--===========================================================================----
--
-- S Y N T H E Z I A B L E System09 - SOC.
--
-- www.OpenCores.Org - September 2003
-- This core adheres to the GNU public license
--
-- File name : System09.vhd
--
-- Purpose : Top level file for 6809 compatible system on a chip
-- Designed with Xilinx XC3S200 Spartan 3 FPGA.
-- Implemented With Digilent Xilinx Starter FPGA board,
--
-- Dependencies : ieee.Std_Logic_1164
-- ieee.std_logic_unsigned
-- ieee.std_logic_arith
-- ieee.numeric_std
--
-- Uses : mon_rom (sys09bug_rom4k_b16.vhd) Monitor ROM
-- cpu09 (cpu09.vhd) CPU core
-- dat_ram (datram.vhd) Dynamic Address Translation
-- acia_6850 (acia_6850.vhd) ACIA (UART)
-- (acia_rx.vhd)
-- (acia_tx.vhd)
-- keyboard (keyboard.vhd) PS/2 Keyboard
-- (ps2_keyboard.vhd)
-- (keymap_rom)
-- vdu8 (vdu8.vhd) Video Display Unit
-- (char_rom2K_b16.vhd)
-- (ram2k_b16.vhd)
-- seven_segment (SevenSegment.vhd) Seven Segment Display
--
-- Author : John E. Kent
-- dilbert57@opencores.org
--
--===========================================================================----
--
-- Revision History:
--===========================================================================--
-- Version 0.1 - 20 March 2003
-- Version 0.2 - 30 March 2003
-- Version 0.3 - 29 April 2003
-- Version 0.4 - 29 June 2003
--
-- Version 0.5 - 19 July 2003
-- prints out "Hello World"
--
-- Version 0.6 - 5 September 2003
-- Runs SBUG
--
-- Version 1.0- 6 Sep 2003 - John Kent
-- Inverted sys_clk
-- Initial release to Open Cores
--
-- Version 1.1 - 17 Jan 2004 - John Kent
-- Updated miniUart.
--
-- Version 1.2 - 25 Jan 2004 - John Kent
-- removed signals "test_alu" and "test_cc"
-- Trap hardware re-instated.
--
-- Version 1.3 - 11 Feb 2004 - John Kent
-- Designed forked off to produce System09_VDU
-- Added VDU component
-- VDU runs at 25MHz and divides the clock by 2 for the CPU
-- UART Runs at 57.6 Kbps
--
-- Version 2.0 - 2 September 2004 - John Kent
-- ported to Digilent Xilinx Spartan3 starter board
-- removed Compaact Flash and Trap Logic.
-- Replaced SBUG with KBug9s
--
-- Version 2.1 - 21 November 2006 - John Kent
-- Replaced KBug9s with Sys09bug 1.0
-- Inverted bottom nybble of DAT register outputs
-- Changed ROM & I/O decoding to be compatible with SWTPc
-- Upped the serial baud rate to 115.2 KBd
-- added multiple global clock buffers
-- (Uart would not operate correctly)
--
-- Version 2.2 - 22 December 2006 - John Kent
-- Increased CPU clock from 12.5MHz to 25 MHz.
-- Removed some of the global clock buffers
-- Added LED output register
-- Changed address decoding to 4K Blocks
--
-- Version 2.3 - 1 June 2007 - John Kent
-- Updated VDU & ACIA
-- Changed decoding for Sys09Bug
--
-- Version 2.4 - 31 January 2008 - John Kent
-- ACIA does not appear to work.
