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Add priority encoder and arbiter modules

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Alex Forencich 2018-10-29 17:55:47 -07:00
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/*
Copyright (c) 2014-2018 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

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/*
Copyright (c) 2014-2018 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
/*
* Priority encoder module
*/
module priority_encoder #
(
parameter WIDTH = 4,
// LSB priority: "LOW", "HIGH"
parameter LSB_PRIORITY = "LOW"
)
(
input wire [WIDTH-1:0] input_unencoded,
output wire output_valid,
output wire [$clog2(WIDTH)-1:0] output_encoded,
output wire [WIDTH-1:0] output_unencoded
);
// power-of-two width
parameter W1 = 2**$clog2(WIDTH);
parameter W2 = W1/2;
generate
if (WIDTH == 2) begin
// two inputs - just an OR gate
assign output_valid = |input_unencoded;
if (LSB_PRIORITY == "LOW") begin
assign output_encoded = input_unencoded[1];
end else begin
assign output_encoded = ~input_unencoded[0];
end
end else begin
// more than two inputs - split into two parts and recurse
// also pad input to correct power-of-two width
wire [$clog2(W2)-1:0] out1, out2;
wire valid1, valid2;
priority_encoder #(
.WIDTH(W2),
.LSB_PRIORITY(LSB_PRIORITY)
)
priority_encoder_inst1 (
.input_unencoded(input_unencoded[W2-1:0]),
.output_valid(valid1),
.output_encoded(out1)
);
priority_encoder #(
.WIDTH(W2),
.LSB_PRIORITY(LSB_PRIORITY)
)
priority_encoder_inst2 (
.input_unencoded({{W1-WIDTH{1'b0}}, input_unencoded[WIDTH-1:W2]}),
.output_valid(valid2),
.output_encoded(out2)
);
// multiplexer to select part
assign output_valid = valid1 | valid2;
if (LSB_PRIORITY == "LOW") begin
assign output_encoded = valid2 ? {1'b1, out2} : {1'b0, out1};
end else begin
assign output_encoded = valid1 ? {1'b0, out1} : {1'b1, out2};
end
end
endgenerate
// unencoded output
assign output_unencoded = 1 << output_encoded;
endmodule