Modbus Method - Omron RX2 Series User Manual

9-2

Modbus Method

Communications Procedure
The inverter communicates with an external controller as follows.
(1) Query
External
controller
Inverter
(1) Frame (Query) that is sent from the external control device to the inverter
(2) After receiving a query frame, the inverter waits for the total time of the Silent Interval and the Com-
munication Wait Time (CF-07), before returning a response.
Silent Interval
The wait time that is specified on Modbus communication; its data length is 3.5 characters
(3.5 bytes).
It depends on the Modbus communication speed setting.
(3) Frame (Response) that is sent from the inverter back to the external controller
(4) After sending a response, the inverter monitors the time until it completes receiving the query frame
from the external control device. The inverter judges it as a communications error if it receives no
response within the Communication Error Timeout Time (CF-06).
Then, the inverter operates according the Operation Selection on Communication Error (CF-05),
while waiting for the reception of the first data again.
The monitoring of the Communication Error Timeout Time starts from the first sending/receiving
operation is established after the power supply is cycled or after the inverter is reset.
The inverter does not recognize as a communications error timeout if the sending/receiving opera-
tion is not established at all.
For setting details, refer to the following information.
Parameter No.
CF-05
CF-06
CF-07
High-function General-purpose Inverter RX2 Series User's Manual
(3) Response
(2) Wait time (silent interval + CF-07)
Function name
RS485 communication
error selection
RS485 communication
0.01 to 100.00: Length of time to occurrence of
timeout setting
RS485 communication
wait time setting
9 Communications Functions
(1) Query
(4) Communication Error Timeout (CF-06)
(Operates according to Operation Selection on
Communication Error (CF-05) when reception times out.)
Data
00: Error
01: Trip after deceleration stop
02: Ignore
03: Free run
04: (Deceleration stop)
0.00: Function disabled
a communications error timeout
0 to 1000: Time to wait for response from
the inverter (exclude silent
inverter)
Time
Default
Unit
data
02
0.00 s
2 ms
9 - 5
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