LSI M-Three Operator's Manual page 43

8.3 RS232 'HANDSHAKE' PROTOCOLS
These Handshake signals are used for communication between the
M-TH REE (DeE) and a local Data Terminal Equipment (DTE)
e.g. a VDU.
8.3.1 Request To Send [RTS] (25-way RS232 SKT. Pin
4)
This input to the M-TH REE goes 'high' when the DTE is
ready for data transmission.
8.3.2 Clear To Send [CTS] (25-way RS232 SKT. Pin 5)
This is output from the M-THREE as a 'high' level when
it is ready to receive data and in response to an RTS.
8.3.3 Data Set Ready [DSR] (25-way RS232 SKT. Pin
6)
This is output from the M-TH REE as a 'high' level when it
has attempted to establish
a
communications link with a
remote DeE (e.g. another M-THREE). It does not
necessarily indicate that a communications link actually
exists between the local and remote DeE's, just the status
of the local DeE when it has completed all of the timing
functions and generated the necessary answer tones.
8.3.4 Data Terminal Ready [DTR] (25-way RS232 SKT. Pin 20)
This input to the M-TH REE goes 'high' when the DTE is
ready to transmit data. This level must remain 'high' in
order to maintain a communications link between the local
and remote DeE's. If the signal goes 'low' the link will be
aborted.
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