ProSoft Technology MVI94-DNP - Manual (Page 82)

Reference MVI94-DNP ♦ Flex I/O
User Manual DNP 3.0 Server over Ethernet Communication Module
Page 82 of 131 ProSoft Technology, Inc.
December 17, 2010
6 Next the ladder logic examines the value of the write_block_code and
determines the data type and offset into the data type data table where the
data will be sourced.
7 The required six-word, write data is copied to the module’s output image
(words 1 to 6). To "trigger" the transfer operation, the ladder logic moves the
write_block_code into word 0 of the output image.
8 The module’s program recognizes the new write_block_code. It transfers the
data to the correct offset in the database using the block number provided.
9 The module sets the last_write_block_code to the value of write_block_code.
10 The module now selects the next read and write blocks. The data for the
processor read operation is placed in the input image and the
write_block_code is set in word 1. The module "triggers" the transfer
operation by setting the new read_block_code in word 0 of the input image.
11 The sequence continues at step 3.
The previous discussion is for normal data transfer operation. The following table
lists the block identification codes used by the module for data transfer.
Data Type Start Block # Max Block # Max # Of Points Type
Digital Input 0 9 960 Slave
Digital Output 20 29 960
Counters 40 49 30
Analog Input 60 79 120
Float Input 300 319 60
Double Input 320 349 30
Analog Output 80 89 60
Float Output 400 419 60
Double Output 420 449 30
IED Digital Input 100 109 960 Master
IED Digital Output 120 129 960
IED Counters 140 149 30
IED Analog Input 160 179 120
IED Analog Output 180 189 60
Data is transferred between the processor and the module using the block
identification codes of 0 to 189, 300 to 349 and 400 to 449. Other block codes
control the module from the processor’s ladder logic. They are implemented
when the ladder logic needs to control the module. In order to use one of the
blocks, the ladder logic inserts the data and code in the output image of the
module. The data should be set before the code is placed in the block. This
operation should be performed after the receipt of a new write block from the
module.