Fuji Electric FRENIC-VG Series - 5.2 Fuji General-purpose Communications

5.2 Fuji General-purpose Communications
5-19
Chap. 5 USING STANDARD RS-485
5.2 Fuji General-purpose Communications
5.2.1 Message format
Polling/selecting is used for the response message format. The inverter is in a constant standby state,
waiting for either selecting (write request) or polling (read request) from the host (PC, PLC).
The inverter receives a request frame with the same station address from the host while in the
standby state. If the frame is received normally, the request is processed and a positive response
frame (in the case of polling, the data is returned with the response) is returned. If the frame is not
received normally, a negative response frame is returned. In the case of a broadcast (all-station
selecting), no response is returned.
Explanation: Broadcast (all-station selecting)
If the station number (station address) of a frame is set to "99", it is processed by all inverters as a
broadcast. By using a broadcast, you can execute run commands and frequency commands for all
inverters simultaneously. (This is enabled only for S codes with standard frames, and a to f and m
commands with W, E, and option frames.)
5.2.2 Transmission frame
There are two types of transmission frame: a standard frame which allows you to use all
communications functions, and an option frame which allows you to perform high speed
communications but is restricted to monitoring and sending commands to the inverter.
With both the standard frame and option frame, all constituent characters (including BCC) of the
frame are displayed as ASCII characters. The table below shows the transmission frame length for
each of these frame types.
Frame type Frame length
Request 16 byte Selecting
Response 16 byte
Request 16 byte
Standard frame
Polling
Response 16 byte
Request 12 byte Selecting
Response 8 byte
Request 8 byte
Option frame
Polling
Response 12 byte
Response frame
Response + data
Read re
q
uest
Request frame
Host
Inverter
Response
Write request + data
Response frame
Request frame
Host
Inverter
Write request + data
Request frame
Host
Inverter