Read and write block transfer sequences – ProSoft Technology MVI69L-MBTCP User Manual
Page 70
Backplane Data Exchange
MVI69L-MBTCP ♦ CompactLogix Platform
User Manual
Communication Module
Page 70 of 152
ProSoft Technology, Inc.
January 6, 2014
4.2.3 Read and Write Block Transfer Sequences
There are 240 words of data transferred per block along the backplane between
the module and the processor.
The Write Block ID associated with the block requests data from the processor.
Under normal program operation, the module sequentially sends read blocks and
requests write blocks. The application uses one read and one write block, the
sequence is as follows:
R1W1
R1W1
R1W1
R1W1
…
This sequence continues until interrupted by other write block numbers sent by
the controller or by a command request from a node on the Modbus network or
operator control through the module’s Ethernet port.
The backplane communication is configured as follows:
Database address 0 to 239 is continuously transferred from the module to the
processor. Database address 240 to 479 is continuously transferred from the
processor to the module.