Interfaces
25
CM1-86DX3
Note
: The shaded table cells denote power or ground. The * symbol indicates the signal is Active Low.
Table 3-2: Serial Port 3 (CN17) & Port 4 (CN18) Interface Pin Signals
Pin #
Signal
DB9 #
Description
1
DCD*
1
Data Carrier Detect – Indicates external serial device is detecting a carrier
signal (i.e., a communication channel is currently open). In direct connect
environments, this input is driven by DTR as part of the DTR/DSR
handshake.
2
DSR*
6
Data Set Ready – Indicates external serial device is powered, initialized,
and ready. Used as hardware handshake with DTR for overall readiness.
3
RXD
2
Receive Data – Serial port receive data input is typically held at a logic 1
(mark) when no data is being transmitted, and is held “Off” for a brief
interval after an “On” to “Off” transition on the RTS line to allow the
transmission to complete.
4
RTS*
7
Request To Send – Indicates serial port is ready to transmit data. Used as
hardware handshake with CTS for low level flow control.
5
TXD
3
Transmit Data – Serial port transmit data output is typically held to a logic 1
when no data is being sent. Typically, a logic 0 (On) must be present on
RTS, CTS, DSR, and DTR before data can be transmitted on this line.
6
CTS*
8
Clear To Send – Indicates external serial device is ready to receive data.
Used as hardware handshake with RTS for low level flow control.
7
DTR*
4
Data Terminal Ready – Indicates serial port is powered, initialized, and
ready. Used as hardware handshake with DSR for overall readiness.
8
RI*
9
Ring Indicator – Indicates external serial device is detecting a ring
condition. Used by software to initiate operations to answer and open the
communications channel.
9
GND
5
Ground
10
Key/NC
NC
Key Pin – Not connected
