AeroComm CL4424 Manuel D’Utilisation
CL4424 User’s Manual
6/21/2005
10
2. Interfacing Protocol
The CL4424 is a DCE (Data Communications Equipment). A DCE can be interfaced to a DTE
using a straight through serial cable (the serial cable provided with the CL4424 is a straight
through cable). Typically, PC’s are defined as a DTE and peripherals are defined as DCE. To
interface a DCE with another DCE, or a DTE with another DTE, a null modem (or a Crossover)
cable is required. The null modem simply swaps pins to convert a DCE to a DTE and vice-versa.
A null modem cable can be provided with the CL4424 on request.
using a straight through serial cable (the serial cable provided with the CL4424 is a straight
through cable). Typically, PC’s are defined as a DTE and peripherals are defined as DCE. To
interface a DCE with another DCE, or a DTE with another DTE, a null modem (or a Crossover)
cable is required. The null modem simply swaps pins to convert a DCE to a DTE and vice-versa.
A null modem cable can be provided with the CL4424 on request.
The CL4424 transceivers support the following interface protocols
• RS-232
• RS-485 (2-wire) Half Duplex
Table 1 – DTE, DCE and Null Modem Signal Definitions
DCE Pin
Number
DCE Signal
Name
DCE
Direction
DTE Pin
Number
Number
DTE Signal
Name
DTE
Direction
Null Modem
Female DB9
Null Modem
Male DB9
1 DCD O 1 DCD I 1 NC
2 TXD O 2 RXD I 2
3
3 RXD I 3 TXD O 3
2
4 DTR I 4 DTR O 4
6
5 GND 5 GND
5
5
6 DSR O 6 DSR I 6
4
7 RTS I 7 RTS O 7
8
8 CTS O 8 CTS I 8
7
9 RI O 9 RI I 9 NC