Control Data Corporation 6000 Series Reference Manual page 18

TABLE 3-3. 6675 -DATA SET COMMUNICATION SIGNALS (Figure 2-2)
SIGNAL DESCRIPTION
Serial Clock Transmit
(SCT)
Send Data (SD)
Serial Clock Receive
(SCR)
Receive Data (RD)
Interlock (IT)
Carrier On-Off (COO)
Send Request (SR)
Clear-to-Send (CS)
Function Codes
The SCT circuit furnishes the master clock timing signals
for the DSC in the Transmit mode. The data set SCT
signal is a square wave (40. 8 KC- 301-B, 2. 4 KC- 201-B).
T]:ie SD line carries the serial data from the DSC to the data
sei: where the information is sampled during the negative
transition of the SCT square wave.
Similar to the SCT signal, the SCR signal clocks the
received data to the DSC. SCR synchronization depends
upon the SCT signals at the transmitting set.
RD consists of incoming serial data which is sent to the
DSC and sampled during the negative transition of the SCR
square wave.
An On signal to the DSC indicates that the data set is On,
that it can transmit data, and that it is not in a test
condition.
An On signal to the DSC indicates that the line carrier is
present at the data set.
The DSC delivers an On signal to the data set when it is
ready to transmit data. The data set should respond with
a CS signal.
When the SR circuit is turned On by the DSC, the CS circuit
should be switched On by the data set indicating that it will
accept data. When the SR circuit is again turned Off, the
CS circuit is switched off.
The 6675 translates and interprets the external function (EXF) codes listed in Table
3-4. The function codes represent commands or requests from the computer. The
EXF code format is as follows:
Rev. A
3-5