VCVT instruction in ARM M4-F

Hi all, ARM community!

I am dealing with a Arm Cortex M4-F with Floating Point Unit and I need to carry out a floating point to fixed point conversion. In accordance with what I read in the Arm Keil website at the link: https://www.keil.com/support/man/docs/armasm/armasm_dom1361289951363.htm it could be possible to use the assembly instruction "VCVT{cond}.S32.F32 Sd, Sd, #fbits" to make the conversion I need. I have been using the compiler v5 and v6.  

Unfortunately I am not able to compile this instruction! I can compile the VCVT floating point to integer but not this one (floating point to fixed point).

Does anyone know the the reason? Have you ever used this instruction (floating point to fixed point) in a Cortex M-4 with FPU?

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