ProSoft Technology InRax MVI71-DNPSNET, Руководство пользователя

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MVI71-DNPSNET ♦ PLC Platform Reference
Distributed Network Protocol Interface Module
Page 80 of 100 ProSoft Technology, Inc.
September 22, 2008
Data Transfer Interface
Data is transferred between the PLC processor and the module using module's
BTR/BTW images when the block-transfer interface is employed or directly from
user data files to the module when the side-connect interface is utilized. Each
BTR/BTW block transfer operation transfers up to 64 words of information of
which 60 holds data. The module defines the blocks to be transferred between
the PLC and the module when the system is initialized. For the PLC BTR
operations, word 0 of the module's BTR 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 BTW 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 shown in the following table.
DATA AREA Cfg Points Words Offset
BINARY
INPUTS 2 32 2 0 to 1
ANALOG
INPUTS 148 148 148 2 to 149
COUNTER
DATA
25 25 50 150 to 199
BINARY
OUTPUTS 4 64 4 200 to 203
DNP DATA
ANALOG
OUTPUTS 52 52 52 204 to 255
For the example above, 200 registers will be transferred from the processor
(requires 4 BTW blocks) and 56 registers will be transferred to the processor
(requires 1 BTR block). The data transfer parameters should be defined as
follows:
Parameter Value
Write Register Start 0
Write Register Count 200
Read Register Start 200
Read Register Count 56
Note that in one block, one or more DNP data types may be transferred. This is
especially important when considering the counter data. Counter values require
two registers to store their value. The value of a counter should never be passed
in two separate blocks. To avoid this potential problem, always configure the
module to have the counter data start on an even word number.