User's Manual

905U-D Radio Modem Module User Manual
Page 14 © May 2000
DB9 Connector Pinout
Pin Name Direction Function
1 DCD Out
Data carrier detect - not connected Rev. 1.03 software & earlier
Rev. 1.04 & later - driven when link is established in controlled mode
- driven always in transparent mode
2 RD Out Transmit Data - Serial Data Output
3 TD In Receive Data - Serial Data Input
4 DTR In
Data Terminal Ready - not connected Rev 1.03 & earlier,
Rev. 1.04 & later: When in controlled mode, will autodial if destination
address is configured In control mode, an inactive DTR will force the 905U-
D to low-power mode.
Rev. 1.11 & later: When in controlled mode, will autodial if destination
address is configured In control mode, an inactive DTR will force the 905U-
D stop communicating by radio. If low power mode is selected, an inactive
DTR will also force the 905U-D to low power mode.
5 SG Signal Ground
6 DSR Out Data Set Ready - always high when unit is powered on.
7 RTS In Request to Send - hardware flow control
8 CTS Out Clear to send - hardware flow control
9 RI Ring indicator - not used or connected
Hardware handshaking using the CTS/RTS lines is provided. The CTS/RTS lines may be
used to reflect the status of the local unit’s input buffer, or may be configured to reflect the
status of CTS/RTS lines at the remote site. The 905U-D does not support XON/XOFF.
Example cable drawings for connection to a DTE host (a PC) or another DCE host (or
modem) are detailed below. These example are for transparent mode. Controlled mode
may require the use of DTR or DCD signals.
2.3.2 RS485 Serial Port
The RS485 port provides for communication between the 905U-D unit and its host device
using a multi-drop cable. Up to 32 devices may be connected in each multi-drop network.
Note that the RS485 port is shared internally with the RS232 port - make sure that the RS232
port is disconnected before using the RS485 port.