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Guide to the RLX-IFHS User Manual RLX-IFHS ♦ RadioLinx Industrial Wireless
User Manual RadioLinx® Industrial Frequency Hopping Serial Radios
Page 82 of 107 ProSoft Technology, Inc.
November 19, 2013
The following table contains the pin functions for both the DB25 and the DB9
connectors:
Pin Name Pin Number
DB9 / DB25 Function
Transmit Data (TXD) Pin 3 / 2 Serial Data Output
Receive Data (RXD) Pin 2 / 3 Serial Data Input
Clear-To-Send (CTS) Pin 7 / 4 This line indicates that the modem is ready to exchange data.
Data-Carrier-Detect (DCD) Pin 1 / 8 This line becomes active when the modem detects a carrier from the
modem on the other end of the phone line.
Data-Set-Ready (DSR) Pin 6 / 6 This tells the UART that the modem is ready to establish a link.
Data-Terminal-Ready
(DTR)
Pin 4 / 20 This tells the modem that the UART is ready to exchange data.
Request -To -Send (RTS) Pin 7 / 4 This line informs the modem that the UART is ready to exchange data.
Ring Indicator (RI) Pin 9 / 22 Goes active when modem detects a ringing signal
Signal Ground (SG) Pin 5 / 7 Signal ground
Communication signals diminish in strength as they travel through cable. The
maximum cable lengths for RS-232 are less than RS-485 because the RS-232
interface is more susceptible to noise. The data performance of RS-232 and RS-
485 is similar as long as the cable requirements are met. The following table
gives an estimation of the cable length requirements for the two serial interface
protocols:
Characteristic RS-232 RS-485
Maximum cable length 100 feet 4000 feet
Maximum bits/sec. 20kbps 100Mbps
There are different ways to transfer data serially; simplex, half-duplex, and full-
duplex.
Simplex communication mode allows transmission of data in one
direction only. In the half-duplex mode, data can be transferred in both
directions, but not simultaneously. That means data can be transferred over a
single pair of wires, but the data can only be transferred in one direction at a
time.
Full-duplex mode utilizes two pairs of wires and the data can be
transferred in both directions simultaneously.