ProSoft Technology InRax MVI71-DNPSNET, Руководство пользователя

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MVI71-DNPSNET ♦ PLC Platform Reference
Distributed Network Protocol Interface Module
Page 54 of 100 ProSoft Technology, Inc.
September 22, 2008
Read Block
These blocks of data transfer information from the module to the PLC processor.
The structure of the BTR image used to transfer this data is shown in the
following table.
Block Offset Content
0 Read block ID
1 Write block ID
2 to 61 Read data
62 to 63 Spare (Not used)
The Read Block ID is an index value used to determine the location of where the
data will be placed in the PLC processor user data file. Each transfer can move
up to 60 words (block offsets 2 to 61) of data.
The Write Block ID associated with the block requests data from the PLC
processor. Under normal, program operation, the module sequentially sends
read blocks and requests write blocks. For example, if two blocks of read data
and three blocks of write data are to be moved between the module and the
processor, the sequence will be as follows:
R1W1 R2W2 R1W3 R2W1 R1W2 R2W3 R1W1
This sequence will continue until interrupted by other write block numbers sent by
the controller or by a command request from a node on the DNP network or
operator control through the module's Configuration/Debug port.
Write Block
These blocks of data transfer information from the PLC processor to the module.
The structure of the BTW image used to transfer this data is shown in the
following table.
Block Offset Content
0 Write block ID
1 to 60 Write data
61 to 63 Spare (Not used)
The Write Block ID is an index value used to determine the location in the
module's database where the data will be placed. Each transfer can move up to
60 words (block offsets 1 to 60) of data.
Command Control Blocks
Command control blocks are special blocks used to control the module or
request special data from the module. The current version of the software
supports several command control blocks each of which is discussed in the
following topics.