2
\$\begingroup\$

When assembling the code, I get the error : fpu.s(13): error: A1240E: Immediate value cannot be used with this operation

AREA PGRM, CODE, READONLY
ENTRY
EXPORT __main
__main
    LDR R0,=0XE000ED88
    LDR R1,[R0]
    ORR R1,R1,#(0xF << 20)
    STR R1,[R0]
    dsb



    VMOV.F32 S7, #0x419c0000
    VMOV.F32 S8, #0X41B40000
    VADD.F32 S9,S7,S8

LOOP    B LOOP
    END
\$\endgroup\$
  • 2
    \$\begingroup\$ I consider this question as off-topic, because is solely programming related, no matter what platform is used. \$\endgroup\$ – Ariser May 8 '18 at 7:28
  • \$\begingroup\$ Be consistent with your hexadecimal numbers. Use #0xFFFFFFFF instead of sometimes using #0XFFFFFFFF. You can confuse the compiler with being inconsistent. \$\endgroup\$ – Sparky256 May 8 '18 at 7:42
  • \$\begingroup\$ @Sparky256, the compiler will get confused? I thought it either rejects completely or accepts syntax for constants and those look legal enough. \$\endgroup\$ – TonyM May 8 '18 at 9:38
2
\$\begingroup\$

In VMOV, the F32 format expects the following argument as immediate value:

Any number that can be expressed as \$\pm n \times 2^{–r}\$, where n and r are integers, 16 <= n <= 31, 0 <= r <= 7.

You have the following immediate values:

$$ \text{0x}419C0000 = 4199\times2^{18} \\ n = 4199 \quad r = -18 $$ and $$ \text{0x}41B40000 = 4205\times2^{18} \\ n = 4205\quad r = -18 $$

In both instructions, the immediate values are clearly out of the expected range. You should scale these parameters beforehand.

\$\endgroup\$
  • \$\begingroup\$ This was my thought too, but checking the user guide for the cortex-m4 this restriction isn't listed. infocenter.arm.com/help/index.jsp?topic=/com.arm.doc.dui0553a/… \$\endgroup\$ – Colin May 8 '18 at 7:37
  • \$\begingroup\$ @Colin__s Not sure I follow, the same description of value ranges is there in the link you presented. Do you mean to say the assembler should turn a blind eye to this? \$\endgroup\$ – Vicente Cunha May 8 '18 at 7:43
  • \$\begingroup\$ please check the link again, I had the wrong thing on my clipboard when I first commented. The cortex m4 manual states "Restrictions There are no restrictions." \$\endgroup\$ – Colin May 8 '18 at 7:46
  • \$\begingroup\$ @Colin__s Indeed, this seems the case. If value ranges are not to blame, my next guess would be wrong target configuration. \$\endgroup\$ – Vicente Cunha May 8 '18 at 7:56
  • \$\begingroup\$ @Vincente I have used ARMCM4_FP simulated processor core. \$\endgroup\$ – Nirmal Anand May 8 '18 at 8:00

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service, privacy policy and cookie policy

Not the answer you're looking for? Browse other questions tagged or ask your own question.