Measurement Computing Serial488/4 - Manual (Page 29)

Section 2 Getting Started
2.17
TxD- Transmit Data (output)
This pin transmits serial data to an RS-232 or RS-422 device. The
serial data received is sent with the word length, baud rate, stop
bits, and parity configured for the particular port. This signal is
low true.
TxD+ Transmit Data (output)
This pin transmits serial data to an
RS-422 device. The pin
functions identically to TxD- except that its polarity is inverted.
This signal is high true.
CTS+ Clear To Send (input) / 16 x Baud Clock (input)
The CTS+ input is used as a hardware handshake line to prevent
the Serial488/4 from transmitting serial data to an RS-232 or RS-
422 device w hen it is not able to accept it.
When RTS/CTS
handshaking is selected using the ( G0) command, the Serial488/4
will not transmit data out TxD+ while this signal is un-asserted
(low). If XON/XOFF (G1) or no handshaking ( G2) is selected,
the CTS+ line is ignored when transmitting data.
If XON/XOFF (G1) or no handshaking (G2) is selected the CTS
line may be used to input a clock signal which is sixteen times the
desired baud rate. T his mode is selected using the Baud Rate
command (B11).
CTS- Clear To Send (input) / 16 x Baud Clock (input)
The CTS- input is used as a hardware handshake line with RS-422
devices. The pin functions identically to CTS+ except that its
polarity is inverted. This signal is low true.
RTS+ Request To Send (output) / 16 x Baud Clock (output)
The RTS+ output is used as a hardware handshake line to prevent
an RS-232 device from transmitting serial data to the Serial488/4
when it is not able to accept it. When automatic
RTS/CTS
handshaking is selected using the ( G0) and (N0) commands, the
Serial488/4 will assert (high) the RTS+ signal when greater than