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102
Operating the Network
Section 3-6
Sync / Unsync commands
Sending a Global-Control - Sync command to a slave device has the following
effect
• The slave device will update its physical outputs only once with the last
received PROFIBUS output data, despite new output data being received
from the PROFIBUS Master Unit.
• If a new Global-Control - Sync command is sent, the slave device will
update its physical outputs only once, with the most recent received out
put data.
• If a Global-Control - Unsync command is sent, the slave device will revert
back to its original situation, and transfer updated output information to
the Master Unit with each subsequent I/O data exchange message.
Note
If a Global-Control command contains both a Sync and an Unsync command,
the Unsync will prevail.
The figure shown below illustrates the Sync / Unsync feature as implemented
by the CS1/CJ1W-PRM21 PROFIBUS Master Unit.
Note
The Global-Control command as set in the CIO words is transferred to the
Unit together with the I/O data, but the Global-Control command is sent over
the PROFIBUS network, following the I/O data. This means that the outputs of
the targeted slave device will be updated with the values sent to the slave
prior to the Global-Control command.
Transmitting Global-
Control Commands using
CX-Profibus
CX-Profibus provides a means to transmit Global-Control commands from the
PC, through the CS1/CJ1W-PRM21 Master DTM Diagnosis User Interface -
Online Operations tab. This means uses the same CIO words as described
above
To accomplish a Global-Control command transmission, per from the follow-
ing sequence.
1,2,3...
1.
Make sure the CS1/CJ1W-PRM21 Master DTM is online with the PROFI-
BUS Master Unit.
2.
Open the CS1/CJ1W-PRM21 Master DTM Diagnosis User Interface.
PLC Cycle
PROFIBUS Cycle
Slave Output
Refresh Cycle
Global-Control Sync command
Sync
transmitted
Sync
transmitted
Instruction
Execution
Instruction
Execution
Instruction
Execution
Instruction
Execution
Sync command causes
immediate refresh of
slave outputs with last
received PROFIBUS
output data.
Sync command causes
immediate refresh of
slave outputs, and
freezes slave output
refresh process.
Global-Control Unsync command
Unsync
transmitted
Unsync command
cancels Sync command
and causes immediate
refresh of slave outputs
and with last received
PROFIBUS output data.