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70 lines
1.7 KiB
70 lines
1.7 KiB
library ieee;
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use ieee.std_logic_1164.all;
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use work.pkg.all;
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entity psl_fell is
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port (
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clk : in std_logic
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);
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end entity psl_fell;
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architecture psl of psl_fell is
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signal a, b, c : std_logic;
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begin
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-- 01234567890
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SEQ_A : sequencer generic map ("--__-_---__") port map (clk, a);
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SEQ_B : sequencer generic map ("_-__-_---__") port map (clk, b);
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SEQ_C : sequencer generic map ("__-__-___-_") port map (clk, c);
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-- All is sensitive to rising edge of clk
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default clock is rising_edge(clk);
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-- This assertion holds
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FELL_0_a : assert always (fell(a) -> c);
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-- This assertion holds
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FELL_1_a : assert always {a; not a} |-> fell(a);
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-- This assertion holds
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FELL_2_a : assert always (fell(a) -> (prev(a) and not a));
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-- Workaround needed before fell() is implemented
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-- With VHDL glue logic generating the
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-- previous value of a and simple comparing the two values
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d_reg : block is
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signal a_prev : std_logic := '0';
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begin
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process (clk) is
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begin
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if rising_edge(clk) then
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a_prev <= a;
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end if;
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end process;
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FELL_3_a : assert always (not a and a_prev -> c);
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end block d_reg;
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-- Another workaround by using simple SERE concatenation on LHS
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FELL_4_a : assert always {a; not a} |-> c;
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-- This assertion doesn't in formal tests
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-- in the 1st cycle. Problem is the value of
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-- a in the 0th cycle. So fell() can be safely
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-- used from the 2nd cycle on only
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FELL_5_a : assert always (fell(b) -> c);
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-- Stop simulation after longest running sequencer is finished
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-- Simulation only code by using pragmas
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-- synthesis translate_off
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stop_sim(clk, 11);
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-- synthesis translate_on
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end architecture psl;
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