Oriental motor BLH Series - Group Send

87
Modbus RTU control (RS-485 communication)
11.7 Group send
With the group send, multiple slaves are made into a group and a query is sent to all slaves in the group at once.
The function code that can be executed in the group send is "Writing to multiple holding registers (10h)" only.
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Group composition
A group consists of one parent slave and child slaves and only the parent slave returns a response.
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Group address
To perform the 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.
The parent slave is not always required. A group can be
composed by only child slaves. In this case, set an unused
address as an address of the group.
When a query is sent from the master to the address of the
group, the child slaves execute the process.
Query
(to the parent slave)
Query
(to the parent slave)
Response
Master
Master
Pa
rent slave
Child slave No response
after execution
However, no response is returned. In broadcasting, all the slaves execute the process, however, the slaves that execute
the process can be limited in this method.
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Parent slave
No special setting is required on the parent slave to perform the group send. The address of the parent slave becomes
the group address. When a query is sent from the master to the parent slave, the parent slave executes the requested
process and returns a response. (Same as the unicast mode)
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Child slave
Slaves to which the address of the parent slave is set become the child slaves.
When a query sent to the address of the group is received, the child slaves execute the process. However, no response is
returned.
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Setting of Group
The methods to set a group are one of the following.
•
Set by the command
•
Set by the parameter
z
Set by the command
To set a group, set the address of the parent slave to the "Group ID" of the child slaves.
Change the group in the unicast mode. For reading and writing when setting the "Group ID," execute the upper and
lower parameters at the same time.
Related commands
Register address
Name Description Factory setting R/W
Dec Hex
48 0030h Group ID (upper)
Set a group address to the child slaves to be included in the group.
[Setting range]
−1: No group specication (group send is not performed)
1 to 15: The address (address of the parent slave) of the group
−1 R/W
49 0031h Group ID (lower)
Note
•
Do not set "0" to the group ID.
•
Change the group address in the unicast mode.
•
The group setting is not saved in the non-volatile memory even when the "Write batch NV memory" of the
maintenance command is executed (it is saved in the RAM). The group setting (Group ID) is returned to the initial
value when the power supply of the driver is turned o. Every time the power supply is turned on, reset the group
setting or set with the parameter.