Rockwell Automation 1785-Lx0C15 ControlNet PLC-5 Programmable Controllers User Manual - Manual (Page 42)

1785-UM022C-EN-P - February 2008
2-4 Planning to Use Your ControlNet PLC-5 Processor
The following scheduled data-transfer operations are supported by the
ControlNet processors on a ControlNet network:
Table 2.A ControlNet Scheduled Data-Transfer Operations
Unscheduled Data-Transfer Operations on a ControlNet Network
The ControlNet network allows you to use unscheduled messaging
when deterministic delivery is not required. Unscheduled operations
include:
• unscheduled I/O data transfers, or when unscheduled messaging
is event-driven—through ControlNet I/O Transfer (CIO)
instructions
• peer-to-peer messaging—through Message (MSG) instructions
• messaging from programming devices
• messaging from Human Machine Interface (HMI) devices
Operation Description
Discrete I/O Data
Transfer (can be done
as a rack or module
connection) Performed in a deterministic and repeatable manner
asynchronous to and independent of the ladder-logic
program scan. You configure all ControlNet discrete I/O
data transfers on a per-node basis in the I/O map table
(scanlist configuration). 1
Non-discrete I/O Data
Transfer (can be done
as a module
connection)
Handled with the same priority as discrete I/O data
transfer. You can update analog data without using
block-transfer instructions in ladder programs. You do
this by including non-discrete I/O data-transfer
configurations in the I/O map table (scanlist
configuration). This data is updated in the buffers and
data-table files between logic scans in the same
manner as that used in discrete I/O data transfer.
1
Peer-to-peer
Communication Allows a ControlNet processor to communicate with
any other ControlNet processor on the ControlNet
network with the same priority as that of the discrete
and non-discrete I/O data transfers discussed above.
1
1 While scheduled data transfer is asynchronous to program scanning, all data is
presented synchronously to and from the user data table during housekeeping.