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5 Function blocks
5.3 BC, data block comparator
144
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Inputs
The marker ranges corresponding to the start addresses specified on inputs
I1 and I2 are compared with each other.
The function block inputs I1, I2 and NO can have the following operands:
•
Constant.
•
Markers MD, MW, MB.
•
Analog inputs IA01 to IA04:
•
IA01: Terminal I7.
•
IA02: Terminal I8.
•
IA03: Terminal I11.
•
IA04: Terminal I12.
•
Analog output QA01.
•
Output
QV of a different function block
...
Specifying the marker range
Marker ranges can be specified with or without an offset.
Marker range without offset
If MB, MW or MD markers are specified at both I1 and I2 the number of the
markers is the start of comparison range.
Marker range with offset
If you wish to work with an offset, specify one of the following variables at
function block input I1 or I2:
•
Analog input IA..,
•
Analog output QA..,
•
Constant.
•
Output ..QV> of a function block.
The value at the input is taken as the offset to marker byte MB01.
Example:
A value 0 at input I1 means that the reference data block for the comparison
starts at MB01. A value 100 at I2 means that the destination data block for
the comparison starts at MB101.
￫
The offset definition enables you to address the marker ranges
(e.g. MB380) that you cannot address when using marker
operands (direct addressing).
Offset calculation for addressing marker words:
Offset = MW (x - 1) x 2
Offset calculation for addressing marker double words:
Offset = MD (x - 1) x 4
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