Source code for hwtLib.logic.crcComb

from hwt.bitmask import selectBit
from hwt.interfaces.std import VectSignal
from hwt.interfaces.utils import addClkRstn
from hwt.synthesizer.unit import Unit
from hwt.synthesizer.param import Param
from hwt.synthesizer.vectorUtils import iterBits
from hwtLib.logic.crcPoly import CRC_5_USB
from hwtLib.logic.crcUtils import parsePolyStr, buildCrcMatrix_dataMatrix


# http://www.sunshine2k.de/coding/javascript/crc/crc_js.html
[docs]class CrcComb(Unit):
    """
    CRC generator
    polynomial can be string in usual format or integer (f.e."x^3+x+1" or 0b1011)

    @attention: Input not reflected, Result not reflected, Initial Value: 0x0, Final Xor Value: 0x0
    """
[docs]    def _config(self):
        self.DATA_WIDTH = Param(5)

        self.POLY = Param(CRC_5_USB)
        self.POLY_WIDTH = Param(5)

[docs]    def _declr(self):
        addClkRstn(self)
        with self._paramsShared():
            self.dataIn = VectSignal(self.DATA_WIDTH)
            self.dataOut = VectSignal(self.POLY_WIDTH)

[docs]    def parsePoly(self):
        PW = int(self.POLY_WIDTH)
        poly = int(self.POLY)
        if isinstance(poly, str):
            polyCoefs = parsePolyStr(poly, PW)
        elif isinstance(poly, int):
            polyCoefs = [selectBit(poly, i) for i in range(PW)]
        else:
            raise NotImplementedError()

        return polyCoefs, PW

[docs]    def _impl(self):
        DW = int(self.DATA_WIDTH)
        # assert PW == DW
        polyCoefs, PW = self.parsePoly()
        xorMatrix = buildCrcMatrix_dataMatrix(polyCoefs, PW, DW)

        for outBit, inMask in zip(iterBits(self.dataOut),
                                  xorMatrix):
            bit = None
            for m, b in zip(reversed(inMask), iterBits(self.dataIn)):
                if m:
                    if bit is None:
                        bit = b
                    else:
                        bit = bit ^ b
            assert bit is not None

            outBit(bit)


if __name__ == "__main__":
    from hwt.synthesizer.utils import toRtl
    u = CrcComb()
    print(toRtl(u))