| /* |
| |
| Copyright (c) 2014-2016 Alex Forencich |
| |
| Permission is hereby granted, free of charge, to any person obtaining a copy |
| of this software and associated documentation files (the "Software"), to deal |
| in the Software without restriction, including without limitation the rights |
| to use, copy, modify, merge, publish, distribute, sublicense, and/or sell |
| copies of the Software, and to permit persons to whom the Software is |
| furnished to do so, subject to the following conditions: |
| |
| The above copyright notice and this permission notice shall be included in |
| all copies or substantial portions of the Software. |
| |
| THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR |
| IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY |
| FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE |
| AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER |
| LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, |
| OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN |
| THE SOFTWARE. |
| |
| */ |
| |
| // Language: Verilog 2001 |
| |
| `timescale 1ns / 1ps |
| |
| /* |
| * Arbiter module |
| */ |
| module arbiter # |
| ( |
| parameter PORTS = 4, |
| // arbitration type: "PRIORITY" or "ROUND_ROBIN" |
| parameter TYPE = "PRIORITY", |
| // block type: "NONE", "REQUEST", "ACKNOWLEDGE" |
| parameter BLOCK = "NONE", |
| // LSB priority: "LOW", "HIGH" |
| parameter LSB_PRIORITY = "LOW" |
| ) |
| ( |
| input wire clk, |
| input wire rst, |
| |
| input wire [PORTS-1:0] request, |
| input wire [PORTS-1:0] acknowledge, |
| |
| output wire [PORTS-1:0] grant, |
| output wire grant_valid, |
| output wire [$clog2(PORTS)-1:0] grant_encoded |
| ); |
| |
| reg [PORTS-1:0] grant_reg = 0, grant_next; |
| reg grant_valid_reg = 0, grant_valid_next; |
| reg [$clog2(PORTS)-1:0] grant_encoded_reg = 0, grant_encoded_next; |
| |
| assign grant_valid = grant_valid_reg; |
| assign grant = grant_reg; |
| assign grant_encoded = grant_encoded_reg; |
| |
| wire request_valid; |
| wire [$clog2(PORTS)-1:0] request_index; |
| wire [PORTS-1:0] request_mask; |
| |
| priority_encoder #( |
| .WIDTH(PORTS), |
| .LSB_PRIORITY(LSB_PRIORITY) |
| ) |
| priority_encoder_inst ( |
| .input_unencoded(request), |
| .output_valid(request_valid), |
| .output_encoded(request_index), |
| .output_unencoded(request_mask) |
| ); |
| |
| reg [PORTS-1:0] mask_reg = 0, mask_next; |
| |
| wire masked_request_valid; |
| wire [$clog2(PORTS)-1:0] masked_request_index; |
| wire [PORTS-1:0] masked_request_mask; |
| |
| priority_encoder #( |
| .WIDTH(PORTS), |
| .LSB_PRIORITY(LSB_PRIORITY) |
| ) |
| priority_encoder_masked ( |
| .input_unencoded(request & mask_reg), |
| .output_valid(masked_request_valid), |
| .output_encoded(masked_request_index), |
| .output_unencoded(masked_request_mask) |
| ); |
| |
| always @* begin |
| grant_next = 0; |
| grant_valid_next = 0; |
| grant_encoded_next = 0; |
| mask_next = mask_reg; |
| |
| if (BLOCK == "REQUEST" && grant_reg & request) begin |
| // granted request still asserted; hold it |
| grant_valid_next = grant_valid_reg; |
| grant_next = grant_reg; |
| grant_encoded_next = grant_encoded_reg; |
| end else if (BLOCK == "ACKNOWLEDGE" && grant_valid && !(grant_reg & acknowledge)) begin |
| // granted request not yet acknowledged; hold it |
| grant_valid_next = grant_valid_reg; |
| grant_next = grant_reg; |
| grant_encoded_next = grant_encoded_reg; |
| end else if (request_valid) begin |
| if (TYPE == "PRIORITY") begin |
| grant_valid_next = 1; |
| grant_next = request_mask; |
| grant_encoded_next = request_index; |
| end else if (TYPE == "ROUND_ROBIN") begin |
| if (masked_request_valid) begin |
| grant_valid_next = 1; |
| grant_next = masked_request_mask; |
| grant_encoded_next = masked_request_index; |
| if (LSB_PRIORITY == "LOW") begin |
| mask_next = {PORTS{1'b1}} >> (PORTS - masked_request_index); |
| end else begin |
| mask_next = {PORTS{1'b1}} << (masked_request_index + 1); |
| end |
| end else begin |
| grant_valid_next = 1; |
| grant_next = request_mask; |
| grant_encoded_next = request_index; |
| if (LSB_PRIORITY == "LOW") begin |
| mask_next = {PORTS{1'b1}} >> (PORTS - request_index); |
| end else begin |
| mask_next = {PORTS{1'b1}} << (request_index + 1); |
| end |
| end |
| end |
| end |
| end |
| |
| always @(posedge clk) begin |
| if (rst) begin |
| grant_reg <= 0; |
| grant_valid_reg <= 0; |
| grant_encoded_reg <= 0; |
| mask_reg <= 0; |
| end else begin |
| grant_reg <= grant_next; |
| grant_valid_reg <= grant_valid_next; |
| grant_encoded_reg <= grant_encoded_next; |
| mask_reg <= mask_next; |
| end |
| end |
| |
| endmodule |