Installation guide

70 Estimating Network Performance
890 USE 100 00
3.6 Reading and W riting with the MSTR
The MSTR instruction is a ladder logic function that provides access to
the Modbus Plus network. Its format is shown in Figure 30.
ENABLE
ABORT
ACTIVE
ERROR
COMPLETE
MSTR
CONTROL BLOCK
DATA AREA START
DATA AREA SIZE
(4XXXX)
(4XXXX)
(N)
SUMMARY OF MSTR OPERATIONS
1 WRITE
2 READ
3 GET LOCAL STATISTICS
4 CLEAR LOCAL STATISTICS
5 WRITE GLOBAL DATABASE
6 READ GLOBAL DATABASE
7 GET REMOTE STATISTICS
8 CLEAR REMOTE STATISTICS
9 PEER COP HEALTH
Figure 30 MSTR Function Format
A complete description of how you can program your application using
the MSTR is provided in the Modicon Ladder Logic Block Library User
Guide (840 USE 101 00)). This overview will assist you in following the
sample communication on the next page.
The Control Block is a 4x reference that is the starting register in a
block of nine consecutive registers. These registers define the intended
actions and Modbus Plus routing for the communication. Their
contents are unique for each type of operation.