Help Me! Real To Dint In Step7

nandao · Feb 21, 2006

Hi, can anyone show me how to convert from a Real to an DInt in Step7?
I have a md400 (real) with valor max. 150000.0 and i need convert to DINT to show in a HMI...
I am using LAD...

I have seen DI_R but, where is the oposite function R_DI?

Thanks!

S7Guy · Feb 21, 2006

Open up the Siemens help and look for TRUNC. That will get you going again.

rdrast · Feb 21, 2006

Just an aside...
But I've always hated the fact that S5/S7 could cast to a more complex type in a single instruction, but can't cast down without a LOT of work.

S7Guy · Feb 21, 2006

rdrast said:
Just an aside...
But I've always hated the fact that S5/S7 could cast to a more complex type in a single instruction, but can't cast down without a LOT of work.

I don't quite get that. It takes the same number of instructions to convert numbers in both directions. Or maybe I don't quite understand what you mean by cast.

jacekd · Feb 22, 2006

Nandao, in fact you have more possibilities, in LAD there're :

TRUNC - rounding towards zero
ROUND - rounding to the nearest dint
CEIL - rounding towards +infinity
FLOOR - rounding towards -infinity

Hopefully I made enough mess in your brain

.

nandao · Feb 22, 2006

but are round and trunc limit in 32768? I need to convert 150000.0 ...

nandao · Feb 22, 2006

jacekd said:
Nandao, in fact you have more possibilities, in LAD there're :

TRUNC - rounding towards zero
ROUND - rounding to the nearest dint
CEIL - rounding towards +infinity
FLOOR - rounding towards -infinity

Hopefully I made enough mess in your brain .

but are round and trunc limit in 32768? I need to convert 150000.0 ...

nandao · Feb 22, 2006

S7Guy said:
I don't quite get that. It takes the same number of instructions to convert numbers in both directions. Or maybe I don't quite understand what you mean by cast.

but are round and trunc limit in 32768? I need to convert 150000.0 ...

SimonGoldsworthy · Feb 22, 2006

From the ladder editor, click on Help>Help On STL and then type in the instruction. For example the help on RND is below:

RND (conversion of a 32-bit IEEE floating-point number to 32-bit integer) interprets the contents of ACCU 1 as a 32-bit IEEE floating-point number (32-bit, IEEE-FP). The instruction converts the 32-bit IEEE floating-point number to a 32-bit integer (double integer) and rounds the result to the nearest whole number. If the fractional part of the converted number is midway between an even and an odd result, the instruction chooses the even result. If the number is out of the permissible range, then the status bits OV and OS are set to 1. The result is stored in accumulator 1.
Conversion is not performed and an overflow indicated in the event of a fault (utilization of a NaN or a floating-point number that cannot be represented as a 32-bit integer number).

jacekd · Feb 22, 2006

nandao said:
but are round and trunc limit in 32768? I need to convert 150000.0 ...

No, they aren't. Result of conversion is limited to dint span. Check your code. Or post it, so we can do it for you.

nandao · Feb 22, 2006

SimonGoldsworthy said:
From the ladder editor, click on Help>Help On STL and then type in the instruction. For example the help on RND is below:

RND (conversion of a 32-bit IEEE floating-point number to 32-bit integer) interprets the contents of ACCU 1 as a 32-bit IEEE floating-point number (32-bit, IEEE-FP). The instruction converts the 32-bit IEEE floating-point number to a 32-bit integer (double integer) and rounds the result to the nearest whole number. If the fractional part of the converted number is midway between an even and an odd result, the instruction chooses the even result. If the number is out of the permissible range, then the status bits OV and OS are set to 1. The result is stored in accumulator 1.
Conversion is not performed and an overflow indicated in the event of a fault (utilization of a NaN or a floating-point number that cannot be represented as a 32-bit integer number).

I have seen this on Help, but i have listened that there are problems with valors above 32768, and i don´t have a CPU here now fot test...

SimonGoldsworthy · Feb 22, 2006

Who reported these problems with values above 32768 ? What are the specifics ? First I've heard of it (I use 318/317 CPU's)

S7Guy · Feb 22, 2006

The help contents are correct. These instructions work with double integers.

nandao · Feb 22, 2006

SimonGoldsworthy said:
Who reported these problems with values above 32768 ? What are the specifics ? First I've heard of it (I use 318/317 CPU's)

Help desk of Siemens in Brazil. I found very stranger this, exactly for having seen the help, and there it did not say nothing on this. It was then that I found the site and I decided to ask for helps vcs specialists.

Ken M · Feb 22, 2006

What did Siemens Brazil tell you?
What are these 'problems'?
Are you sure they were answering the question you thought you were asking?

Ken

Help Me! Real To Dint In Step7

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