-- Made RAM OE and WE strobes synchonous to sys_clk
--
--===========================================================================--
library ieee;
use ieee.std_logic_1164.all;
use IEEE.STD_LOGIC_ARITH.ALL;
use IEEE.STD_LOGIC_UNSIGNED.ALL;
use ieee.numeric_std.all;
entity my_system09 is
port(
sys_clk : in Std_Logic; -- System Clock input
rst_sw : in Std_logic; -- Master Reset input (active high)
nmi_sw : in Std_logic;
-- Memory Interface signals
ram_addr : out Std_Logic_Vector(17 downto 0);
ram_wen : out Std_Logic;
ram_oen : out Std_Logic;
ram1_cen : out Std_Logic;
ram1_ubn : out Std_Logic;
ram1_lbn : out Std_Logic;
ram1_data : inout Std_Logic_Vector(15 downto 0);
ram2_cen : out Std_Logic;
ram2_ubn : out Std_Logic;
ram2_lbn : out Std_Logic;
ram2_data : inout Std_Logic_Vector(15 downto 0);
-- PS/2 Keyboard
ps2c : inout Std_logic;
ps2d : inout Std_Logic;
-- ACIA Interface
rxd : in Std_Logic;
txd : out Std_Logic;
-- CRTC output signals
vs : out Std_Logic;
hs : out Std_Logic;
blue : out std_logic;
green : out std_logic;
red : out std_logic;
-- LEDS & Switches
leds : out std_logic_vector(7 downto 0);
switches : in std_logic_vector(7 downto 0);
-- seven segment display
segments : out std_logic_vector(7 downto 0);
digits : out std_logic_vector(3 downto 0)
);
end my_system09;
-------------------------------------------------------------------------------
-- Architecture for System09
-------------------------------------------------------------------------------
architecture my_computer of my_system09 is
-----------------------------------------------------------------------------
-- constants
-----------------------------------------------------------------------------
constant SYS_Clock_Frequency : integer := 100000000; -- FPGA System Clock
constant VGA_Clock_Frequency : integer := 25000000; -- VGA Pixel Clock
constant CPU_Clock_Frequency : integer := 25000000; -- CPU Clock
constant BAUD_Rate : integer := 57600; -- Baud Rate
constant ACIA_Clock_Frequency : integer := BAUD_Rate * 16;
type hold_state_type is ( hold_release_state, hold_request_state );
-----------------------------------------------------------------------------
-- Signals
-----------------------------------------------------------------------------
-- BOOT ROM
signal rom_cs : Std_logic;
signal rom_data_out : Std_Logic_Vector(7 downto 0);
-- FLEX9 RAM
signal flex_cs : Std_logic;
signal flex_data_out : Std_Logic_Vector(7 downto 0);
-- ACIA Interface signals
signal acia_clk : std_logic;
signal acia_data_out : Std_Logic_Vector(7 downto 0);
signal acia_cs : Std_Logic;
signal acia_irq : Std_Logic;
signal acia_rxd : Std_Logic;
signal acia_txd : Std_Logic;
signal acia_dcd_n : Std_Logic;
-- signal acia_rts_n : Std_Logic;
signal acia_cts_n : Std_Logic;
-- keyboard port
signal keyboard_data_out : std_logic_vector(7 downto 0);
signal keyboard_cs : std_logic;
signal keyboard_irq : std_logic;
-- LEDs
signal leds_data_out : std_logic_vector(7 downto 0);
signal leds_cs : std_logic;
-- RAM
signal ram_cs : std_logic; -- memory chip select
signal ram_data_out : std_logic_vector(7 downto 0);
signal ram1_ce : std_logic;
signal ram1_ub : std_logic;
signal ram1_lb : std_logic;
signal ram2_ce : std_logic;
signal ram2_ub : std_logic;
signal ram2_lb : std_logic;
signal ram_we : std_logic;
signal ram_oe : std_logic;
-- CPU Interface signals
signal cpu_reset : Std_Logic;
signal cpu_clk : Std_Logic;
signal cpu_rw : std_logic;
signal cpu_vma : std_logic;
signal cpu_halt : std_logic;
signal cpu_hold : std_logic;
signal cpu_firq : std_logic;
signal cpu_irq : std_logic;
signal cpu_nmi : std_logic;
signal cpu_addr : std_logic_vector(15 downto 0);
signal cpu_data_in : std_logic_vector(7 downto 0);
signal cpu_data_out : std_logic_vector(7 downto 0);
-- Dynamic Address Translation
signal dat_cs : std_logic;
signal dat_addr : std_logic_vector(7 downto 0);
