Devicenet (Mcw151-Drt-E Only); Remote I/O Communications - Omron R88A-MCW151-DRT-E Operation Manual

DeviceNet (MCW151-DRT-E only)

4-2

DeviceNet (MCW151-DRT-E only)

Accessing MC Unit
memory through remote
I/O areas
Accessing MC Unit
memory with Explicit
Message Communications
4-2-1

Remote I/O Communications

68
The MCW151-DRT-E is connected to the DeviceNet network as a DeviceNet
Slave. This allows data from any area in the MC Unit to be read or written
from the Master. Through the DeviceNet, the MC Unit memory can be
accessed using one of the following two methods.
Remote I/O communication enables automatic exchange of I/O data between
the MC Unit and a PC with DeviceNet Master Unit without special program-
ming in the PC. For the MC Unit, the input and output areas can each contain
up to 4 words.
Once the MC Unit's memory input and output areas have been set, the MC
Unit memory can be read and written. The input area is regularly read by the
Master and the output is regularly written from the Master. This process main-
tains consistency between the Slave's input and output areas and the input
and output areas allocated to the Master.
The data is transferred automatically at high speed so it is useful to use this
for data which requires regular data transfers with the Master.
When larger amount of data needs to be exchanged with the MC Unit, explicit
message communications can be used.
Transferring data with explicit message communications takes more time than
transferring data with the input and output areas, but all of the MC Unit mem-
ory can be accessed.
Use this feature for large data transfers which can be performed when
required, such as transferring position profile data.
MC Unit
Input Area
Output Area
VR memory
Table memory
Refer to Appendix B Device Protocol (MCW151-DRT-E only) for the Device
Protocol definition.
The Master and Slaves can communicate as described below with DeviceNet
remote I/O communications.
• Input Area:
Inputs at the Slave are read automatically and mirrored in the Master's
input area.
• Output Area:
Data written in the output area allocated in the Master's memory are auto-
matically output to the corresponding Slave.
Remote I/O
communications
Explicit message com-
munications (Transfers
data in any area)
DeviceNet Network
Section 4-2
Master Unit
CPU Unit