Rockwell Automation 1769-SDN Compact I/O DeviceNet Scanner Module User Manual - Manual (Page 56)

56 Publication 1769-UM009E-EN-P - August 2009
Chapter 4 Automatically Configure a DeviceNet Network
Type of Connection that the Scanner Sets Up
The type of update (connection) that the scanner sets up with each device
depends on the device. The scanner chooses the first connection type that the
device supports in this order:
1. change-of-state (COS)
2. polled
3. strobed
4. cyclic at 1000 ms
The scanner tries to set up a change-of-state connection. If the device doesn’t
support change-of-state, then the scanner tries to set up a polled connection,
etc. The type of connection that the scanner sets up may not be the default for
the device.
As an option, you can allocate more memory for each device.
Consideration: Description:
The scanner sets-up communication with
any device that fits within the allocated
memory size. The scanner automatically sets up communication with those devices that fit within the
memory allocated for each address.
• For example, if you allocate 2 DINTs (8 bytes) per address, the scanner sets up
communication with any device that sends or receives 0 - 8 bytes of data.
• The scanner adds as many device as it can until it runs out of memory.
• If you give too much memory to each address, you may not have enough memory for all
your devices.
The scanner skips devices that are too large. If a device needs more memory than is allocated, the scanner skips it and does not set up
communication with it.
IMPORTANT: If the Produced data size is greater than the configured I/O allocation size,
the device is added to the scanlist with a produced size set equal to the I/O allocation size.
When this happens, an I/O connection is made with the device. But it errors and error code
#77 is displayed on the 1769-SDN for the device’s node number.
For example, if you specify 2 DINTs (8 bytes) per address but a device sends 9 bytes, the
scanner does not add the device to the scan list.
Manually editing the scan list turns off
AutoScan. If you use RSNetWorx for DeviceNet software to edit the configuration of the scanner, the
scanner turns off AutoScan. Do not turn it back on or you will clear the configuration that
you just entered.
For example, if you use RSNetWorx for DeviceNet software to manually add a device to the
scan list, the scanner turns off AutoScan. If turn on AutoScan again, the scanner clears out
the current configuration and starts over.