Can somebody please explain "While (!(UCB0IFG & UCTXIFG))" statement in detail?

Jayesh Parmar

Prodigy 215 points

Other Parts Discussed in Thread: MSP430F5438A

While (!(UCB0IFG & UCTXIFG));

UCB0TXBUF=0X01;

Plz explain in detail. It is used for spi communication between msp430f5438a and an transceiver ic.

over 9 years ago

0 Ryan Brown1 over 9 years ago

TI__Guru**** 218477 points

Loop until the UCTXIFG bit inside of the UCB0IFG register is set, indicating that the UCBxTXBUF is ready for new data and an interrupt is pending. The UCTXIFG bit is automatically cleared once a character is written to UCBxTXBUF.

Regards,
Ryan

0 Jayesh Parmar over 9 years ago in reply to Ryan Brown1

Prodigy 215 points

UCB0IFG is a register and UCTXIFG is a single flag bit. How these two can be ANDed.? and the output should be a single bit (1 or 0) for the " While" to function.

0 Ryan Brown1 over 9 years ago in reply to Jayesh Parmar

TI__Guru**** 218477 points

UCTXIFG = 0x02 which is ANDed with the value stored in the UCB0IFG register's location, this operation compares the register against the specific bit and either returns a 0 or not 0 (effectively a 1) for the while loop to interpret. This kind of while loop flag check is quite common for MSP430 C coding.

Regards,
Ryan

0 Jayesh Parmar over 9 years ago in reply to Ryan Brown1

Prodigy 215 points

Can't we write "While (!UCTXIFG)" instead?

0 Ryan Brown1 over 9 years ago in reply to Jayesh Parmar

TI__Guru**** 218477 points

No because UCTXIFG is a set value (0x02), it doesn't refer to the actual register in any way.

Regards,
Ryan

0 Jayesh Parmar over 9 years ago in reply to Ryan Brown1

Prodigy 215 points

Got it. Thanks for the explanation.

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Can somebody please explain "While (!(UCB0IFG & UCTXIFG))" statement in detail?