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T80a: port from Z80n

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Gyorgy Szombathelyi
2021-03-31 00:41:13 +02:00
parent 0917cdf114
commit 830fd0315f
1 changed files with 156 additions and 107 deletions
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263
T80a.vhd
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@@ -67,11 +67,12 @@
--
-- 0247 : Fixed bus req/ack cycle
--
-- 0247a: 7th of September, 2003 by Kazuhiro Tsujikawa (tujikawa@hat.hi-ho.ne.jp)
-- Fixed IORQ_n, RD_n, WR_n bus timing
--
-- 0250 : Added R800 Multiplier by TobiFlex 2017.10.15
--
-- Bus signal logic changes from the ZX Spectrum Next were made by:
--
-- Fabio Belavenuto, Charlie Ingley
--
library IEEE;
use IEEE.std_logic_1164.all;
@@ -113,15 +114,20 @@ architecture rtl of T80a is
signal NoRead : std_logic;
signal Write : std_logic;
signal MREQ : std_logic;
signal MReq_Inhibit : std_logic;
signal IReq_Inhibit : std_logic; -- 0247a
signal Req_Inhibit : std_logic;
signal RD : std_logic;
signal MREQ_n_i : std_logic;
signal IORQ_n_i : std_logic;
signal RD_n_i : std_logic;
signal WR_n_i : std_logic;
signal WR_n_j : std_logic; -- 0247a
signal MReq_Inhibit : std_logic;
signal Req_Inhibit : std_logic;
signal RD : std_logic;
signal MREQ_n_i : std_logic;
signal MREQ_rw : std_logic; -- 30/10/19 Charlie Ingley-- add MREQ control
signal IORQ_n_i : std_logic;
signal IORQ_t1 : std_logic; -- 30/10/19 Charlie Ingley-- add IORQ control
signal IORQ_t2 : std_logic; -- 30/10/19 Charlie Ingley-- add IORQ control
signal IORQ_rw : std_logic; -- 30/10/19 Charlie Ingley-- add IORQ control
signal IORQ_int : std_logic; -- 30/10/19 Charlie Ingley-- add IORQ interrupt control
signal IORQ_int_inhibit : std_logic_vector(2 downto 0);
signal RD_n_i : std_logic;
signal WR_n_i : std_logic;
signal WR_t2 : std_logic; -- 30/10/19 Charlie Ingley-- add WR control
signal RFSH_n_i : std_logic;
signal BUSAK_n_i : std_logic;
signal A_i : std_logic_vector(15 downto 0);
@@ -135,15 +141,18 @@ begin
CEN <= '1';
BUSAK_n <= BUSAK_n_i;
MREQ_n_i <= not MREQ or (Req_Inhibit and MReq_Inhibit);
RD_n_i <= not RD or Req_Inhibit;
WR_n_j <= WR_n_i; -- 0247a
BUSAK_n <= BUSAK_n_i; -- 30/10/19 Charlie Ingley - IORQ/RD/WR changes
MREQ_rw <= MREQ and (Req_Inhibit or MReq_Inhibit); -- added MREQ timing control
MREQ_n_i <= not MREQ_rw; -- changed MREQ generation
IORQ_rw <= IORQ and not (IORQ_t1 or IORQ_t2); -- added IORQ generation timing control
IORQ_n_i <= not ((IORQ_int and not IORQ_int_inhibit(2)) or IORQ_rw); -- changed IORQ generation
RD_n_i <= not (RD and (MREQ_rw or IORQ_rw)); -- changed RD/IORQ generation
WR_n_i <= not (Write and ((WR_t2 and MREQ_rw) or IORQ_rw)); -- added WR/IORQ timing control
MREQ_n <= MREQ_n_i when BUSAK_n_i = '1' else 'Z';
IORQ_n <= IORQ_n_i or IReq_Inhibit when BUSAK_n_i = '1' else 'Z'; -- 0247a
IORQ_n <= IORQ_n_i when BUSAK_n_i = '1' else 'Z';
RD_n <= RD_n_i when BUSAK_n_i = '1' else 'Z';
WR_n <= WR_n_j when BUSAK_n_i = '1' else 'Z'; -- 0247a
WR_n <= WR_n_i when BUSAK_n_i = '1' else 'Z';
RFSH_n <= RFSH_n_i when BUSAK_n_i = '1' else 'Z';
A <= A_i when BUSAK_n_i = '1' else (others => 'Z');
D <= DO when Write = '1' and BUSAK_n_i = '1' else (others => 'Z');
@@ -195,99 +204,139 @@ begin
end if;
end process;
process (CLK_n) -- 0247a
begin
if CLK_n'event and CLK_n = '1' then
IReq_Inhibit <= not IORQ;
end if;
end process;
-- 30/10/19 Charlie Ingley - Generate WR_t2 to correct MREQ/WR timing
process (Reset_s,CLK_n)
begin
if Reset_s = '0' then
WR_t2 <= '0';
elsif CLK_n'event and CLK_n = '0' then
if MCycle /= "001" then
if TState = "010" then -- WR starts on falling edge of T2 for MREQ
WR_t2 <= Write;
end if;
end if;
if TState = "011" then -- end WR
WR_t2 <= '0';
end if;
end if;
end process;
process (Reset_s,CLK_n) -- 0247a
begin
if Reset_s = '0' then
WR_n_i <= '1';
elsif CLK_n'event and CLK_n = '0' then