-- Video Display Unit
signal vdu_cs : std_logic;
signal vdu_data_out : std_logic_vector(7 downto 0);
signal vga_clk : std_logic;
-- 7 Segment Display
signal seg_cs : std_logic;
signal seg_data_out : std_logic_vector(7 downto 0);
-- System Clock Prescaler
signal clk_count : std_logic;
signal Clk50 : std_logic;
-----------------------------------------------------------------
--
-- CPU09 CPU core
--
-----------------------------------------------------------------
component cpu09
port (
clk : in std_logic;
rst : in std_logic;
rw : out std_logic; -- Asynchronous memory interface
vma : out std_logic;
address : out std_logic_vector(15 downto 0);
data_in : in std_logic_vector(7 downto 0);
data_out : out std_logic_vector(7 downto 0);
halt : in std_logic;
hold : in std_logic;
irq : in std_logic;
nmi : in std_logic;
firq : in std_logic
);
end component;
----------------------------------------
--
-- 4KByte Block RAM Monitor ROM
--
----------------------------------------
component mon_rom
Port (
clk : in std_logic;
rst : in std_logic;
cs : in std_logic;
rw : in std_logic;
addr : in std_logic_vector (11 downto 0);
rdata : out std_logic_vector (7 downto 0);
wdata : in std_logic_vector (7 downto 0)
);
end component;
----------------------------------------
--
-- 8KBytes Block RAM for FLEX9
-- $C000 - $DFFF
--
----------------------------------------
component flex_ram
Port (
clk : in std_logic;
rst : in std_logic;
cs : in std_logic;
rw : in std_logic;
addr : in std_logic_vector (12 downto 0);
rdata : out std_logic_vector (7 downto 0);
wdata : in std_logic_vector (7 downto 0)
);
end component;
----------------------------------------
--
-- Dynamic Address Translation Registers
--
----------------------------------------
component dat_ram
port (
clk : in std_logic;
rst : in std_logic;
cs : in std_logic;
rw : in std_logic;
addr_lo : in std_logic_vector(3 downto 0);
addr_hi : in std_logic_vector(3 downto 0);
data_in : in std_logic_vector(7 downto 0);
data_out : out std_logic_vector(7 downto 0)
);
end component;
-----------------------------------------------------------------
--
-- 6850 ACIA
--
-----------------------------------------------------------------
component ACIA_6850
port (
clk : in Std_Logic; -- System Clock
rst : in Std_Logic; -- Reset input (active high)
cs : in Std_Logic; -- ACIA Chip Select
rw : in Std_Logic; -- Read / Not Write
irq : out Std_Logic; -- Interrupt
Addr : in Std_Logic; -- Register Select
DataIn : in Std_Logic_Vector(7 downto 0); -- Data Bus In
DataOut : out Std_Logic_Vector(7 downto 0); -- Data Bus Out
RxC : in Std_Logic; -- Receive Baud Clock
TxC : in Std_Logic; -- Transmit Baud Clock
RxD : in Std_Logic; -- Receive Data
TxD : out Std_Logic; -- Transmit Data
DCD_n : in Std_Logic; -- Data Carrier Detect
CTS_n : in Std_Logic; -- Clear To Send
RTS_n : out Std_Logic -- Request To send
);
end component;
-----------------------------------------------------------------
--
-- ACIA Clock divider
--
-----------------------------------------------------------------
component ACIA_Clock
generic (
SYS_Clock_Frequency : integer := SYS_Clock_Frequency;
ACIA_Clock_Frequency : integer := ACIA_Clock_Frequency
);
port (
clk : in Std_Logic; -- System Clock Input
ACIA_clk : out Std_logic -- ACIA Clock output
);
end component;
----------------------------------------
--
-- PS/2 Keyboard
--
----------------------------------------
component keyboard
generic(
KBD_Clock_Frequency : integer := CPU_Clock_Frequency
);
port(
clk : in std_logic;
rst : in std_logic;
cs : in std_logic;
rw : in std_logic;
addr : in std_logic;
data_in : in std_logic_vector(7 downto 0);
data_out : out std_logic_vector(7 downto 0);
irq : out std_logic;
kbd_clk : inout std_logic;
kbd_data : inout std_logic
);
end component;
----------------------------------------
--
-- Video Display Unit.
