MSP430G2553: Integer conversion resuted in truncation

Joan Marc Riera Pera

Part Number: MSP430G2553

When trying to reset some bits in P1DIR register, i get this warning "Integer conversion resulted in truncation".

The line that gives problems is this one: P1DIR = ~(BIT1 | BIT7);

I have done it this way with other bits in this register, but i don't know why when i do it with bit7 it shows this warning. Isn't P1DIR an 8 bit register? anyone knows why is this warning popipg up?¿

It probably is a very dumb qüestion but i really cann't find what i am doing wrong here. Thank you very much in advance!

Joan Marc

over 5 years ago

+1 Keith Barkley over 5 years ago

Guru 43455 points

The ~ converts (BIT1|Bit7) into an integer, which you store in a Byte.

0 Joan Marc Riera Pera over 5 years ago in reply to Keith Barkley

Prodigy 170 points

Thank you very much for your answer! then i understand this "~" is causing this undesired integer conversion. However, which would be the correct way of reseting a couple of bits in a register? should i do this in two diferent lines of code? like P1DIR &= ~BIT1; and then in another line: P1DIR &= ~BIT7; ? i really thought this reseting of bits could be done in one line of code, because in some cases there is no problem in doing for example P1DIR &= ~(BIT2|BIT3);

+1 Keith Barkley over 5 years ago in reply to Joan Marc Riera Pera

Guru 43455 points

You could just cast it to a byte to shut off the warning.

0 Joan Marc Riera Pera over 5 years ago in reply to Keith Barkley

Prodigy 170 points

Thank you! I think it is not the first time you answer some of my questions. i have so much to learn.

If some wants to know, I did it like this: P1DIR = (char)~(BIT1|BIT7);

+1 Bruce McKenney over 5 years ago

Guru 102645 points

I think this (accidentally) highlighted something else you probably didn't intend to do. I suspect you wanted something like:

> P1DIR &= ~(BIT1 | BIT7); // Turn off (*only) bits 1 and 7

> P1DIR |= ZERO_CROSS; // Turn on (only) bit ZERO_CROSS

> P1REN &= ~(UCA0RXD | UCA0TXD); // Turn off resistors for TXD/RXD pins

0 Joan Marc Riera Pera over 5 years ago in reply to Bruce McKenney

Prodigy 170 points

Yes! well in this case i didn't put the &, because this is a config routine i only call at startup, and i wanted to set all bits except 1 and 7. But yes, i normally use the & to reset only the bits mentioned and leave the others alone.

Thank you for your comment!

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MSP430G2553: Integer conversion resuted in truncation