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Appendix A
DeviceNet Overview
© National Instruments Corporation
A-11
Figure A-5 shows an example of four COS/cyclic I/O connections.
Figure A-5. COS/Cyclic I/O Example
Assembly Objects
One of the more important objects in the DeviceNet Specification is the
Assembly Object. There are two types of Assembly Object: input
assemblies and output assemblies. Assembly objects act like a switchboard,
routing incoming and outgoing data to its proper location within the device.
Output assemblies receive an output message from an I/O connection and
distribute its contents to multiple attributes within the slave. Input
assemblies gather multiple attributes within the slave for transmission on
an I/O connection.
Assembly Object. There are two types of Assembly Object: input
assemblies and output assemblies. Assembly objects act like a switchboard,
routing incoming and outgoing data to its proper location within the device.
Output assemblies receive an output message from an I/O connection and
distribute its contents to multiple attributes within the slave. Input
assemblies gather multiple attributes within the slave for transmission on
an I/O connection.
Figure A-6 shows the operation of input and output assemblies.
Master
MAC ID = 1
Slave
MAC ID = 9
Slave
MAC ID = 11
Slave
MAC ID = 12
Slave
MAC ID = 13
COS ACK to Slave
6 Byte COS
to Slave
EPR = 400 ms,
no ACK
4 Byte COS to Master
EPR = 200 ms
2 Byte Cyclic to Master
EPR = 500 ms, no ACK
Cyclic ACK
to Master
12 Byte Cyclic
to Slave
EPR = 100 ms
Output data
Input data