Reference MVI56-DH485R
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ControlLogix Platform
User Manual
DH485 Interface Module for Remote Chassis
ProSoft Technology, Inc.
Page 59 of 97
August 27, 2009
The following illustration shows the layout of the database.
Module’s Internal Database Structure
4000 registers for user data
0
Register Data
3999
Data contained in this database is paged through the input and output images by
coordination of the ControlLogix ladder logic and the MVI56-DH485R module's
program. Up to 42 words of data can be transferred from the module to the
processor at a time. Up to 42 words of data can be transferred from the
processor to the module. The read and write block identification codes in each
data block determine the function to be performed or the content of the data
block. The module uses the following block numbers:
Block Range
Descriptions
0 to -1
Status Blocks
1 to 100
Read or write data
1000 to 1099
Read data initialization blocks
3000
Port 0 command disable block
3001
Port 0 command enable block
3002
Port 0 command conditional block
3100
Port 1 command disable block
3101
Port 1 command enable block
3102
Port 1 command conditional block
9998
Warm-boot control block
9999
Cold-boot control block
Each image has a defined structure depending on the data content and the
function of the data transfer.
Normal Data Transfer
Normal data transfer includes the transferring of data received by, or to be
transmitted to, the DH-485 drivers and the status data. This data is transferred
through read (input image) and write (output image) blocks. Refer to Module
Configuration for a description of the data objects used with the blocks and the
ladder logic required. The following topics discuss the structure and function of
each block.
