Measurement Computing Serial488/4 - Manual (Page 28)

Section 1 Introduction
2.16
option (N0) is normally used. T his option w ill cause the Serial488/4 to
send XOFF and XON control characters depending on the amount of
memory available for receiving serial data. The manual handshake control
options (N1 and N2) may be used in special circumstances to send XOFF
and XON characters under program control if desired.
The clock output handshake control option (N3) operates the same as
the automatic handshake option, but will also cause the serial baud clock x
16 signal to be output on the RTS line.
In addition to softw are and hardw are handshaking the Serial488/4
provides a No Handshaking mode w hich may be used in special
circumstances where handshaking is not desired. This mode is selected by
using the G2 command. In the no handshake mode the RTS line may be
manually un-asserted or asserted using the N1 and N0 or N2 handshake
control commands, or the serial baud clock x 16 may be output on the RTS
line if the N3 command is used.
2.5.4 Serial Signal Descriptions
The Serial488/4 is equipped w ith four DB-9S connectors on its rear
panel and requires DB-9P mating connectors. The Serial488/4's connector
is configured as an IBM A
T when RS-232 levels are selected and
Macintosh II/SE/Plus when RS-422 levels are selected. Tables 2.2 and 2.3
list the RS-232 and RS-422 pin connections. E ach of these signals are
described below.
RxD- Receive Data (input)
This pin accepts serial data sent by an RS-232 or RS-422 device.
The serial data received is expected to
match the word length,
baud rate, stop bits, and parity configuration of the particular port.
This signal is low true.
RxD+ Receive Data (input)
This pin accepts serial data sent by an
RS-422 device. It
functions identically to RxD - except that its polarity is inverted.
This signal is high true.