--
----------------------------------------
component vdu8
generic(
VDU_CLOCK_FREQUENCY : integer := CPU_Clock_Frequency; -- HZ
VGA_CLOCK_FREQUENCY : integer := VGA_Clock_Frequency; -- HZ
VGA_HOR_CHARS : integer := 80; -- CHARACTERS
VGA_VER_CHARS : integer := 25; -- CHARACTERS
VGA_PIXELS_PER_CHAR : integer := 8; -- PIXELS
VGA_LINES_PER_CHAR : integer := 16; -- LINES
VGA_HOR_BACK_PORCH : integer := 40; -- PIXELS
VGA_HOR_SYNC : integer := 96; -- PIXELS
VGA_HOR_FRONT_PORCH : integer := 24; -- PIXELS
VGA_VER_BACK_PORCH : integer := 13; -- LINES
VGA_VER_SYNC : integer := 1; -- LINES
VGA_VER_FRONT_PORCH : integer := 36 -- LINES
);
port(
-- control register interface
vdu_clk : in std_logic; -- CPU Clock - 12.5MHz
vdu_rst : in std_logic;
vdu_cs : in std_logic;
vdu_rw : in std_logic;
vdu_addr : in std_logic_vector(2 downto 0);
vdu_data_in : in std_logic_vector(7 downto 0);
vdu_data_out : out std_logic_vector(7 downto 0);
-- vga port connections
vga_clk : in std_logic; -- VGA Pixel Clock - 25 MHz
vga_red_o : out std_logic;
vga_green_o : out std_logic;
vga_blue_o : out std_logic;
vga_hsync_o : out std_logic;
vga_vsync_o : out std_logic
);
end component;
----------------------------------------
--
-- Seven Segment Display driver
--
----------------------------------------
component seven_segment is
port (
clk : in std_logic;
rst : in std_logic;
cs : in std_logic;
rw : in std_logic;
addr : in std_logic_vector(1 downto 0);
data_in : in std_logic_vector(7 downto 0);
data_out : out std_logic_vector(7 downto 0);
segments : out std_logic_vector(7 downto 0);
digits : out std_logic_vector(3 downto 0)
);
end component;
component BUFG
port (
i : in std_logic;
o : out std_logic
);
end component;
begin
-----------------------------------------------------------------------------
-- Instantiation of internal components
-----------------------------------------------------------------------------
my_cpu : cpu09 port map (
clk => cpu_clk,
rst => cpu_reset,
rw => cpu_rw,
vma => cpu_vma,
address => cpu_addr(15 downto 0),
data_in => cpu_data_in,
data_out => cpu_data_out,
halt => cpu_halt,
hold => cpu_hold,
irq => cpu_irq,
nmi => cpu_nmi,
firq => cpu_firq
);
my_rom : mon_rom port map (
clk => cpu_clk,
rst => cpu_reset,
cs => rom_cs,
rw => '1',
addr => cpu_addr(11 downto 0),
rdata => rom_data_out,
wdata => cpu_data_out
);
my_flex : flex_ram port map (
clk => cpu_clk,
rst => cpu_reset,
cs => flex_cs,
rw => cpu_rw,
addr => cpu_addr(12 downto 0),
rdata => flex_data_out,
wdata => cpu_data_out
);
my_dat : dat_ram port map (
clk => cpu_clk,
rst => cpu_reset,
cs => dat_cs,
rw => cpu_rw,
addr_hi => cpu_addr(15 downto 12),
addr_lo => cpu_addr(3 downto 0),
data_in => cpu_data_out,
data_out => dat_addr(7 downto 0)
);
my_acia : ACIA_6850 port map (
clk => cpu_clk,
rst => cpu_reset,
cs => acia_cs,
rw => cpu_rw,
irq => acia_irq,
Addr => cpu_addr(0),
Datain => cpu_data_out,
DataOut => acia_data_out,
