Specifications

App - 85
Appendix 9.2 Cyclic transmission
The link scan of MELSECNET/H and the sequence scan of the PLC operate
asynchronously. Thus, the link refresh executed per sequence scan is asynchronous
with the link scan.
Depending on the timing of the link refresh, the link data with data types of more than 32
bits (two words), such as the ones below, may be broken up into new and old data.
• Floating point data
• Current values of positioning module, command speed.
The MELSECNET/H provides the following functions for making handling of the link data
easy.
• 32-bit data guarantee........................................ Appendix 9.2.1
• Block guarantee of cyclic data per station ....... Appendix 9.2.2
When the conditions (32-bit data guarantee execution conditions) are not met, the
program should be interlocked by seeing the example in Appendix 9.2.3.
Appendix 9.2.1 32-bit data guarantee
32-bit data precision is guaranteed automatically by setting parameters so that the
following conditions 1) to 4) are satisfied.
If conditions 1) to 4) are not satisfied, a warning for 32-bit data separation is displayed
during setting with a peripheral device.
1) The start device number of LB is a multiple of 20
H.
2) The number of assigned LB points per station is a multiple of 20
H.
3) The start device number of LW is a multiple of 2.
4) The number of assigned LW points per station is a multiple of 2.
Parameter settings for network assignment ranges
4)4) 2)2) 1) 3) 1) 3)
For the send data of less than 32 bits, an interlocked program is not required if the above
conditions are satisfied.
QCPU QJ71
BR11
I/O
QCPU QJ71
BR11
I/O
Positioning
QCPU QJ71
BR11
I/O
Positioning
Floating point
Current values, command speed, 32-bit I/O data, etc.
MELSECNET/H
POINT
When handling data larger than 32 bits (two words), enable the block guarantee per
station described in Appendix 9.2.2, or apply interlocks in the programs by seeing the
interlock program example in Appendix 9.2.3.