F485 COMMUNICATIONS CONVERTER – INSTRUCTION MANUAL
5
Configuration
The converter box is configured via two internal dip switch banks which are accessible by
removing the converter box cover. Switches A1-A8 are used to set the baud rate for RS485
communications and determine whether the converter is DTE (RS232 direct) or DCE (RS232
modem). Switches B1-B6 are used to select the interface type. The designator for each
switch is clearly marked on the printed circuit board. The tables shown provide a
description of each switch within the switch banks.
Table 1: Switch A (baud rates)
Table 2: Switch A (DTE/DCE)
Table 3: Switch B (configuration)
Baud rates
Two-wire RS485 is half duplex and requires a means for switching between a receive or
transmit state. The F485 converter uses the incoming data to control the direction and
therefore requires no control signals from the master device (RS232 or fiber) to switch from
transmit to receive mode after the last character has been transmitted. The baud rate
switches control the length of time that the RS485 transmitter will remain in the transmit
direction after the last character has been transmitted. The length of time is fixed at 3.5
character times at the selected baud rate making it suitable for use with Modbus® RTU
protocol. When converting RS232 to FIBER, these switches (A1-7) have no effect.
BAUD
A1
A2
A3
A4
A5
A6
A7
1200
ON
OFF
OFF
OFF
OFF
OFF
OFF
2400
OFF
ON
OFF
OFF
OFF
OFF
OFF
4800
OFF
OFF
ON
OFF
OFF
OFF
OFF
9600
OFF
OFF
OFF
ON
OFF
OFF
OFF
19200
OFF
OFF
OFF
OFF
ON
OFF
OFF
38400
OFF
OFF
OFF
OFF
OFF
ON
OFF
57600
OFF
OFF
OFF
OFF
OFF
OFF
ON
MODE
A8
DTE
OFF
DCE
ON
CONFIGURATION B1
B2
B3
B4
B5
B6
RS232 TO RS485
OFF
ON
OFF
ON
OFF
OFF
RS232 TO FIBER
OFF
OFF
OFF
OFF
ON
ON
RS485 TO FIBER
ON
OFF
ON
OFF
OFF
OFF
