Scan List Enabled And Scan List Disabled - Omron CJ1W-DRM21 Operation Manual

4 Remote I/O Master Communications
Creating the Scan List
The way that a scan list is prepared varies with the allocation method as shown below.
Allocations
How to create scan list
Precautions for Safe Use
• Be sure to create a scan list before you start actual system operation.
• It is still possible to communicate with Units (with the scan list disabled) if a scan list is not cre-
ated when fixed allocations areas 1 to 3 are used. This may result in faulty operation because
the Master Unit will communicate with slaves even if they do not start up due to errors, such as
equipment failure if there is no scan list.
4-2-2

Scan List Enabled and Scan List Disabled

The scan list must be made. The scan list modes are described here.
Scan List Enabled (Used for Actual Operation)
Remote I/O communications are performed according to the registered scan list and only with slaves
that are on the list. A Verification Error occurs (*_Mstr1VefyErr changes to TRUE) if a slave regis-
tered on the scan list is not present on the network, if a slave did not start up when remote I/O com-
munications started, or if the number of I/O points did not match the number registered.
Scan List Disabled (Used when Changing System Configuration)
You can perform remote I/O communications with fixed allocations instead of a scan list in order to
change a system configuration. Do not operate without a scan list during actual system operation.
Use this mode only to replace a Master Unit or to change system configuration (change a connected
slave or a node address).
Note 1 To disable the scan list, change *_Sw1SListClrCmd (Scan List Clear Switch) to TRUE dur-
ing remote I/O communications with the scan list enabled (with fixed allocations, user-set
allocations using device variable for CJ-series Unit, or user-set allocations using the CX-
Integrator). In all these cases, remote I/O communications are executed using the fixed
allocations area that was last used when the list was disabled.
2 Slaves that are connected to the network while communications are in progress are also
targeted for communications. Errors cannot be confirmed, however, even if there are slaves
present that did start up due to errors because there is no scan list available to check com-
munications against. The communications cycle time will also be significantly longer than
the calculated value.
4-12
Fixed allocations
With the CPU Unit in PRO-
GRAM mode:
1. Change the one of the
Fixed Allocated
Switches (1 to 3) to
TRUE.
2. Change the Scan List
Enable Switch to
TRUE.
CJ-series DeviceNet Units Operation Manual for NJ-series CPU Unit(W497)
User-set allocations
using device variable for
CJ-series Unit
With the CPU Unit in PRO-
GRAM mode.
1. Change the Master
User-set Allocations
Setup Switch to TRUE.
User-set allocations
from the CX-Integrator
Create a list from the CX-
Integrator. (Acquire a list
of online devices, use it to
create a scan list, and
then register the scan list
in the Master Unit.)