Modbus Mode Communications - Hitachi SJ7002 Series Instruction Manual

ModBus Mode Communications

Transmission
The network master sends a frame to initiate communications with a slave, as shown in the
Procedure 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
The inverter always sends a response frame after receiving a query frame. The inverter does not
initiate any communication with the host (master).
Transmitting device:
Host
(master)
Inverter
(slave)
(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.
Function
Name/Description
Code
Action upon communi-
C076
cation error selection
Communication timeout before trip
C077
Limit timer for reception timeout
C078 Communication wait time
Time to wait until the inverter starts
sending a response after reception
of a query (excluding the silent
interval)
Query
Response
Latency time (silent interval plus C078 setting)
OPE
00 Trip (E41)
01 Trip (E41) after deceleration and stop
02 No action (ignore errors)
03 Free-run stop
04 Decelerate and stop
0.00 to 99.99 (seconds)
0.0 to 1000 (milliseconds)
SJ700 Inverter
2
Range and Settings
B–21