Subversion Repositories myblaze

# -*- coding: utf-8 -*-

"""

    fetch.py

    ========

    Fetch Unit

    :copyright: Copyright (c) 2010 Jian Luo.

    :author-email: jian <dot> luo <dot> cn <at> gmail <dot> com.

    :license: BSD, see LICENSE for details.

    :revision: $Id: fetch.py 3 2010-11-21 07:17:00Z rockee $

"""

from myhdl import *

from defines import *

from functions import *

def FetchUnit(

        clock,

        reset,

        enable,

        of_hazard,

        ex_alu_result,

        ex_branch,

        if_program_counter,

        imem_addr_out,

        imem_ena_out,

        ):

    """

    """

    MAX_IMEM_ADDR = 2**CFG_IMEM_SIZE

    if_comb_r_program_counter = Signal(intbv(0)[CFG_IMEM_SIZE:])

    if_r_program_counter = Signal(intbv(0)[CFG_IMEM_SIZE:])

    @always_comb

    def comb():

        program_counter = intbv(0)[CFG_IMEM_SIZE:]

        if reset:

            program_counter[:] = 0

        elif of_hazard:

            program_counter[:] = if_r_program_counter

        elif ex_branch:

            program_counter[:] = ex_alu_result[CFG_IMEM_SIZE:]

        else:

            #program_counter[:] = ((if_r_program_counter[CFG_IMEM_SIZE:2]+1)

                                    #<< 2) % MAX_IMEM_ADDR

            program_counter[:] = (if_r_program_counter+4) % MAX_IMEM_ADDR

        if_comb_r_program_counter.next = program_counter

        #if ex_branch:

            #program_counter[:] = ex_alu_result[CFG_IMEM_SIZE:]

        #else:

            #program_counter[:] = if_r_program_counter

            ###program_counter[:] = ((if_r_program_counter[CFG_IMEM_SIZE:2]+1)

                                    ###<< 2) % MAX_IMEM_ADDR

            ##program_counter[:] = (if_r_program_counter+4) % MAX_IMEM_ADDR

        #if_program_counter.next = program_counter

        #imem_addr_out.next = program_counter

        #if of_hazard:

            #if_comb_r_program_counter.next = program_counter

        #else:

            #if_comb_r_program_counter.next = (program_counter+4) % MAX_IMEM_ADDR

    @always(clock.posedge)

    def seq():

        if reset:

            if_r_program_counter.next = 0

        elif enable:

            if_r_program_counter.next = if_comb_r_program_counter

        #if __debug__:

            #print 'pc:=0x%x, enable:=%s, reset:=%s' % (

                #if_comb_r_program_counter, enable, reset)

    @always_comb

    def regout():

        imem_ena_out.next = enable

        imem_addr_out.next = if_comb_r_program_counter

        #if __debug__:

            #imem_addr_out.next = if_r_program_counter

        if_program_counter.next = if_r_program_counter

    return instances()

if __name__ == '__main__':

    clock = Signal(False)

    reset = Signal(False)

    enable = Signal(False)

    imem_addr_out = Signal(intbv(0)[CFG_IMEM_SIZE:])

    imem_ena_out = Signal(False)

    if_program_counter = Signal(intbv(0)[CFG_IMEM_SIZE:])

    of_hazard = Signal(False)

    ex_alu_result = Signal(intbv(0)[32:])

    ex_branch = Signal(False)

    args = [

        FetchUnit,

        clock,

        reset,

        enable,

        of_hazard,

        ex_alu_result,

        ex_branch,

        if_program_counter,

        imem_addr_out,

        imem_ena_out,

    ]

    toVHDL(*args)

    toVerilog(*args)

### EOF ###

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