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URL https://opencores.org/ocsvn/System09/System09/trunk

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    /System09/trunk
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Rev 140 → Rev 139

/rtl/System09_base/system09.vhd
203,7 → 203,7
-- Slot 2 $E1C0 - $E1FF
slot2_cs_n : out std_logic;
-- slot2_irq : in std_logic;
 
 
-- CPU Debug Interface signals
-- cpu_reset_o : out Std_Logic;
-- cpu_clk_o : out Std_Logic;
230,8 → 230,8
 
-----------------------------------------------------------------------------
-- constants
-----------------------------------------------------------------------------
 
-----------------------------------------------------------------------------
 
-- SDRAM
constant MEM_CLK_FREQ : natural := 100_000; -- operating frequency of Memory in KHz
constant SYS_CLK_DIV : real := 2.0; -- divisor for FREQ (can only be 1.0, 1.5, 2.0, 2.5, 3.0, 4.0, 5.0, 8.0 or 16.0)
245,14 → 245,14
constant SADDR_WIDTH : natural := 13; -- SDRAM-side address width
 
constant SYS_CLK_FREQ : natural := ((MEM_CLK_FREQ*2)/integer(SYS_CLK_DIV*2.0))*1000; -- FPGA System Clock
constant CPU_CLK_FREQ : natural := 25_000_000; -- CPU Clock (Hz)
constant CPU_CLK_FREQ : natural := 25_000_000; -- CPU Clock (Hz)
constant CPU_CLK_DIV : natural := (SYS_CLK_FREQ/CPU_CLK_FREQ);
constant VGA_CLK_FREQ : natural := 25_000_000; -- VGA Pixel Clock
constant VGA_CLK_DIV : natural := ((MEM_CLK_FREQ*1000)/VGA_CLK_FREQ);
constant BAUD_RATE : integer := 57600; -- Baud Rate
constant ACIA_CLK_FREQ : integer := BAUD_RATE * 16;
 
constant TRESET : natural := 300; -- min initialization interval (us)
constant ACIA_CLK_FREQ : integer := BAUD_RATE * 16;
 
constant TRESET : natural := 300; -- min initialization interval (us)
constant RST_CYCLES : natural := 1+(TRESET*(MEM_CLK_FREQ/1_000)); -- SDRAM power-on initialization interval
 
type hold_state_type is ( hold_release_state, hold_request_state );
362,16 → 362,16
signal hDOut : std_logic_vector(DATA_WIDTH-1 downto 0); -- host-side data from SDRAM
signal hRd : std_logic; -- host-side read control signal
signal hWr : std_logic; -- host-side write control signal
signal hUds : std_logic; -- host-side upper data strobe
signal hLds : std_logic; -- host-side lower data strobe
signal hUds : std_logic; -- host-side upper data strobe
signal hLds : std_logic; -- host-side lower data strobe
signal rdPending : std_logic; -- read operation pending in SDRAM pipeline
type ram_type is (ram_state_0,
ram_state_rd1, ram_state_rd2,
ram_state_wr1,
type ram_type is (ram_state_0,
ram_state_rd1, ram_state_rd2,
ram_state_wr1,
ram_state_3 );
signal ram_state : ram_type;
 
 
 
-- signal BaudCount : std_logic_vector(5 downto 0);
signal CountL : std_logic_vector(23 downto 0);
signal clk_count : natural range 0 to CPU_CLK_DIV;
604,8 → 604,8
data_out : out std_logic_vector(7 downto 0)
);
end component;
 
 
 
component XSASDRAMCntl
generic(
FREQ : natural := MEM_CLK_FREQ;-- operating frequency in KHz
629,8 → 629,8
rst : in std_logic; -- reset
rd : in std_logic; -- initiate read operation
wr : in std_logic; -- initiate write operation
uds : in std_logic; -- upper data strobe
lds : in std_logic; -- lower data strobe
uds : in std_logic; -- upper data strobe
lds : in std_logic; -- lower data strobe
earlyOpBegun : out std_logic; -- read/write/self-refresh op begun (async)
opBegun : out std_logic; -- read/write/self-refresh op begun (clocked)
rdPending : out std_logic; -- read operation(s) are still in the pipeline
656,7 → 656,7
dqml : out std_logic -- low databits I/O mask
);
end component;
 
 
--
-- Clock buffer
--
842,7 → 842,7
data_in => cpu_data_out,
data_out => dat_addr(7 downto 0)
);
 
