MSP430F5244: Compiler conversion of intrinsic functions

Conor

Part Number: MSP430F5244

Hi, MSP430 Support team

I will ask you a question from "Related Questions".

Last time, Mr. Dennis gave me the opinion that if you want to write a value to SR, you need to write it with the BIS instruction.

I have a questions about that.

The table below is a screenshot from the compiler guide.

The above is stated that if I use __bis_SR_register() of intrinsic function, the compiler will be converted to BIS.

However, I checked it also converted BISX.

Is this a compiler bug?

If it is not a compiler bug, please tell me the conversion rules for BIS and BISX of the compiler.

The following is the source code and screenshot that is converted to BISX instructions.

Fullscreen 1325.main.c Download

#include <msp430.h>

#define set_LPM_Mode(x) __bis_SR_register(x)
static const unsigned short SET_LP_MODE[5]={GIE, LPM0_bits|GIE, LPM1_bits|GIE, LPM2_bits|GIE, LPM3_bits|GIE};
unsigned int count=4;

int main(void)
{

    WDTCTL = WDTPW + WDTHOLD; // Stop watchdog timer

    while(1)
    {
        set_LPM_Mode(SET_LP_MODE[count]); // Enter LPM3
        __no_operation();                 // For debugger
    }
}

Best Regards,

Koki

over 5 years ago

0 Lixin Chen1 over 5 years ago

TI__Expert 7015 points

Hi, Koki,

The BISX.w is to set bits set in source word in destination word.

In your example, I don't know how the set_LPM_Mode(SET_LP_MODE[count]) works. Could you try to replace it with _BIS_SR(LPM3_bits + GIE); to see any difference?

Thanks,

Lixin

0 Conor over 5 years ago in reply to Lixin Chen1

Guru 14700 points

Hi, Lixin

Lixin Chen1 said:
_BIS_SR(LPM3_bits + GIE)

With the above writing method, it was confirmed that BIS.W is written to SR.

Is it a compiler bug that was converted to BISX when writing to SR by my customer's description method?

Thanks,

Koki

0 David Schultz over 5 years ago in reply to Conor

Guru 26085 points

The use of BISX is triggered by the indexed addressing mode for the source.

0 Conor over 5 years ago in reply to David Schultz

Guru 14700 points

Hi,

David Schultz said:
The use of BISX is triggered by the indexed addressing mode for the source.

In this case, it is caused by calling the LPM setting bits with an array, isn't it?

Also, does the documentation state that indexed address mode is a factor in converting to BISX?

Thanks,

Koki

0 David Schultz over 5 years ago in reply to Conor

Guru 26085 points

BISX uses 20 address bits (BIS uses 16) and you clearly have compiled with settings telling the compiler to use 20 bit addresses.

The compiler doesn't know the range of your index variable so must assume the worst.

0 Conor over 5 years ago in reply to David Schultz

Guru 14700 points

Hi,

David Schultz said:
you clearly have compiled with settings telling the compiler to use 20 bit addresses.

The compiler doesn't know the range of your index variable so must assume the worst.

I'm sorry, but I don't really understand what you are saying. What kind of C description do you mean?

Could you tell me a little more detail?

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MSP430F5244: Compiler conversion of intrinsic functions