I2C delay instruction cycle

Hiralal Mahato

Prodigy 70 points

Other Parts Discussed in Thread: MSP430F47193

I am using MSP430F47193. In that I2C code there is I2C delay function.

void I2C_Delay(void)
{
unsigned char Del=100; //50
while (Del--);
}

what is the time taken to complete these instructions.

over 8 years ago

0 zrno soli over 8 years ago

Guru 33653 points

At the beginning set output pin from low to high, and at the end set output pin back to low. Taken time can be measured by logic analyzer, or any other way you want.

0 Brian Boorman over 8 years ago in reply to zrno soli

Guru 25210 points

That is the empirical way to determine the time, but also assumes you have the equipment to measure it. Accuracy depends on where you place the GPIO pin setting/clearing instructions and the resolution of the measuring equipment.

Analytically, you would look at the generated machine code and count the instruction cycles per loop and multiply. To be totally accurate you would also add in the function call overhead. Total cycles divided by MCLK frequency (in Hz) gives you time delay in seconds. Accuracy only depends on the accuracy of the MCLK frequency.

0 zrno soli over 8 years ago in reply to Brian Boorman

Guru 33653 points

He can measure it by 5529 LP forum.43oh.com/.../3909-msp430f550x-based-logic-analyzer

0 Brian Boorman over 8 years ago in reply to zrno soli

Guru 25210 points

Again, that assumes that OP has that piece of equipment (a 5529 LP). And if they don't, then it can always be calculated analytically using the software they already have.

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I2C delay instruction cycle