RxC => acia_clk,
TxC => acia_clk,
RxD => acia_rxd,
TxD => acia_txd,
DCD_n => acia_dcd_n,
CTS_n => acia_cts_n,
RTS_n => open
);
----------------------------------------
--
-- ACIA Clock
--
----------------------------------------
my_ACIA_Clock : ACIA_Clock
generic map(
SYS_Clock_Frequency => SYS_Clock_Frequency,
ACIA_Clock_Frequency => ACIA_Clock_Frequency
)
port map(
clk => sys_clk,
acia_clk => acia_clk
);
----------------------------------------
--
-- PS/2 Keyboard Interface
--
----------------------------------------
my_keyboard : keyboard
generic map (
KBD_Clock_Frequency => CPU_Clock_frequency
)
port map(
clk => cpu_clk,
rst => cpu_reset,
cs => keyboard_cs,
rw => cpu_rw,
addr => cpu_addr(0),
data_in => cpu_data_out(7 downto 0),
data_out => keyboard_data_out(7 downto 0),
irq => keyboard_irq,
kbd_clk => ps2c,
kbd_data => ps2d
);
----------------------------------------
--
-- Video Display Unit instantiation
--
----------------------------------------
my_vdu : vdu8
generic map(
VDU_CLOCK_FREQUENCY => CPU_Clock_Frequency, -- HZ
VGA_CLOCK_FREQUENCY => VGA_Clock_Frequency, -- HZ
VGA_HOR_CHARS => 80, -- CHARACTERS
VGA_VER_CHARS => 25, -- CHARACTERS
VGA_PIXELS_PER_CHAR => 8, -- PIXELS
VGA_LINES_PER_CHAR => 16, -- LINES
VGA_HOR_BACK_PORCH => 40, -- PIXELS
VGA_HOR_SYNC => 96, -- PIXELS
VGA_HOR_FRONT_PORCH => 24, -- PIXELS
VGA_VER_BACK_PORCH => 13, -- LINES
VGA_VER_SYNC => 1, -- LINES
VGA_VER_FRONT_PORCH => 36 -- LINES
)
port map(
-- Control Registers
vdu_clk => cpu_clk, -- 12.5 MHz System Clock in
vdu_rst => cpu_reset,
vdu_cs => vdu_cs,
vdu_rw => cpu_rw,
vdu_addr => cpu_addr(2 downto 0),
vdu_data_in => cpu_data_out,
vdu_data_out => vdu_data_out,
-- vga port connections
vga_clk => vga_clk, -- 25 MHz VDU pixel clock
vga_red_o => red,
vga_green_o => green,
vga_blue_o => blue,
vga_hsync_o => hs,
vga_vsync_o => vs
);
----------------------------------------
--
-- Seven Segment Display instantiation
--
----------------------------------------
my_seg : seven_segment port map (
clk => cpu_clk,
rst => cpu_reset,
cs => seg_cs,
rw => cpu_rw,
addr => cpu_addr(1 downto 0),
data_in => cpu_data_out,
data_out => seg_data_out,
segments => segments,
digits => digits
);
vga_clk_buffer : BUFG port map(
i => clk_count,
o => vga_clk
);
cpu_clk_buffer : BUFG port map(
i => clk_count,
o => cpu_clk
);
clk50_clock : process( sys_clk, Clk50 )
begin
if sys_clk'event and sys_clk='1' then
Clk50 <= not Clk50;
end if;
end process;
--
-- Clock divider
-- Assumes 50 MHz system clock
-- 25MHz pixel clock
-- 25MHz CPU clock
--
sys09_clock : process( Clk50, clk_count )
begin
if Clk50'event and CLk50='1' then
clk_count <= not clk_count;
end if;
end process;
----------------------------------------------------------------------
--
-- Process to decode memory map
--
----------------------------------------------------------------------
mem_decode: process( cpu_addr, cpu_rw, cpu_vma,
