CL4490 Hardware Integration Guide
Version 1.0
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9
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Table 2: CL4490 DB9 Male Connector Pinout (as defined in CL4490)
Interfacing to Other RS232 Equipment
The CL4490 is a DCE (Data Communications Equipment) device. Typically, devices like PCs are considered
DTE (Data Terminal Equipment) devices. Peripheral devices are classified as DCE. A DCE device can interface
to a DTE device using a straight-through serial cable. When interfacing two DCE (or two DTE) devices
together, a null modem (or crossover) cable is required to swap pins and convert the signals accordingly.
Figure 2: DTE to DCE interface (signals with
respect to DTE)
Figure 3: DCE to DCE interface (signals with
respect to DTE)
Note: When using a pair of CL4490s to connect a PC to a peripheral unit, if you previously used a
straight-through serial cable to connect your PC to your peripheral device, you’ll need to use a
straight-through serial cable between the PC and the CL4490 and a null modem adapter, or cross-
over cable, between the other CL4490 and the peripheral device.
DB9 Pin Signal Name
Description
Direction
1
DCD
Data Carrier Detect
Out
2
TXD (RXD with respect to DTE) Transmit Data
Data Out to Host
3
RXD (TXD with respect to DTE) Receive Data
Data In to CL4490
4
DTR
Data Terminal Ready
In
5
GND
Ground
-
6
DSR
Data Set Ready
Out
7
RTS
Request to Send
In
8
CTS
Clear to Send
Out
9
RI
Ring Indicator
Out
