Connection Devices - Fuji Electric FRENIC-AQUA series User Manual

2.2.3

Connection devices

This section describes the devices necessary for connecting a host not equipped with RS-485
interface, such as a computer, or for multidrop connection.
[ 1 ] Converter
In general, personal computers are not equipped with an RS-485 port. An RS-232C to RS-485
converter or USB to RS-485 converter is therefore required. Use a converter meeting the
following recommended specifications for proper operation. Note that proper performance may
not be expected from a converter other than the recommended one.
Specifications of the recommended converter
Transmission/receiving switching system:
Isolation
Failsafe:
Other requirements: The converter must have enough noise immunity for successful
*1 The failsafe function means a function that keeps the RS-485 receiver's output at high logic level
even when the RS-485 receiver's input is open or short-circuited or when all the RS-485 drivers
are inactive.
Recommended converter
System Sacom Sales Corporation (Japan) : KS-485PTI (RS-232C to RS-485 converter)
Transmission/receiving switching system
Since RS-485 communications adopts the half-duplex system (two-wire system), the converter
must have a transmission/receiving switching function. The following two systems are available
as the switching system.
(1) Automatic turnaround of the transceiver buffer
(2) Switching with the flow control signal (RTS or DTR) from the personal computer
In the case of FRENIC Loader, the operating system released before Microsoft Windows98 or
an older version does not support the switching system described in (2) above. Use the
converter described in (1).
Personal
Computer
RS-232C
[ 2 ] Branch adapter for multidrop
The inverter uses an RJ-45 connector (modular jack) as a communications connector. For
multi-drop connection using a LAN cable having an RJ-45 connector, a branch adaptor is
required.
Recommended branch adapter
SK Kohki (Japan): MS8-BA-JJJ
Automatic switching by monitoring transmission
data on the personal computer side (RS-232C)
The RS-232C side of the converter must be isolated from the RS-485
side.
Equipped with a failsafe function (*1)
communications.
: USB-485I RJ45-T4P (USB to RS-485 converter)
Figure 2.8 Communications level conversion
2-13
2.2 Connections
FRENIC Series (two-wire system)