D2 W MDME 2400 Wireless Ethernet Modem
IF 1584 Rev. 1
IF 1584 Rev. 1
Page 14
RS232 signals. The D2 W MDME 2400 is configured as DCE equipment with the pin-outs
detailed below.
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. The D2 W MDME 2400 does not support
XON/XOFF.
Example: cable drawings for connection to a DTE host (a PC) or another DCE hosts (or modem) are
detailed above.
DB9 Connector Pin-outs:
Pin Name Direction Function
1 DCD
Out
Data carrier detect
–
2 RD Out
Transmit Data
– Serial Data Output
3 TD In
Receive Data
– Serial Data Input
4 DTR In
Data Terminal Ready
-
5 SG
Signal Ground
6 DSR Out
Data Set Ready
- always high when unit is powered on.
7 RTS In
Request to Send -
8 CTS Out
Clear to send -
9 RI
Ring indicator
-
2.4.2 RS485 Serial Port.
The RS485 port provides for communication between the D2 W MDME 2400 unit and its host
device using a multi-drop cable. Up to 32 devices may be connected in each multi-drop network.
As the RS485 communication medium is shared, only one of the units on the RS485 cable may
send data at any one time. Thus, communication protocols based on the RS485 standard require
some type of arbitration.
RS485 is a balanced, differential standard, but it is recommended that shielded, twisted pair
cable be used to interconnect modules to reduce potential RFI. It is important to maintain the
polarity of the two RS485 wires. An RS485 network should be wired as indicated in the diagram
below and terminated at each end of the network with a 120 ohm resistor. On-board 120 ohm
resistors are provided and may be engaged by operating the single dip switch in the end-plate
next to the RS485 terminals. The dip switch should be in the “1” or “on” position to connect the
resistor. If the module is not at one end of the RS485 cable, the switch should be off.
