Transmitting Global-Control Commands - Omron SYSMAC CS Series Operation Manual

Operating the Network
6-6-3

Transmitting Global-Control Commands

Global-Control commands
I/O Data Synchronization
Note
Group Address Setting
Setting the Group
Address of a Slave Device
Freeze / Unfreeze
commands
The CS1/CJ1W-PRM21 PROFIBUS Master Units support the transmission of
Global-Control commands. These messages are unconfirmed broadcast
messages (i.e. the slave devices do not send a response message), which
can be used to synchronize I/O data related events two more slave devices.
Two types of synchronization can be achieved.
1. Synchronization of input data
The inputs on one or more slave devices are read at the same time. The
synchronized data is transferred to the Master Unit during the next I/O data
exchange cycle. The commands are defined as Freeze and Unfreeze.
2. Synchronization of output data
The outputs on one or more slave devices are set at the same time. The
synchronized data has been transferred to the slave devices during the
previous I/O data exchange cycle. The commands are defined as Sync
and Unsync.
1. The CS1/CJ1W-PRM21 PROFIBUS Master Unit also uses Global-Control
commands to broadcast its own operational mode to other devices on the
network. These Global-Control commands are sent automatically, without
user interference
• to all devices on the network (i.e. not to specific groups),
• always at the start of every I/O data exchange cycle, and
• only when the Master Unit is either in OPERATE or in CLEAR mode
2. The user can only initiate transmission of Freeze/Unfreeze and Sync/Un-
sync to either all slave devices or specific groups of slave devices. These
Global-Control commands are transmitted separately from the automati-
cally transmitted messages, at the end of the PROFIBUS I/O data ex-
change cycle.
User initiated Global-Control commands can be transmitted to either all slave
devices allocated to a Master Unit, or to one or more of up to eight groups of
slave devices. The group addresses are defined by up to eight bits in a group
address byte, which is part of the Global-Control command.
Note If a Global-Control command is targeted to all slave devices, all the group bits
in the group address bytes are set to 0.
In order for a specific slave device to belong to a certain group, the group
assignment for the slave has to be defined through the Generic Slave DTM
Configuration User Interface. A slave device can belong to one or more
groups at the same time, or to no specific group at all. The group assignment
is sent to the slave devices as part of the parameter message.
To define the group assignment of a slave device, through the Generic Slave
DTM, refer to section 6-3-3 Selecting the Group Assignment.
Sending a Global-Control - Freeze command to a slave device has the follow-
ing effect
• The slave device will continue to read its physical inputs, but not send this
data to the PROFIBUS Master Unit.
• Instead, it will continue to transfer the input data to the Master Unit from
the moment the Global-Control - Freeze command was received.
• If a new Global-Control - Freeze command is sent, the slave device will
update its PROFIBUS input buffers only once, with the most recent physi-
Section 6-6
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