Precision Correction On Comparison Errors (Trunc) - Siemens SINUMERIK 840D sl Programming Manual

Flexible NC programming
1.7 Comparison and logical operations
Example: relational operators
IF R10>=100 GOTOF DEST
or
R11=R10>=100
IF R11 GOTOF DEST
The result of the R10>=100 comparison is first buffered in R11.
Example: logic operators
IF (R10<50) AND ($AA_IM[X]>=17.5) GOTOF DESTINATION
or
IF NOT R10 GOTOB START
NOT is only applied to one operand.
Example: bit logic operators
IF $MC_RESET_MODE_MASK B_AND 'B10000' GOTOF ACT_PLANE
1.7.1

Precision correction on comparison errors (TRUNC)

Function
The TRUNC command truncates the operand multiplied by a precision factor.
Settable precision for comparison commands
Program data of type REAL are displayed internally with 64 bits in IEEE format. This display
format can cause decimal numbers to be displayed imprecisely and lead to unexpected
results when compared with the ideally calculated values.
Relative equality
To prevent the imprecision caused by the display format from interfering with program flow,
the comparison commands do not check for absolute equality but for relative equality.
Programming
Precision correction on comparison errors
TRUNC (R1*1000)
1-22
Programming Manual, 03/2006 Edition, 6FC5398-2BP10-1BA0
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