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Z80: Sample IM2 vector at start of T3, not middle 

Change-Id: I902d5993e35da092b8b702fc21b3fbcbef4cc8c3
This commit is contained in:
David Banks 2021-03-21 17:43:51 +00:00
parent 6abb27cfbe
commit dc2db74cc3
1 changed files with 9 additions and 2 deletions
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11
src/T80/T80.vhd
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@ -380,6 +380,7 @@ architecture rtl of T80 is
signal Halt : std_logic;
signal XYbit_undoc : std_logic;
signal DOR : std_logic_vector(127 downto 0);
signal IVector : std_logic_vector(7 downto 0);
begin
@ -578,6 +579,12 @@ begin
IR <= "11111111";
elsif Halt_FF = '1' or (IntCycle = '1' and IStatus = "10") or NMICycle = '1' then
IR <= "00000000";
-- DMB: It's important to catch the interrupt vector at
-- the start of T3, not the middle as the old code
-- (using WZ) did. This caused a issue with the Z80
-- Second Processor on the GODIL due to the pullups
-- (esp on D0)
IVector <= DInst;
else
IR <= DInst;
end if;
@ -631,9 +638,9 @@ begin
PC <= "0000000001100110";
elsif MCycle = "011" and IntCycle = '1' and IStatus = "10" then
A(15 downto 8) <= I;
A(7 downto 0) <= WZ(7 downto 0);
A(7 downto 0) <= IVector;
PC(15 downto 8) <= unsigned(I);
PC(7 downto 0) <= unsigned(WZ(7 downto 0));
PC(7 downto 0) <= unsigned(IVector);
else
case Set_Addr_To is
when aXY =>