Measurement Computing Serial488A - Manual (Page 29)

2.19
RTS Request To Send - Output - Pin 5
The RTS output is used as a hardware handshake line to prevent
the RS-232/RS-422 host from transmitting serial data if the
Serial488A is not ready to accept it. When RTS/CTS handshake
is selected on the internal switches, the Serial488A will drive the
RTS output high when there are greater than 1000 character
locations available in its internal buffer. If the number of available
locations drops to less than 1000, the Serial488A will un-assert
(low) this output. If Xon/Xoff handshake is selected, the RTS line
will be permanently driven active high.
Vtest Test Voltage - Output - Pin 6
This pin is connected to +5 volts through a 1K• resistor. It is also
common to Vtest on pin 9.
Gnd Ground - Pin 7
This pin sets the ground reference point for the other RS-232
inputs and outputs.
Vtest Test Voltage - Output - Pin 9
This pin is connected to 5 volts through a 1K• resistor. It is also
common to Vtest on pin 6.
+RxD Receive Data Plus - Input - Pin 14
This pin accepts serial data sent by the RS-422 host. The serial
data is expected with the word length, baud rate, stop bits and
parity selected by the internal switches. The signal level is high
true and only connected to this pin when RS-422 operation is
selected. It is 180° out of phase with -RxD.
+TxD Transmit Data Plus - Output - Pin 16
This pin transmits serial data to the RS-422 host. The serial data
is sent with the word length, baud rate, stop bits and parity
selected by the internal switches. The signal level is high true and
only connected to this pin when RS-422 operation is selected. It is
180° out of phase with -TxD.