ProSoft Technology MVI71-DNP - Manual (Page 85)

Reference MVI71-DNP ♦ PLC Platform
DNP 3.0 Master/Slave Communication Module
ProSoft Technology, Inc. Page 85 of 172
August 23, 2007
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.
Block 9958 or 258 – PLC Binary Input Event
If the PLC sends a block 9958, the module will place the binary input event data
in the block into the event buffer and alter the data values for the points in the
DNP binary input database. The format for the event message is shown in the
following table.
Word Offset in Block Data Field(s) Description
0 Block ID This field contains the value of 9958 identifying the
event block to the module.
1 Event Count This field contains the number of events contained in
the block. Valid values for this field are 1 to 12.
2 Sequence
Counter This field holds the sequence counter for each 9958
block transfer. This synchronizes and confirms
receipt of the block by the module.
3 DNP Binary Input
Data point This is the data point in the DNP binary input
database represented by the event.
4 Month/Day/State Formatted: bits 0 to 4 = Day, bits 8 to 11 = Month, bit
15 = digital state for point. All other bits are ignored.