5-45
5 Operation
CJ-series PROFIBUS Master Unit Operation Manual for NJ-series CPU Unit (W509)
5-6 Operating the Network
5
5-6-3 Transmitting Global-Control Commands
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. The Freeze command forces an immediate update of the PROFIBUS transmis-
sion buffers in the slave device, with the last input value sampled. This input data is then
transferred to the PROFIBUS Master Unit, with the next I/O data exchange cycle.
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 out-
puts only once with the most recently received output 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 CJ1W-PRM21
PROFIBUS Master Unit.
CPU Cycle
Global-Control Freeze command Global-Control Freeze command
Global-Control Unfreeze command
Freeze command freezes
slave input refresh process.
Last input data transferred to
transmit buffer will be
transferred over PROFIBUS.
Freeze command causes
immediate update of transmit
buffer. Last sampled data will be
transferred over PROFIBUS.
Unfreeze command cancels
Freeze command and causes
immediate update of transmit
buffer. Input refresh process
started again.
Instruction
Execution
Instruction
Execution
Instruction
Execution
Instruction
Execution
Freeze
transmitted
Freeze
transmitted
Unfreeze
transmitted
PROFIBUS
Cycle
Slave
PROFIBUS
Input Buffers
Slave Input
Refresh Cycle
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