dat_cs, dat_addr,
rom_data_out,
acia_data_out,
keyboard_data_out,
vdu_data_out,
seg_data_out,
leds_data_out,
flex_data_out,
ram_data_out
)
begin
cpu_data_in <= (others=>'0');
dat_cs <= '0';
rom_cs <= '0';
acia_cs <= '0';
keyboard_cs <= '0';
vdu_cs <= '0';
seg_cs <= '0';
leds_cs <= '0';
flex_cs <= '0';
ram_cs <= '0';
-- timer_cs <= '0';
-- trap_cs <= '0';
-- pb_cs <= '0';
-- ide_cs <= '0';
-- ether_cs <= '0';
-- slot1_cs <= '0';
-- slot2_cs <= '0';
if cpu_addr( 15 downto 8 ) = "11111111" then
cpu_data_in <= rom_data_out;
dat_cs <= cpu_vma; -- write DAT
rom_cs <= cpu_vma; -- read ROM
--
-- Sys09Bug Monitor ROM $F000 - $FFFF
--
elsif dat_addr(3 downto 0) = "1111" then -- $XF000 - $XFFFF
--
-- Monitor ROM $F000 - $FFFF
--
cpu_data_in <= rom_data_out;
rom_cs <= cpu_vma; -- read ROM
--
-- IO Devices $E000 - $EFFF
--
elsif dat_addr(3 downto 0) = "1110" then -- $XE000 - $XEFFF
case cpu_addr(11 downto 8) is
--
-- SWTPC peripherals from $E000 to $E0FF
--
when "0000" =>
case cpu_addr(7 downto 4) is
--
-- ACIA ($E000 - $E00F)
--
when "0000" =>
cpu_data_in <= acia_data_out;
acia_cs <= cpu_vma;
--
-- Reserved - FD1771 FDC ($E010 - $E01F) (SWTPC)
--
--
-- Keyboard port ($E020 - $E02F)
--
when "0010" =>
cpu_data_in <= keyboard_data_out;
keyboard_cs <= cpu_vma;
--
-- VDU port ($E030 - $E03F)
--
when "0011" =>
cpu_data_in <= vdu_data_out;
vdu_cs <= cpu_vma;
--
-- Reserved - SWTPc MP-T ($E040 - $E04F)
--
--
-- Reserved - Timer ($E050 - $E05F) (B5-X300)
--
--
-- Reserved - Bus Trap Logic ($E060 - $E06F) (B5-X300)
--
--
-- Reserved - I/O port ($E070 - $E07F) (B5-X300)
--
--
-- Reserved - PTM 6840 ($E080 - $E08F) (SWTPC)
--
--
-- Reserved - PIA Timer ($E090 - $E09F) (SWTPC)
--
--
-- Read Switched port ($E0A0 - $E0AF)
-- Write LEDS
--
when "1010" =>
cpu_data_in <= leds_data_out;
leds_cs <= cpu_vma;
--
-- 7 segment display port ($E0B0 - $E0BF)
--
when "1011" =>
cpu_data_in <= seg_data_out;
seg_cs <= cpu_vma;
when others => -- $EXC0 to $EXFF
null;
end case;
--
-- XST-3.0 Peripheral Bus goes here
-- $E100 to $E1FF
-- Four devices
-- IDE, Ethernet, Slot1, Slot2
--
-- when "0001" =>
-- cpu_data_in <= pb_data_out;
-- pb_cs <= cpu_vma;
-- case cpu_addr(7 downto 6) is
--
-- IDE Interface $E100 to $E13F
--
-- when "00" =>
-- ide_cs <= cpu_vma;
--
-- Ethernet Interface $E140 to $E17F
--
-- when "01" =>
-- ether_cs <= cpu_vma;
--
-- Slot 1 Interface $E180 to $E1BF
--
-- when "10" =>
-- slot1_cs <= cpu_vma;
--
-- Slot 2 Interface $E1C0 to $E1FF
--
-- when "11" =>
-- slot2_cs <= cpu_vma;
--
-- Nothing else
--
-- when others =>
-- null;
-- end case;
--
-- $E200 to $EFFF reserved for future use
--
when others =>
null;
end case;
--
-- FLEX RAM $0C000 - $0DFFF
--
elsif dat_addr(7 downto 1) = "0000110" then -- $0C000 - $0DFFF
cpu_data_in <= flex_data_out;
flex_cs <= cpu_vma;
--
-- Everything else is RAM
--
else
cpu_data_in <= ram_data_out;
ram_cs <= cpu_vma;
end if;
end process;
