Delta RMC151 - Manual (Page 471)

6 Communication
the one it sent to the RMC when issuing the command, and it can then safely examine the
In Position bit.
Setting the Sync Register Mode
To select whether the Sync Register is used:
1. In the Project pane, expand the Modules folder, double-click the CPU module, and
choose EtherNet/IP.
2. Under Sync Register, select either Use a Sync Register or Do not use a Sync
Register. The second option requires RMC70/150 firmware 3.39.0 or newer.
Using Input Data in the PLC
If the Sync Register is used, then the first register is reserved as the Sync Register. All
other registers in the Input Data are controlled by the Outgoing Cyclic I/O Data address
specified in the EtherNet/IP Settings Page. When the I/O connection is established, the
Input Data is automatically updated in the PLC at the Requested Packet Interval (RPI).
The PLC can simply use the data whenever it needs it. The RMC does not wait for the
Sync Register to change to update its Outgoing Cyclic I/O Data.
Care must be taken to consider the data types of each Input Data register. The RMC
includes registers of type REAL, DINT, and DWORD, and when you assign the Outgoing
Cyclic I/O Data, you have the ability to mix registers of different types in the Input Data.
It may be necessary to copy the data from one type of memory to another in the PLC to
ensure that it gets interpreted correctly. For example, on Allen-Bradley PLCs, the COP and
CPS instructions can be used to copy the data from an array of one type to tags of the
correct type.
Writing Output Data with a Sync Register from the PLC
To write data in the RMC controller using I/O data when the Sync Register is used, do the
following in the PLC:
1. Wait for the Sync Registers in the Input Data and Output Data to match.
2. Update any Output Data register values, except the Sync Register.
3. Change the value of the Output Data Sync Register.
4. Do not change any Output Data registers until the Input and Output Sync Registers
match again.
The RMC will apply the Output Data register contents only once.
Writing Output Data without a Sync Register from the PLC
To write data in the RMC controller using I/O data without the Sync Register, simply
change the Output Data registers in the PLC and they will get applied in the RMC. Often
care must be taken as to the order that the registers are updated to ensure that actions
triggered by changes to registers in the RMC have updated values for any parameters
they use. It is often necessary to also understand whether the I/O data is updated
synchronously to the PLC scan or not.
Writing to the Command Area from the PLC
The Incoming Cyclic I/O Data area can be set up to point to the Command Area registers
directly, or indirectly through the Indirect Data Map. The Sync Register should always be
used if the PLC will be writing commands to the Command Area. The following sequence
is recommended:
1. Wait Until the Sync In and Sync Out Registers Match
If they do not match, then this means that another command or set of commands is in
progress.
2. Clear Old Commands from the Command Registers
Clear old commands from the command registers for each axis. Otherwise, when the
Sync Out register is changed, the commands would be re-issued. One method of
clearing the old commands is to fill the Output Data array with zeroes.
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