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path: root/src/main/scala/chisel3/util/random
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2019-05-09Add chisel3.util.random lib w/ LFSR generatorSchuyler Eldridge
Builds out PRNG and LFSR type hierarchy. PRNG is the base class of LFSR of which Galois and Fibonacci are concrete implementations. PRNGs contain state (a UInt) and an update (delta) function. They have a compile-time optional seed to set the PRNG state. The seed/state can also be set at run-time. PRNGs can be run-time parameterized based on how many updates they should do per cycle and whether or not to send the seed through step-count state updates before loading it. (h/t @jwright6323) LFSRs are parameterized in a reduction operation (XOR or XNOR). An LFSR that does NOT have a seed will be automatically initialized to a minimally safe state (set/reset one bit) based on their reduction operation. (h/t @aswaterman) Adds Galois and Fibonacci LFSRs that define appropriate update functions. Companion objects provide helpers to automatically generate maximal period variants. Taps are provide for a very large set of widths. The LFSR companion object provides an apply method to generate a Fibonacci LFSR random variable (like the old LFSR16).