# SPI interface question

I was attempting this problem and I could not finish it.

I found the maximum frequency which was 67% as I divided 8 by 12(information bits/total bits), but I am having trouble finding the maximum utilization. The answer is 80%. I believe to find the utilization, you would divide the total packets per second over the total bits. To do that, I multiplied 300k with 0.67 and divided that number by 12. Can anyone explain to me where I went wrong?

Suppose a throughput of 10,000 16-bit samples is still required for the application, but the serial communication interface has the following characteristics:

• a total packet size of 12 bits: 8 bits of information and 4 bits of overhead

• does not require synchronization packets

• a bandwidth of 300,000 bits per second

What is the maximum efficiency and maximum utilization?

• Sounds like homework – Passerby Oct 27 '17 at 4:05
• quiz actually. No idea what went wrong. – AB408 Oct 27 '17 at 4:08
• The link efficiency is simply total information bits / total link bits. The utilisation is different. That is the number of bits per second required / bits per second available. – Peter Smith Oct 27 '17 at 14:40