Fuji Electric FRENIC-Ace series, User Manual

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9.1 Overview of RS-485 Communication
9-8
9.1.4 RS-485 connection devices
This section describes the devices required for connecting the inverter to a PC having no RS-485 interface or for
connecting two or more inverters in multi-drop network.
[ 1 ] Converter
In general, PC is not equipped with an RS-485 port. Therefore, an RS-232C–RS-485 or USB–RS-485 converter is
required. To use the equipment properly, be sure to use the converter which meets the mode below. Be careful that
a converter not recommended may not work properly.
Requirements for recommended converters
Send/receive switching system: Auto-switching by monitoring the transmission data at PC (RS-232C)
Electric isolation:
Electrically isolated from the RS-485 port
Fail-safe: Fail-safe facility (*)
Other requirements: Superior noise immunity
Note: The fail-safe function refers to a feature that ensures the RS-485 receiver’s output is at “logic high” even if
the RS-485 receiver’s input is opened or short-circuited or all the RS-485 drivers are inactive. (Refer to
“Figure 9.1-4 Communication Level Conversion”.)
Recommended converters
System Sacom Sales Corporation (Japan) : KS-485PTI (RS-232C-RS-485 converter)
: USB-485I RJ45-T4P (USB-RS-485 converter)
Send/receive switching system
The RS-485 communication system of the inverter acts in half-duplex mode (2-wire), so the converter must have a
send/receive switching function. Generally, the switching system may be either one of the followings.
(1) Auto-switching by monitoring the transmitted data
(2) Switching by RS-232C control signal (RTS or DTR) from the computer
Figure 9.1-4 Communication Level Conversion
Computer
Lev
el
c
onv
er
si
on
Driver
Receiver input
Send/ receive
switch
Driver
enable
Receiver output
Receiver enable
Receiver
Driver
Receiver input
Driver enable
Receiver output
Receiver enable
Receiver
RS-232C
—
RS-485 converter
FRENIC-Ace (two-wire system)