 
------------------------------------------------------------------------
-- Instantiate the SDRAM controller that connects to the memory tester
-- module and interfaces to the external SDRAM chip.
849,9 → 849,9
------------------------------------------------------------------------
u1 : xsaSDRAMCntl
generic map(
FREQ => MEM_CLK_FREQ,
FREQ => MEM_CLK_FREQ,
CLK_DIV => SYS_CLK_DIV,
PIPE_EN => PIPE_EN,
PIPE_EN => PIPE_EN,
MAX_NOP => MAX_NOP,
MULTIPLE_ACTIVE_ROWS => MULTIPLE_ACTIVE_ROWS,
DATA_WIDTH => DATA_WIDTH,
870,8 → 870,8
rst => rst_i, -- reset
rd => hRd, -- host-side SDRAM read control from memory tester
wr => hWr, -- host-side SDRAM write control from memory tester
uds => hUds, -- host-side SDRAM upper data strobe
lds => hLds, -- host-side SDRAM lower data strobe
uds => hUds, -- host-side SDRAM upper data strobe
lds => hLds, -- host-side SDRAM lower data strobe
rdPending => rdPending,-- read operation to SDRAM is in progress
opBegun => opBegun, -- indicates memory read/write has begun
earlyOpBegun => earlyBegun, -- early indicator that memory operation has begun
895,7 → 895,7
dqmh => SDRAM_dqmh, -- SDRAM DQMH
dqml => SDRAM_dqml -- SDRAM DQML
);
 
 
cpu_clk_buffer : BUFG port map(
i => Clk25,
o => cpu_clk
1085,7 → 1085,7
-- ISA bus little endian
-- Not sure about IDE interface
--
peripheral_bus: process( clk_i, cpu_reset, cpu_rw, cpu_addr, cpu_data_out,
peripheral_bus: process( clk_i, cpu_reset, cpu_rw, cpu_addr, cpu_data_out,
pb_cs, pb_wreg, pb_rreg )
begin
pb_wru <= pb_cs and (not cpu_rw) and (not cpu_addr(0));
1246,20 → 1246,20
my_prescaler : process( clk_i, clk_count )
begin
if rising_edge( clk_i ) then
 
if clk_count = 0 then
clk_count <= CPU_CLK_DIV-1;
else
clk_count <= clk_count - 1;
end if;
 
if clk_count = 0 then
clk_count <= CPU_CLK_DIV-1;
else
clk_count <= clk_count - 1;
if clk_count = 0 then
clk25 <= '0';
elsif clk_count = (CPU_CLK_DIV/2) then
clk25 <= '1';
end if;
 
if clk_count = 0 then
clk25 <= '0';
elsif clk_count = (CPU_CLK_DIV/2) then
clk25 <= '1';
end if;
 
end if;
 
end if;
end process;
 
--
1267,8 → 1267,8
--
my_switch_assignments : process( rst_i, SW2_N, lock )
begin
rst_i <= not SW2_N;
cpu_reset <= rst_i or (not lock);
rst_i <= not SW2_N;
cpu_reset <= rst_i or (not lock);
end process;
 
--
1317,7 → 1317,7
VGA_blue(1) <= vga_blue_o;
VGA_blue(2) <= vga_blue_o;
end process;
 
 
--
-- SDRAM read write control
--
1327,7 → 1327,7
ram_rd_req, ram_wr_req )
begin
if( cpu_reset = '1' ) then
hRd <= '0';
hRd <= '0';
hWr <= '0';
ram_hold <= '0';
ram_state <= ram_state_0;
1340,13 → 1340,13
 
when ram_state_0 =>
if ram_rd_req = '1' then
ram_hold <= '1';
ram_hold <= '1';
hRd <= '1';
ram_state <= ram_state_rd1;
elsif ram_wr_req = '1' then
ram_hold <= '1';
hWr <= '1';
ram_state <= ram_state_wr1;
ram_state <= ram_state_rd1;
elsif ram_wr_req = '1' then
ram_hold <= '1';
hWr <= '1';
ram_state <= ram_state_wr1;
end if;
 
when ram_state_rd1 =>
1357,13 → 1357,13
 
when ram_state_rd2 =>
if ramDone = '1' then
ram_hold <= '0';
ram_hold <= '0';
ram_state <= ram_state_3;
end if;
 
when ram_state_wr1 =>
if opBegun = '1' then
ram_hold <= '0';
ram_hold <= '0';
hWr <= '0';
ram_state <= ram_state_3;
end if;
1376,35 → 1376,35
when others =>
hRd <= '0';
hWr <= '0';
ram_hold <= '0';
ram_hold <= '0';
ram_state <= ram_state_0;
end case;
 
end if;
end process;
 
