Control Data Corporation INFORMATION SYSTEMS TERMINAL II Hardware Maintenance Manual page 75

Request to Send (RTS), CA - This signal from the terminal
to a data set (modem) indicates that data to be transmitted
is available and the modem should condition the lines.
It is activated automatically. The interface, after
receiving data from the processor, holds the data and acti-
vates the RTS line. It keeps it activated until the last
bit of data has been clockea out.
Clear to Send (CTS), CB - This signal from the data set
must be active to enable the interface to transmit data.
It must follow the RTS signal.
Data Terminal Ready (DTR), CD - This signal is active as
long as the terminal is powered up.
Data Set Ready, CC - This signal from the data set is
passed on to the processor as a Status bit.
Carrier Detect - This signal from the data set is passed on
to the processor as a status bit.
Data Format
The send data and receive data serial information is asyn-
chronous. Figure 4-9 shows the serial data format. Both
the receive and send portions must operate with the same
format (number of data bits, stop bits, odd/even/no parity,
and baud rates). The Least Significant Bit (LSB) of the
character transmits first (after the start bit) and the
Most Significant Bit (MSB) last. The receiver takes the
first serial data bit as the LSB and the last one as the
MSB. The transmitter idles in the mark state.
The number of data bits is selectable by program control.
Parity or no parity is switch selectable (S2-5). If parity
is enabled, the even or odd selection is performed under
program control. The number of stop bits is switch
selectable.
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