Omron 3G3MV-PDRT2, User Manual

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Chapter 2
2-11
Example System Startup
2-4-2 Starting the System
Turn ON the communications power supply and the power to other nodes in the following order.
1.Turn ON the communications power supply.
2.Turn ON the power to each Slave.
3.Turn ON the power to the DeviceNet (Master) Unit.
Note The power supplies listed above can all be turned ON simultaneously. The external I/O power
supply can be turned ON at any time.
2-4-3 Creating and Registering Scan Lists
Scan lists are lists that register the information that is transferred between DeviceNet (Master) Units
and Slaves. The DeviceNet (Master) Unit compares the scan list with the status of the Slave currently
being communicated with, so communications with the Slave are always being checked.
For details on scan lists and remote I/O communications, refer to the operation manual for the
DeviceNet (Master) Unit.
Note When a scan list is disabled, communications are possible with all Slaves on the DeviceNet
Network with fixed allocations. Without scan lists, however, the DeviceNet (Master) Unit cannot
check if there is an error in a Slave.
For normal operations, always enable the scan lists.
■
Precautions
● User I/O Allocations
The user can allocate any words for Slave I/O for the DeviceNet I/O Areas (IN Area, OUT Area) in the
DeviceNet (Master) Unit.
When user allocations are used, scan lists must be created with a DeviceNet Configurator and regis-
tered in the DeviceNet (Master) Unit. The scan list is enabled as soon as it is registered, and remote
I/O communications start according to the scan list.
For details, refer to the DeviceNet Operation Manual (W267) and the DeviceNet Configurator Opera-
tion Manual (W382).
●
Fixed I/O Allocations
Slave I/O is allocated in the DeviceNet I/O area (IN Area, OUT Area) in the DeviceNet (Master) Unit
in the same order as the Slave node addresses.
When fixed allocations are used, the scan lists are automatically created and registered using the
DeviceNet (Master) Unit's software switches. The scan list is enabled as soon as it is registered, and
remote I/O communications start according to the scan list. When scan list is enabled, the mode is
called the scan list-enabled mode.
The registered scan lists can be cleared using the software switches. When scan lists are cleared
(disabled), the mode is called the scan list-disabled mode.