verilog/rtl/ppcpu/rtl/core/pc.v

// SPDX-FileCopyrightText: 2022 Piotr Wegrzyn
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
//      http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.
// SPDX-License-Identifier: Apache-2.0

`include "config.v"
module pc #(parameter INT_VEC = `RW'b1) (
`ifdef USE_POWER_PINS
    inout vccd1,
    inout vssd1,
`endif

    input i_clk,
    input i_rst,

    output reg [`RW-1:0] o_pc,
    input [`RW-1:0] i_bus,

    input i_c_pc_inc,
    input i_c_pc_ie,
    input i_c_pc_irq,

    output o_pc_ovf
);

always @(posedge i_clk) begin
    if (i_rst) begin
        o_pc <= `RW'b0;
    end else if (i_c_pc_irq) begin
        o_pc <= INT_VEC;
    end else if (i_c_pc_ie) begin
        o_pc <= i_bus;
    end else if (i_c_pc_inc) begin
        o_pc <= o_pc + `RW'b1;
    end
end

assign o_pc_ovf = o_pc[14] & i_c_pc_inc & ~i_c_pc_irq & ~i_c_pc_ie; // due to address shifiting, pc overflows at 14th bit 

endmodule