--
-- 1M byte SRAM Control
-- Processes to read and write memory based on bus signals
--
ram_process: process( cpu_reset, sys_clk,
cpu_addr, cpu_rw, cpu_vma, cpu_data_out,
dat_addr, ram_cs,
ram1_ce, ram1_ub, ram1_lb, ram1_data,
ram2_ce, ram2_ub, ram2_lb, ram2_data,
ram_we, ram_oe )
begin
--
-- ram_hold signal helps
--
if( cpu_reset = '1' ) then
ram_we <= '0';
ram_oe <= '0';
--
-- Clock Hold on rising edge
--
elsif( sys_clk'event and sys_clk='1' ) then
if (ram_cs = '1') and (ram_we = '0') and (ram_oe = '0') then
ram_we <= not cpu_rw;
ram_oe <= cpu_rw;
else
ram_we <= '0';
ram_oe <= '0';
end if;
end if;
ram_wen <= not ram_we;
ram_oen <= not ram_oe;
ram1_ce <= ram_cs and (not cpu_addr(1));
ram1_ub <= not cpu_addr(0);
ram1_lb <= cpu_addr(0);
ram1_cen <= not ram1_ce;
ram1_ubn <= not ram1_ub;
ram1_lbn <= not ram1_lb;
ram2_ce <= ram_cs and cpu_addr(1);
ram2_ub <= not cpu_addr(0);
ram2_lb <= cpu_addr(0);
ram2_cen <= not ram2_ce;
ram2_ubn <= not ram2_ub;
ram2_lbn <= not ram2_lb;
ram_addr(17 downto 10) <= dat_addr(7 downto 0);
ram_addr(9 downto 0) <= cpu_addr(11 downto 2);
if ram_we = '1' and ram1_ce = '1' and ram1_lb = '1' then
ram1_data(7 downto 0) <= cpu_data_out;
else
ram1_data(7 downto 0) <= "ZZZZZZZZ";
end if;
if ram_we = '1' and ram1_ce = '1' and ram1_ub = '1' then
ram1_data(15 downto 8) <= cpu_data_out;
else
ram1_data(15 downto 8) <= "ZZZZZZZZ";
end if;
if ram_we = '1' and ram2_ce = '1' and ram2_lb = '1' then
ram2_data(7 downto 0) <= cpu_data_out;
else
ram2_data(7 downto 0) <= "ZZZZZZZZ";
end if;
if ram_we = '1' and ram2_ce = '1' and ram2_ub = '1' then
ram2_data(15 downto 8) <= cpu_data_out;
else
ram2_data(15 downto 8) <= "ZZZZZZZZ";
end if;
case cpu_addr(1 downto 0) is
when "00" =>
ram_data_out <= ram1_data(15 downto 8);
when "01" =>
ram_data_out <= ram1_data(7 downto 0);
when "10" =>
ram_data_out <= ram2_data(15 downto 8);
when others =>
ram_data_out <= ram2_data(7 downto 0);
end case;
end process;
--
-- LEDS output register
--
leds_output : process( cpu_clk, cpu_reset, switches )
begin
if cpu_reset = '1' then
leds <= "00000000";
elsif cpu_clk'event and cpu_clk='0' then
if leds_cs = '1' and cpu_rw = '0' then
leds <= cpu_data_out;
end if;
end if;
leds_data_out <= switches;
end process;
--
-- Interrupts and other bus control signals
--
interrupts : process( rst_sw,
acia_irq,
keyboard_irq,
nmi_sw
)
begin
if sys_clk'event and sys_clk = '1' then
cpu_reset <= rst_sw; -- CPU reset is active high
end if;
cpu_firq <= keyboard_irq;
cpu_nmi <= nmi_sw;
cpu_irq <= acia_irq;
cpu_halt <= '0';
cpu_hold <= '0';
end process;
--
-- ACIA pin assignments
--
acia_assignments : process( rxd, acia_txd )
begin
acia_dcd_n <= '0';
acia_cts_n <= '0';
acia_rxd <= rxd;
txd <= acia_txd;
end process;
end my_computer; --===================== End of architecture =======================--
Error running this command: diff -w -U 5 "/tmp/7TQ1Cs" ""
diff: : No such file or directory