Orientalmotor BLV Series, User Manual, Page: 32 / 40

Method of control via Modbus protocol
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4.12 Group send
Multiple slaves are made into a group and a query is sent to all slaves in the group at once.
• Group composition
A group consists of one parent slave and child slaves and
only the parent slave returns a response.
•
Group address
To perform a group send, set a group address to the child
slaves to be included in the group.
The child slaves to which the group address has been set
can receive a query sent to the parent slave.
Query (sent to
the parent slave)
Query (sent to
the parent slave)
Response
Master
Master
Parent slave
Child slave Executes the
process but does
not send a response.
• Parent slave
No special setting is required on the parent slave to perform a group send. The address of the parent slave
becomes the group address. When a query is sent to the parent slave from the master, the parent slave executes
the requested process and then returns a response (same as with the unicast mode).
• Child slave
Use a "Group" command to set a group address to each child slave.
Change the group in the unicast mode.
Address Setting range Initial value
0030h
−1: No group specification (Group send is not performed)
1 to 31: Sets a group address.
−1
Note
The group setting is not saved in the non-volatile memory even when the "Batch NV memory write" is
executed. Therefore, the group setting will be initialized when the driver power is turned off. Reset the
group setting whenever the power is turned on.
• Function code to execute in a group send
Function code Function
10h Writing to multiple holding registers
Programmable controller
or master device
Address 1
"Group" command: -1
(individual)
Address 2
"Group" command: 1
Address 3
"Group" command: 1
Parent
slave
Child
slave
Child
slave
Start of
operation
of address 1
Response
from
address 1
Motor operation
at address 1
(parent slave)
Motor operation
at address 2
(child slave)
Motor operation
at address 3
(child slave)
Start of
operation
of address 2
Stop of
operation
of address 1
Stop of
operation
of address 2
Response
from
address 2
Response
from
address 1
Response
from
address 2
Master to slave
Slave to master