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POFinding the next in round-robin scheduling by bit twiddling
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copied!<p>Consider the following problem. You have a bit-string that represents the current scheduled slave in one-hot encoding. For example, "00000100" (with the leftmost bit being #7 and rightmost #0) means that slave #2 is scheduled. </p> <p>Now, I want to pick the next scheduled slave in a round-robin scheduling scheme, with a twist. I have a "request mask" which says which slaves actually want to be scheduled. The next slave will be picked only from those that want to.</p> <p>Some examples (assume round-robin scheduling is done by rotating left). Example1:</p> <ul> <li>Current: "00000100"</li> <li>Mask: "01100000"</li> <li>Next schedule: "00100000" - in normal round-robin, #3 and then #4 should come after #2, but they don't request, so #5 is picked.</li> </ul> <p>Example2:</p> <ul> <li>Current: "01000000"</li> <li>Mask: "00001010"</li> <li>Next: "00000010" - because scheduling is done by cycling left, and #1 is the first requesting slave in that order.</li> </ul> <hr> <p>Now, this can be easily coded in a loop, I know. But I actually want to get my result by a bit-twiddling operation, without loops. The motivation: I want to implement this in hardware (in an FPGA) in VHDL/Verilog.</p> <p>A bonus is to make up an algorithm that's generic for any amount of slaves N.</p> <p>By the way, this is not a homework question. It's an important problem whenever one wants to schedule slaves in some manner, and condition the scheduling by the slaves' requests. My current solution is somewhat "heavy" and I wanted to know if I'm missing something obvious.</p>

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