Convert function
- Thread starter zezito
- Start date
Peter Nachtwey
Member
ROUND, TRUNC
hello zezito;
Analysing basic math functions can be rewarding at times; however, if you just look at the S7-200 online help for the functions "round" and "trunc" you will find that they transform a Real variable into a DINT variable, in 2 slightly different ways.
Hope this helps,
Daniel Chartier
Analysing basic math functions can be rewarding at times; however, if you just look at the S7-200 online help for the functions "round" and "trunc" you will find that they transform a Real variable into a DINT variable, in 2 slightly different ways.
Hope this helps,
Daniel Chartier
rdrast
Lifetime Supporting Member
some_REAL = 176.565
l some_REAL
RND
T ROUNDED_DINT // ROUNDED_DINT = 177 (Fractional part rounded up)
L some_REAL
TRUNC
T TRUNCATED_DINT //TRUNCATED_DINT = 176 (fractional part stripped)
An example basic FC I use in S7 is this one:
I use that to go from Reals to Int's, while safely preserving the sign. Without range checking, you could pass a real value of say 128,382, which would give unexpected results when converted to an integer.
Your milage may vary.
l some_REAL
RND
T ROUNDED_DINT // ROUNDED_DINT = 177 (Fractional part rounded up)
L some_REAL
TRUNC
T TRUNCATED_DINT //TRUNCATED_DINT = 176 (fractional part stripped)
An example basic FC I use in S7 is this one:
L #REAL_In // Load acc with input real
RND // Round to nearest double int, store in ACCUM1
T #TmpDI // store copy for later
// Declares:
// in REAL_In REAL Input Value to convert
// out INT_Out INT Signed result of conversion
// out bValid BOOL True if conversion was valid
// temp TmpDI DINT Temporary working double int
AD DW#16#FFFF8000 // Create a mask for bits 15-31
JZ good // if all bits are clear, number is positive and valid.
XOD DW#16#FFFF8000 // else, if all bits set, number is negative and valid
JZ good // If result is not zero, then at least one bad bit detected.
R #bValid // Validity check failed, reset vailid status
L W#16#0 // and for the hell of it, reset the output word to zero.
T #INT_Out
BE
good: S #bValid // Set conversion valid flag (Ok, assume it will be valid)
L #TmpDI // Result was zero, so move low word
AD DW#16#FFFF // mask off high word for hell of it
T #INT_Out // to ouput word,
BE
I use that to go from Reals to Int's, while safely preserving the sign. Without range checking, you could pass a real value of say 128,382, which would give unexpected results when converted to an integer.
Your milage may vary.
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