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65C02: BE pin now operates as DBE (works in BBC Master)

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Change-Id: I85d3220158362bc304303f0a13280df38522f0a5
This commit is contained in:
David Banks 2020-01-29 14:47:20 +00:00
parent 11887e8f8c
commit 9bbefbe631
1 changed files with 20 additions and 4 deletions
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24
src/MOS6502CpuMonALS.vhd
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@ -104,6 +104,11 @@ architecture behavioral of MOS6502CpuMonALS is
signal led_trig0 : std_logic;
signal led_trig1 : std_logic;
signal PhiIn1 : std_logic;
signal PhiIn2 : std_logic;
signal PhiIn3 : std_logic;
signal PhiIn4 : std_logic;
begin
sw_reset_cpu <= not sw1;
@ -171,11 +176,22 @@ begin
ML_n <= '1';
VP_n <= '1';
process(clock)
begin
if rising_edge(clock) then
PhiIn1 <= PhiIn;
PhiIn2 <= PhiIn1;
PhiIn3 <= PhiIn2;
PhiIn4 <= PhiIn3;
end if;
end process;
-- Level Shifter Controls
OERW_n <= not (BE);
OEAH_n <= not (BE);
OEAL_n <= not (BE);
OED_n <= not (BE and PhiIn); -- TODO: might need to use a slightly delayed version of Phi2 here
OERW_n <= '0'; -- not (BE);
OEAH_n <= '0'; -- not (BE);
OEAL_n <= '0'; -- not (BE);
OED_n <= not (BE and PhiIn and PhiIn4); -- TODO: might need to use a slightly delayed version of Phi2 here
DIRD <= R_W_n_int;
end behavioral;