from litesata.common import * from migen.actorlib.crc import CRCInserter, CRCChecker class CRCEngine(Module): """Cyclic Redundancy Check Engine Compute next CRC value from last CRC value and data input using an optimized asynchronous LFSR. Parameters ---------- width : int Width of the data bus and CRC. polynom : int Polynom of the CRC (ex: 0x04C11DB7 for IEEE 802.3 CRC) Attributes ---------- d : in Data input. last : in last CRC value. next : next CRC value. """ def __init__(self, width, polynom): self.d = Signal(width) self.last = Signal(width) self.next = Signal(width) ### def _optimize_eq(l): """ Replace even numbers of XORs in the equation with an equivalent XOR """ d = {} for e in l: if e in d: d[e] += 1 else: d[e] = 1 r = [] for key, value in d.items(): if value%2 != 0: r.append(key) return r new = Signal(32) self.comb += new.eq(self.last ^ self.d) # compute and optimize CRC's LFSR curval = [[("new", i)] for i in range(width)] for i in range(width): feedback = curval.pop() for j in range(width-1): if (polynom & (1<<(j+1))): curval[j] += feedback curval[j] = _optimize_eq(curval[j]) curval.insert(0, feedback) # implement logic for i in range(width): xors = [] for t, n in curval[i]: if t == "new": xors += [new[n]] self.comb += self.next[i].eq(optree("^", xors)) @DecorateModule(InsertReset) @DecorateModule(InsertCE) class LiteSATACRC(Module): """SATA CRC Implement a SATA CRC generator/checker Attributes ---------- value : out CRC value (used for generator). error : out CRC error (used for checker). """ width = 32 polynom = 0x04C11DB7 init = 0x52325032 check = 0x00000000 def __init__(self, dw=32): self.d = Signal(self.width) self.value = Signal(self.width) self.error = Signal() ### self.engine = CRCEngine(self.width, self.polynom) reg_i = Signal(self.width, reset=self.init) self.sync += reg_i.eq(self.engine.next) self.comb += [ self.engine.d.eq(self.d), self.engine.last.eq(reg_i), self.value.eq(reg_i), self.error.eq(self.engine.next != self.check) ] class LiteSATACRCInserter(CRCInserter): def __init__(self, description): CRCInserter.__init__(self, LiteSATACRC, description) class LiteSATACRCChecker(CRCChecker): def __init__(self, description): CRCChecker.__init__(self, LiteSATACRC, description)