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Operands for Masked Compare Function
Parameter Description
Length (??) The number of DWORDs or WORDs in the two
compared strings.
DWORD: 1 Length 2,048
WORD: 1 Length 4,096
IN1
The first bit string to be compared
IN2
The second bit string to be compared
M
The bit string mask containing the ongoing
status of the compare
BIT
BIT+1=the bit number where the next
comparison starts
Q
The output copy of the compare mask bit string All except constants
BN
The number of the bit where the latest
miscompare occurred, or the highest bit
number in the inputs if no miscompare
occurred
MC
Can be used to determine if a miscompare has
occurred.
Masked Compare Example 1
When %I00001 is set, MASK_COMP_WORD compares the bits
represented by the reference VALUES against the bits represented
by the reference EXPECT. Comparison begins at BITNUM+1. If an
unmasked miscompare is detected, the comparison stops. The
corresponding bit is set in the mask RESULT. BITNUM is updated to
contain the bit number of the miscompared bit. In addition, the
output string NEWVALS is updated with the new value of RESULT,
and coil %Q00002 is turned on. Coil %Q00001 is turned on
whenever MASK_COMP_WORD receives power flow.
GFK-2950C
Chapter 4. Ladder Diagram (LD) Programming
Allowed Operands
Constant
All. Constants are legal only when
Length is 1
All. Constants are legal only when
Length is 1
All except flow or variables in %S
memory. Constants are legal only
when Length is 1
All except variables in %S - %SC
memories
All except constants and variables in
%S memory
flow
February 2018
Optional
No
No
No
No
No
No
No
Yes
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