Rockwell Automation 1771ACN/B_1771ACNR/B,D17716.5.123 U.MNL CONTROLNET ADAPTER - Manual (Page 40)

Planning to Use Your ControlNet Adapter Module 4–4
Publication 1771-6.5.123 – May 1996
Mapping Directly Into Processor Memory
ControlNet also allows mapping 1771 nondiscrete I/O modules
directly into processor memory. This eliminates the need for
programming CIO or other transfer instructions in your ladder
program. When you map a nondiscrete I/O module, the processor
opens a connection to the adapter. Data is produced and/or consumed
over the network, continuously and asynchronous to the ladder logic
program scan. At the adapter, nondiscrete transfers are initiated to
the module in its resident chassis asynchronous to the network
activity. Once configured, these data transfers are active in all
processor modes (RUN, PROG, and TEST).
Example: Nondiscrete Input Module Communications
0 1 2 3 4 5 6 7
PLC-5/40C
0 1 2 3 4 5 6 7
1771-IXHR 1771 8 Point In 1771-P4S Empty
Nondiscrete Input Module
1
4
2
3
1. The processor opens a connection to the adapter for consuming
the data from the nondiscrete module. The processor requests the
adapter to produce the module’s data at the Actual Network
Packet Time shown in the configuration.
2. Upon receiving the request, the adapter starts initiating
continuous read requests to the module. This occurs
asynchronous to any activity on the network.
3. The module processes the read requests and responds to the
adapter as fast as it can.
4. The adapter produces the most recently received copy of the
module’s data on the network at the Actual Network Packet Time.
Note: If the nondiscrete input module can only respond to read
requests every 50ms, and you set your update time to 10ms, the
adapter will be sending 5 copies of each data block.
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