PCIe-COM232-8 User Manual
15
Chapter 6: Connector Pin Assignments
Input/Output Connections
The serial communications ports are available to the user via a female 68-pin VHDCI D-
connector. There is an available breakout cable terminating in eight (or four) individual D-sub
9-pin connectors.
The cable is permanently labeled near each DB9 connector with the port letter. Four port
cards ordered with a breakout cable will have four D-sub 9-pin connectors, labeled as COM A,
COM B, COM C and
COM H
.
The RS-
232 specification allows for a maximum recommended length of 50’ due to the single-
ended signaling line drivers.
To ensure that there is minimum susceptibility to EMI and minimum radiation, it is important
that the card mounting bracket be properly screwed into place and that there be a positive
chassis ground. Also, proper EMI cabling techniques (cable connect to chassis ground at the
aperture, shielded twisted-pair wiring, etc.) should be used for the input/output wiring.
DB-9 Male Pin x=A-H
RS-232 Signal Names
Signal Descriptions
Ch x - 1
DCD
Data Carrier Detected
Ch x - 2
RX
Receive Data
Ch x - 3
TX
Transmit Data
Ch x - 4
DTR
Data Terminal Ready
Ch x - 5
GND
Signal Ground
Ch x - 6
DSR
Data Set Ready
Ch x - 7
RTS
Request To Send
Ch x - 8
CTS
Clear to Send
Ch x - 9
RI
Ring Indicator
Table 6-1: Connector Pin Assignments
For best results termination is recommended for any control signals not being used in your
application wherever possible. Typical applications accomplish this by connecting DSR and
DTR to DCD, as well as connecting the RI and CTS pins to the RTS pin.
Figure 6-1: Male DB9 Connector Pin Locations