ProSoft Technology MVI56-104S - Manual (Page 67)

Ladder Logic MVI56-104S ♦ ControlLogix Platform
User Manual IEC 60870-5-104 Server Communication Module
ProSoft Technology, Inc.
Page 67 of 188
November 18, 2009
3.2.2 Write Block
This block transfers IEC input (monitor) data to be sent to the remote IEC 104
Client through the module from the ControlLogix processor. The following table
outlines the structure of data contained in the output image of a normal Write
Block.
Offset Description Length
0 Write Block ID 1
1 to 200 Write Data 200
201 to 247 Spare 47
The Write Block ID is sent in the Read Block as an index value used by the
ladder logic to determine where the current 200-word block of output data should
be taken from the ControlLogix processor IEC870S.WriteData controller tag
array. Each output data block transfer can move up to 200 words of user
application data (Write Block offsets 1-200) from the processor to the module.
During normal operation, the module sequentially sends Read Blocks and
requests Write Blocks. For example, if the application uses three read and two
write blocks, the sequence will be as follows:
R1W1
→R2W2→R3W1→R1W2→R2W1→R3W2→R1W1→
This sequence will continue until interrupted by special function write block
numbers sent by the controller or operator control through the module’s
Configuration/Debug port.
3.3 Special Function Blocks
Special Function Blocks are used to provide optional module functions. The
current version of the software supports seven special function blocks:
1 Output Data Initialization
2 Event Messages using GMT Time
3 Event Messages using UTC Time
4 Read Module's Time into Processor
5 Write Processor's Time out to Module
6 Warm Boot
7 Cold Boot