Rockwell Automation 1761-NET-DNI DeviceNet Interface (DNI) - Manual (Page 51)

Publication 1761-UM005B-EN-P - October 2006
DNI Configuration Parameters and Programming Notes 51
Output Buffer Overdrive (Bit 6, written by the DNI)
This bit is set (1) when Master Outputs arrive at a rate faster than the
DNI can forward the data to the DF1 device. When the Buffer
Overdrive bit is set, the output image is being overwritten before it
can be sent to the DF1 device. To resolve this, limit the data
production rate in the scanner until this bit stays clear (0).
Output Status to DF1 Device
The Output Status Byte provides the following information.
DeviceNet Node Number (Bits 0 - 5)
Whenever the DNI sets (writes) output data to the DF1 device, these
six bits contain the DeviceNet address that the DNI is assigned on
DeviceNet. If the user program needs to know what node number its
DNI is configured for, program a masked move (MVM) instruction in
the ladder logic to move the node number out of this byte. The MVM
should have:
• its destination address located in the controller’s integer file
• a masked value of 003F
• the source address should match the location identified by the
Output Word Offset parameter.
DeviceNet Valid Data (Bit 6)
The DNI sets this bit (1) to the DF1 device whenever it detects that the
DNI’s DeviceNet master is on-line/operational. The ladder logic
program in the controller should monitor this bit and take any
necessary control action.
DF1 Heartbeat (Bit 7)
The DNI writes the status of this bit to the controller, using the interval
set by the DF1 Heartbeat parameter. The DNI expects the controller to
move the status of bit 7 from the output data area to the input data
area. The easiest way to accomplish this is by programming an XIC
instruction in series with an OTE instruction as shown in the following
example.
Function Heartbeat Valid Data DeviceNet Node Number
Bit Number 7 6 5 4 3 2 1 0