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Add LSB_PRIORITY parameter

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This commit is contained in:
Alex Forencich 2014-11-16 01:58:17 -08:00
parent b123525597
commit d193ca5905
2 changed files with 34 additions and 10 deletions
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22
rtl/arbiter.v
View File

@ -35,7 +35,9 @@ module arbiter #
// arbitration type: "PRIORITY" or "ROUND_ROBIN"
parameter TYPE = "PRIORITY",
// block type: "NONE", "REQUEST", "ACKNOWLEDGE"
parameter BLOCK = "NONE"
parameter BLOCK = "NONE",
// LSB priority: "LOW", "HIGH"
parameter LSB_PRIORITY = "LOW"
)
(
input wire clk,
@ -62,7 +64,8 @@ wire [$clog2(PORTS)-1:0] request_index;
wire [PORTS-1:0] request_mask;
priority_encoder #(
.WIDTH(PORTS)
.WIDTH(PORTS),
.LSB_PRIORITY(LSB_PRIORITY)
)
priority_encoder_inst (
.input_unencoded(request),
@ -78,7 +81,8 @@ wire [$clog2(PORTS)-1:0] masked_request_index;
wire [PORTS-1:0] masked_request_mask;
priority_encoder #(
.WIDTH(PORTS)
.WIDTH(PORTS),
.LSB_PRIORITY(LSB_PRIORITY)
)
priority_encoder_masked (
.input_unencoded(request & mask_reg),
@ -113,12 +117,20 @@ always @* begin
grant_valid_next = 1;
grant_next = masked_request_mask;
grant_encoded_next = masked_request_index;
mask_next = {PORTS{1'b1}} >> (PORTS - 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;
mask_next = {PORTS{1'b1}} >> (PORTS - 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

22
rtl/priority_encoder.v
View File

@ -31,7 +31,9 @@ THE SOFTWARE.
*/
module priority_encoder #
(
parameter WIDTH = 4
parameter WIDTH = 4,
// LSB priority: "LOW", "HIGH"
parameter LSB_PRIORITY = "LOW"
)
(
input wire [WIDTH-1:0] input_unencoded,
@ -48,14 +50,19 @@ generate
if (WIDTH == 2) begin
// two inputs - just an OR gate
assign output_valid = |input_unencoded;
assign output_encoded = input_unencoded[1];
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)
.WIDTH(W2),
.LSB_PRIORITY(LSB_PRIORITY)
)
priority_encoder_inst1 (
.input_unencoded(input_unencoded[W2-1:0]),
@ -63,7 +70,8 @@ generate
.output_encoded(out1)
);
priority_encoder #(
.WIDTH(W2)
.WIDTH(W2),
.LSB_PRIORITY(LSB_PRIORITY)
)
priority_encoder_inst2 (
.input_unencoded({{W1-WIDTH{1'b0}}, input_unencoded[WIDTH-1:W2]}),
@ -72,7 +80,11 @@ generate
);
// multiplexer to select part
assign output_valid = valid1 | valid2;
assign output_encoded = valid2 ? {1'b1, out2} : {1'b0, out1};
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