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//
// Copyright 2012 Ettus Research LLC
//
//
// This module forms the qualification engine for a single master as
// part of a larger arbitration engine for a slave. It would typically
// be instantiated from arb_select_master.v to form a complete arbitor solution.
//
module arb_qualify_master
#(
parameter WIDTH=16 // Bit width of destination field.
)
(
input clk,
input reset,
input clear,
// Header signals
input [WIDTH-1:0] header,
input header_valid,
// Slave Confg Signals
input [WIDTH-1:0] slave_addr,
input [WIDTH-1:0] slave_mask,
input slave_valid,
// Arbitration flags
output reg master_valid,
input master_ack
);
localparam WAIT_HEADER_VALID = 0;
localparam MATCH = 1;
localparam WAIT_HEADER_NOT_VALID = 2;
reg [1:0] state, next_state;
// Does masked slave address match header field for dest from master?
assign header_match = ((header & slave_mask) == (slave_addr & slave_mask)) && slave_valid;
always @(posedge clk)
if (reset | clear) begin
state <= WAIT_HEADER_VALID;
master_valid <= 0;
end else
begin
case(state)
//
// Wait here until Masters FIFO presents a valid header word.
//
WAIT_HEADER_VALID: begin
if (header_valid)
if (header_match) begin
state <= MATCH;
master_valid <= 1;
end else
next_state <= WAIT_HEADER_NOT_VALID;
end
//
// There should only ever be one match across various arbitors
// if they are configured correctly and since the backing FIFO in the
// master should not start to drain until the arbitration is won
// by that master, master_ack should always preceed de-assertion of
// header_valid so we don't check for the other order of deassertion.
//
MATCH: begin
if (master_ack) begin
master_valid <= 0;
state <= WAIT_HEADER_NOT_VALID;
end
end
//
// Wait here until this master starts to drain this packet from his FIFO.
//
WAIT_HEADER_NOT_VALID: begin
if (!header_valid) begin
state <= WAIT_HEADER_VALID;
end
end
endcase // case(state)
end // else: !if(reset | clear)
endmodule // arb_qualify_master
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