SJ700
2
Inverter
Appendix B
B–21
ModBus Mode Communications
Transmission
Procedure
The network master sends a frame to initiate communications with a slave, as shown in the
figure below.
• Query - A frame sent from the external control equipment to the inverter
• Response - A frame returned from the inverter to the external control equipment
• Wait time (C077) - If the inverter cannot complete the reception of a query from the host
(master)within the communication timeout period, the inverter responds to the query and
waits to receive the query from the beginning. Subsequently, the inverter returns no response
to the master system.
After reception timeout occurs, the inverter operates according to function C076, Action
upon communication error selection (see table below). Monitoring of reception timeout
begins when the first communication is performed upon inverter powerup or a reset.
Reception timeout is monitored only when the inverter communicates with the master
system.
The inverter always sends a response frame after receiving a query frame. The inverter does not
initiate any communication with the host (master).
Function
Code
Name/Description
OPE
Range and Settings
C076
Action upon communi-
cation error selection
00
Trip (E41)
01
Trip (E41) after deceleration and stop
02
No action (ignore errors)
03
Free-run stop
04
Decelerate and stop
C077
Communication timeout before trip
0.00 to 99.99 (seconds)
Limit timer for reception timeout
C078
Communication wait time
0.0 to 1000 (milliseconds)
Time to wait until the inverter starts
sending a response after reception
of a query (excluding the silent
interval)
Host
(master)
Latency time (silent interval plus C078 setting)
Query
Inverter
(slave)
Response
Transmitting device: