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Z80: Fix timing of monitor IO cycles

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Change-Id: I8c6251afc2e2aaeaa6612458d872e448d6386ea8
This commit is contained in:
David Banks 2019-11-08 09:53:47 +00:00
parent 41c7216c30
commit 38c57c75a3
1 changed files with 13 additions and 7 deletions
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20
src/Z80CpuMon.vhd
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@ -137,7 +137,8 @@ type state_type is (idle, nop_t1, nop_t2, nop_t3, nop_t4, rd_t1, rd_wa, rd_t2, r
signal memory_rd1 : std_logic;
signal memory_wr1 : std_logic;
signal mon_m1_n : std_logic;
signal mon_xx_n : std_logic;
signal mon_xx_n : std_logic; -- shorten MREQ and RD in M1 NOP cycle
signal mon_yy : std_logic; -- delay IORQ/RD/WR in IO cycle
signal mon_mreq_n : std_logic;
signal mon_iorq_n : std_logic;
signal mon_rfsh_n : std_logic;
@ -399,9 +400,9 @@ begin
-- The mon_ versions come from the state machine below
MREQ_n <= MREQ_n_int when state = idle else mon_mreq_n and mon_xx_n;
IORQ_n <= IORQ_n_int when state = idle else mon_iorq_n;
WR_n <= WR_n_int when state = idle else mon_wr_n;
RD_n <= RD_n_int when state = idle else mon_rd_n and mon_xx_n;
IORQ_n <= IORQ_n_int when state = idle else (mon_iorq_n or mon_yy);
WR_n <= WR_n_int when state = idle else (mon_wr_n or mon_yy);
RD_n <= RD_n_int when state = idle else (mon_rd_n or mon_yy) and mon_xx_n;
RFSH_n <= RFSH_n_int when state = idle else mon_rfsh_n;
M1_n <= M1_n_int when state = idle else mon_m1_n;
@ -433,11 +434,11 @@ begin
end if;
end process;
Data <= memory_dout when state = wr_wa or state = wr_t2 or state = wr_t3 else
Data <= memory_dout when (state = wr_t1 and io_not_mem = '1') or state = wr_wa or state = wr_t2 or state = wr_t3 else
Dout when state = idle and Den = '1' else
(others => 'Z');
DIRD <= '0' when state = wr_wa or state = wr_t2 or state = wr_t3 else
DIRD <= '0' when (state = wr_t1 and io_not_mem = '1') or state = wr_wa or state = wr_t2 or state = wr_t3 else
'0' when state = idle and Den = '1' else
'1';
@ -455,6 +456,7 @@ begin
mon_rfsh_n <= '1';
mon_m1_n <= '1';
mon_xx_n <= '1';
mon_yy <= '0';
mon_busak_n1 <= '1';
elsif rising_edge(CLK_n) then
@ -531,9 +533,11 @@ begin
elsif memory_wr1 = '1' or io_wr1 = '1' then
state <= wr_t1;
io_not_mem <= io_wr1;
mon_yy <= io_wr1;
elsif memory_rd1 = '1' or io_rd1 = '1' then
state <= rd_t1;
io_not_mem <= io_rd1;
mon_yy <= io_rd1;
else
state <= nop_t1;
mon_m1_n <= mode;
@ -541,6 +545,7 @@ begin
-- Read cycle
when rd_t1 =>
mon_yy <= '0';
if io_not_mem = '1' then
state <= rd_wa;
else
@ -565,6 +570,7 @@ begin
-- Write cycle
when wr_t1 =>
mon_yy <= '0';
if io_not_mem = '1' then
state <= wr_wa;
else
@ -631,7 +637,7 @@ begin
mon_rd_n <= '1';
end if;
-- Write strobe
if state = wr_wa or state = wr_t2 then
if (state = wr_t1 and io_not_mem = '1') or state = wr_wa or state = wr_t2 then
mon_wr_n <= '0';
else
mon_wr_n <= '1';