IBM Synchronous
Transmitter-Receiver terminals, via EIA-Standard data setso The character
length is fixed at eight bits. Operation is always half-duplex and syn-
chronous, with signal element or bit timing supplied to the data set by the
STRBo Such timing is derived from oscillators in the CCM and permits data
speeds up to 2400 bits per second. Optional capability is provided for using
the fast-turnaround provided by four-wire, half-duplex circuits.
• Control signals and data bits are exchanged between the STRB and CCM
in a prescribed sequence:
1.
The CCM Selects the STRB,
2. The STRB presents its status signals and data level,
3. The CCM issues command signals and a data level, and
4. The CCM drops Select, allowing the STRB to change its status
signals and data levels.
Note:
Signal and data levels are accepted by the STRB and CCM at Strobe
time o
• The command signals from the CCM are decoded by the STRB into the
following commands:
Disconnect (DISC)
Transmit (TC)
Receive (RC)
Terminate (TERC)
End Character (ECC)
• The DISC command restores the STRB and the data set to their quiescent
conditions such that a message network line is disconnected at the end of a
call and carrier is dropped on a pri vate line.
•
The TC command conditions the STRB, the data set, and the line for
data transmission.
•
The RC command conditions the STRB, the data set, and the line for
data reception.
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