Source code for hwtLib.examples.statements.fsm

#!/usr/bin/env python3
# -*- coding: utf-8 -*-

from hwt.code import FsmBuilder, Switch, If
from hwt.hdl.types.bits import Bits
from hwt.hdl.types.enum import HEnum
from hwt.interfaces.std import Signal, VectSignal
from hwt.interfaces.utils import addClkRstn
from hwt.synthesizer.unit import Unit


class FsmExample(Unit):
    """
    .. hwt-autodoc::
    """
    def _declr(self):
        addClkRstn(self)
        self.a = Signal()
        self.b = Signal()
        self.dout = VectSignal(3)._m()

    def _impl(self):
        # :note: stT member names are colliding with port names and thus
        #     they will be renamed in HDL
        stT = HEnum("st_t", ["a", "b", "aAndB"])

        a = self.a
        b = self.b
        out = self.dout

        st = FsmBuilder(self, stT)\
        .Trans(stT.a,
            (a & b, stT.aAndB),
            (b, stT.b)
        ).Trans(stT.b,
            (a & b, stT.aAndB),
            (a, stT.a)
        ).Trans(stT.aAndB,
            (a & ~b, stT.a),
            (~a & b, stT.b),
        ).stateReg

        Switch(st)\
        .Case(stT.a,
              out(1)
        ).Case(stT.b,
              out(2)
        ).Case(stT.aAndB,
              out(3)
        )


class HadrcodedFsmExample(FsmExample):
    """
    .. hwt-autodoc::
    """
    def _impl(self):
        a = self.a
        b = self.b
        out = self.dout

        st = self._reg("st", Bits(3), 1)

        If(st._eq(1),
            If(a & b,
                st(3)
            ).Elif(b,
                st(2)
            )
        ).Elif(st._eq(2),
            If(a & b,
               st(3)
            ).Elif(a,
                st(1)
            )
        ).Elif(st._eq(3),
            If(a & ~b,
               st(1)
            ).Elif(~a & b,
                st(2)
            )
        ).Else(
            st(1)
        )

        Switch(st)\
        .Case(1,
            out(1)
        ).Case(2,
            out(2)
        ).Case(3,
            out(3)
        ).Default(
            out(None)
        )


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