Could you please help me with this question? Thank you in advance! 10. This prob

Question

Could you please help me with this question? Thank you in advance!

10. This problem is going to explore the limits of calculations in real-time environments. Suppose that we want to use our MSP430 board in an audio processing application. For example purposes only, assume that the CPU clock is 25Mhz, and the I/O clock is 44.1kHz. Our FIR filter is implemented with a linear buffer. Assume that a RAM access via the bus takes 10 CPU clock cycles, that a floating point MAC takes 250 CPU clock cycles, and that a fixed point MAC takes 70 CPU clock cycles (a) How many clock cycles do you have available to compute the output sample? Show your work. (b) What is the largest length FIR filter M that you can process using i. fixed point ii. floating point Show your reasoning.

Explanation / Answer

(a) According to MSP430, 240 samples @ 20kHz takes 12msec of time for execution.

Here in the problem it is given that 10 CPU clock cycles for RAM access, 250 CPU cycles for floating point MAC and 70 CPU cycles for fixed MAC.

The CPU clock frequency given is 25MHz. The CPU clock period is given by 1/25MHz i.e., 0.04micro seconds.

Number of clock cycles for 12msec is given by (12*10-3)/(0.04*10-6)=3,00,000 clock cycles for 240 samples.

For one sample 300000/240=1250

So, number clock cycles for one output sample is 1250 clock cycles.

(b) (i) given that fixed point MAC takes 70 CPU clock cycles. One clock cycle is of 0.04micro seconds. Therefore 70 CPU clock cycles takes 70*0.04micro seconds=2.8micro seconds.

Length of FIR is 2.8micro/0.04micro = 70

(ii) given floating point MAC takes 250 CPU cycles= 250*0.04micro=10micro

Length of FIR is 250

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