ProSoft Technology MVI69-DNPSNET - Manual (Page 82)

MVI69-DNPSNET ♦ CompactLogix or MicroLogix Platform Reference
Distributed Network Protocol Interface Module
Page 82 of 119 ProSoft Technology, Inc.
November 3, 2008
Output data is sourced from the controlling master station and passed to the
processor over backplane from the module. These data are used in the ladder
logic to control operations and I/O in the processor.
Data Transfer Interface
Data is transferred between the CompactLogix or MicroLogix processor and the
module using module's I/O images. Each block transfer operation transfers up to
a maximum of 240 words of data if Block size of 240 is used. The other words in
the block contain block header identification codes, or not used. The module
defines the blocks to be transferred between the PLC and the module when the
system is initialized. For the PLC read operations, word 0 of the module's input
image identifies the data set contained in the image. Word 1 contains the block
index the module is requesting the processor to write. The PLC constructs the
write image to send to the module in the module's output image. The first word of
the block identifies the data set contained in the block.
The module determines the block numbers required based on the module read
and write register counts defined in the configuration file. The user is responsible
for defining these parameters and the starting location of these data areas in the
module's database correctly. These data must correspond to the DNP database
definitions defined. The module stores the data in fixed order for the data types.
The size of each data area for each type is determined by the user configuration.
An example is given in the following table.
DATA AREA Cfg Points Words Offset
BINARY
INPUTS 2 32 2 0 to 1
ANALOG
INPUTS 48 48 48 2 to 49
FLOAT INPUTS 10 10 20 50 to 69
COUNTER
DATA 25 25 50 70 to 119
BINARY
OUTPUTS 4 64 4 120 to 123
ANALOG
OUTPUTS 52 52 52 124 to 175
DNP DATA
FLOAT
OUTPUTS 20 20 40 176 to 215
For the example above, 120 registers will be transferred from the processor (all
the input data) and 96 registers will be transferred to the processor (all the output
data). The data transfer parameters should be defined as follows:
Parameter Value
Write Register Start: 120
Write Register Count: 96
Read Register Start: 0
Read Register Count: 120
The configuration above will require one block to read and one block to write all
the DNP data between the module and the processor.