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93 lines
2.5 KiB
93 lines
2.5 KiB
-- simple queue protected type
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-- inspired by noasic article http://noasic.com/blog/a-simple-fifo-using-vhdl-protected-types/
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library ieee;
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use ieee.std_logic_1164.all;
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package QueueP is
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type t_simple_queue is protected
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procedure push (data : in std_logic_vector);
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procedure pop (data : out std_logic_vector);
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impure function is_empty return boolean;
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impure function is_full return boolean;
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impure function fillstate return natural;
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impure function freeslots return natural;
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end protected t_simple_queue;
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end package QueueP;
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package body QueueP is
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type t_simple_queue is protected body
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constant C_QUEUE_DEPTH : natural := 64;
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constant C_QUEUE_WIDTH : natural := 64;
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type t_queue_array is array (0 to C_QUEUE_DEPTH-1) of std_logic_vector(C_QUEUE_WIDTH-1 downto 0);
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variable v_queue : t_queue_array := (others => (others => '0'));
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variable v_count : natural range 0 to t_queue_array'length := 0;
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variable v_head : natural range 0 to t_queue_array'high := 0;
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variable v_tail : natural range 0 to t_queue_array'high := 0;
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-- write one entry into queue
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procedure push (data : in std_logic_vector) is
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begin
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assert not(is_full)
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report "push into full queue -> discarded"
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severity failure;
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v_queue(v_head) := data;
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v_head := (v_head + 1) mod t_queue_array'length;
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v_count := v_count + 1;
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end procedure push;
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-- read one entry from queue
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procedure pop (data : out std_logic_vector) is
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begin
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assert not(is_empty)
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report "pop from empty queue -> discarded"
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severity failure;
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data := v_queue(v_tail);
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v_tail := (v_tail + 1) mod t_queue_array'length;
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v_count := v_count - 1;
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end procedure pop;
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-- returns true if queue is empty, false otherwise
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impure function is_empty return boolean is
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begin
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return v_count = 0;
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end function is_empty;
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-- returns true if queue is full, false otherwise
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impure function is_full return boolean is
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begin
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return v_count = t_queue_array'length;
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end function is_full;
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-- returns number of filled slots in queue
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impure function fillstate return natural is
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begin
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return v_count;
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end function fillstate;
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-- returns number of free slots in queue
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impure function freeslots return natural is
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begin
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return t_queue_array'length - v_count;
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end function freeslots;
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end protected body t_simple_queue;
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end package body QueueP;
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