if (IORQ = '0') then
if TState = "010" then
WR_n_i <= not Write;
elsif Tstate = "011" then
WR_n_i <= '1';
end if;
else
if TState = "001" and IORQ_n_i = '0' then
WR_n_i <= not Write;
elsif Tstate = "011" then
WR_n_i <= '1';
end if;
end if;
end if;
end process;
-- Generate Req_Inhibit
process (Reset_s,CLK_n)
begin
if Reset_s = '0' then
Req_Inhibit <= '1'; -- Charlie Ingley 30/10/19 - changed Req_Inhibit polarity
elsif CLK_n'event and CLK_n = '1' then
if MCycle = "001" and TState = "010" and WAIT_n = '1' then -- by Fabio Belavenuto - fix behavior of Wait_n
Req_Inhibit <= '0';
else
Req_Inhibit <= '1';
end if;
end if;
end process;
process (Reset_s,CLK_n) -- 0247a
begin
if Reset_s = '0' then
Req_Inhibit <= '0';
elsif CLK_n'event and CLK_n = '1' then
if MCycle = "001" and TState = "010" and wait_s = '1' then
Req_Inhibit <= '1';
else
Req_Inhibit <= '0';
end if;
end if;
end process;
-- Generate MReq_Inhibit
process (Reset_s, CLK_n)
begin
if Reset_s = '0' then
MReq_Inhibit <= '1'; -- Charlie Ingley 30/10/19 - changed Req_Inhibit polarity
elsif CLK_n'event and CLK_n = '0' then
if MCycle = "001" and TState = "010" and WAIT_n = '1' then -- by Fabio Belavenuto - fix behavior of Wait_n
MReq_Inhibit <= '0';
else
MReq_Inhibit <= '1';
end if;
end if;
end process;
process (Reset_s,CLK_n)
begin
if Reset_s = '0' then
MReq_Inhibit <= '0';
elsif CLK_n'event and CLK_n = '0' then
if MCycle = "001" and TState = "010" then
MReq_Inhibit <= '1';
else
MReq_Inhibit <= '0';
end if;
end if;
end process;
-- Generate RD for MREQ
process(Reset_s,CLK_n)
begin
if Reset_s = '0' then
RD <= '0';
MREQ <= '0';
elsif CLK_n'event and CLK_n = '0' then
if MCycle = "001" then
if TState = "001" then
RD <= IntCycle_n;
MREQ <= IntCycle_n;
end if;
if TState = "011" then
RD <= '0';
MREQ <= '1';
end if;
if TState = "100" then
MREQ <= '0';
end if;
else
if TState = "001" and NoRead = '0' then
RD <= not Write;
MREQ <= not IORQ;
end if;
if TState = "011" then
RD <= '0';
MREQ <= '0';
end if;
end if;
end if;
end process;
process(Reset_s,CLK_n)
begin
if Reset_s = '0' then
RD <= '0';
IORQ_n_i <= '1';
MREQ <= '0';
elsif CLK_n'event and CLK_n = '0' then
-- 30/10/19 Charlie Ingley - Generate IORQ_int for IORQ interrupt timing control
process(Reset_s,CLK_n)
begin
if Reset_s = '0' then
IORQ_int <= '0';
elsif CLK_n'event and CLK_n = '1' then
if MCycle = "001" then
if TState = "001" then
IORQ_int <= not IntCycle_n;
end if;
if TState = "010" then
IORQ_int <= '0';
end if;
end if;
end if;
end process;
if MCycle = "001" then
if TState = "001" then
RD <= IntCycle_n;
MREQ <= IntCycle_n;
IORQ_n_i <= IntCycle_n;
end if;
if TState = "011" then
RD <= '0';
IORQ_n_i <= '1';
MREQ <= '1';
end if;
if TState = "100" then
MREQ <= '0';
end if;
else
if TState = "001" and NoRead = '0' then
IORQ_n_i <= not IORQ;
MREQ <= not IORQ;
if IORQ = '0' then
RD <= not Write;
elsif IORQ_n_i = '0' then
RD <= not Write;
end if;
end if;
if TState = "011" then
RD <= '0';
IORQ_n_i <= '1';
MREQ <= '0';
end if;
end if;
end if;
end process;
process(Reset_s,CLK_n)
begin
if Reset_s = '0' then
IORQ_int_inhibit <= "111";
elsif CLK_n'event and CLK_n = '0' then
if IntCycle_n = '0' then
if MCycle = "001" then
IORQ_int_inhibit <= IORQ_int_inhibit(1 downto 0) & '0';
end if;
if MCycle = "010" then
IORQ_int_inhibit <= "111";
end if;
end if;
end if;
end process;
-- 30/10/19 Charlie Ingley - Generate IORQ_t1 for IORQ timing control
process(Reset_s, CLK_n)
begin
if Reset_s = '0' then
IORQ_t1 <= '1'
elsif CLK_n'event and CLK_n = '0' then
if TState = "001" then
IORQ_t1 <= not IntCycle_n;
end if;
if TState = "011" then
IORQ_t1 <= '1';
end if;
end if;
end process;
-- 30/10/19 Charlie Ingley - Generate IORQ_t2 for IORQ timing control
process (RESET_n, CLK_n)
begin
if RESET_n = '0' then
IORQ_t2 <= '1';
elsif CLK_n'event and CLK_n = '1' then
IORQ_t2 <= IORQ_t1;
end if;
end process;
end;