 
--
-- SDRAM Address and data bus assignments
--
-- SDRAM Address and data bus assignments
--
my_sdram_addr_data : process( cpu_addr, dat_addr,
cpu_data_out, hDout )
begin
hAddr(23 downto 19) <= "00000";
hAddr(18 downto 11) <= dat_addr;
hAddr(10 downto 0) <= cpu_addr(11 downto 1);
hUds <= not cpu_addr(0);
hLds <= cpu_addr(0);
if cpu_addr(0) = '0' then
hDin( 7 downto 0) <= (others=>'0');
hDin(15 downto 8) <= cpu_data_out;
ram_data_out <= hDout(15 downto 8);
else
hDin( 7 downto 0) <= cpu_data_out;
hDin(15 downto 8) <= (others=>'0');
ram_data_out <= hDout( 7 downto 0);
end if;
begin
hAddr(23 downto 19) <= "00000";
hAddr(18 downto 11) <= dat_addr;
hAddr(10 downto 0) <= cpu_addr(11 downto 1);
hUds <= not cpu_addr(0);
hLds <= cpu_addr(0);
if cpu_addr(0) = '0' then
hDin( 7 downto 0) <= (others=>'0');
hDin(15 downto 8) <= cpu_data_out;
ram_data_out <= hDout(15 downto 8);
else
hDin( 7 downto 0) <= cpu_data_out;
hDin(15 downto 8) <= (others=>'0');
ram_data_out <= hDout( 7 downto 0);
end if;
end process;
 
 
--
-- Hold RAM until falling CPU clock edge
--
1416,21 → 1416,21
ram_release <= '1';
end if;
end process;
 
 
--
-- CPU read data request on rising CPU clock edge
--
ram_read_request: process( hRd, cpu_clk, ram_cs, cpu_rw, ram_release )
begin
if hRd = '1' then
if hRd = '1' then
ram_rd_req <= '0';
elsif rising_edge(cpu_clk) then
elsif rising_edge(cpu_clk) then
if (ram_cs = '1') and (cpu_rw = '1') and (ram_release = '1') then
ram_rd_req <= '1';
end if;
ram_rd_req <= '1';
end if;
end if;
end process;
 
 
--
-- CPU write data to RAM valid on rising CPU clock edge
--
1438,43 → 1438,43
begin
if hWr = '1' then
ram_wr_req <= '0';
elsif rising_edge(cpu_clk) then
elsif rising_edge(cpu_clk) then
if (ram_cs = '1') and (cpu_rw = '0') and (ram_release = '1') then
ram_wr_req <= '1';
ram_wr_req <= '1';
end if;
end if;
end process;
 
 
 
status_leds : process( rst_i, cpu_reset, lock )
begin
S(0) <= rst_i;
S(1) <= cpu_reset;
S(2) <= lock;
S(3) <= countL(23);
S(7 downto 4) <= "0000";
end process;
 
--debug_proc : process( cpu_reset, cpu_clk, cpu_rw, cpu_vma,
-- cpu_halt, cpu_hold,
-- cpu_firq, cpu_irq, cpu_nmi,
-- cpu_addr, cpu_data_out, cpu_data_in )
--begin
-- cpu_reset_o <= cpu_reset;
-- cpu_clk_o <= cpu_clk;
-- cpu_rw_o <= cpu_rw;
-- cpu_vma_o <= cpu_vma;
-- cpu_halt_o <= cpu_halt;
-- cpu_hold_o <= cpu_hold;
-- cpu_firq_o <= cpu_firq;
-- cpu_irq_o <= cpu_irq;
-- cpu_nmi_o <= cpu_nmi;
-- cpu_addr_o <= cpu_addr;
-- cpu_data_out_o <= cpu_data_out;
-- cpu_data_in_o <= cpu_data_in;
--end process;
 
 
status_leds : process( rst_i, cpu_reset, lock )
begin
S(0) <= rst_i;
S(1) <= cpu_reset;
S(2) <= lock;
S(3) <= countL(23);
S(7 downto 4) <= "0000";
end process;
 
--debug_proc : process( cpu_reset, cpu_clk, cpu_rw, cpu_vma,
-- cpu_halt, cpu_hold,
-- cpu_firq, cpu_irq, cpu_nmi,
-- cpu_addr, cpu_data_out, cpu_data_in )
--begin
-- cpu_reset_o <= cpu_reset;
-- cpu_clk_o <= cpu_clk;
-- cpu_rw_o <= cpu_rw;
-- cpu_vma_o <= cpu_vma;
-- cpu_halt_o <= cpu_halt;
-- cpu_hold_o <= cpu_hold;
-- cpu_firq_o <= cpu_firq;
-- cpu_irq_o <= cpu_irq;
-- cpu_nmi_o <= cpu_nmi;
-- cpu_addr_o <= cpu_addr;
-- cpu_data_out_o <= cpu_data_out;
-- cpu_data_in_o <= cpu_data_in;
--end process;
 
 
end rtl; --===================== End of architecture =======================--
 
/rtl/System09_base/my_system09.vhd
0,0 → 1,1408
--===========================================================================----
--
-- S Y N T H E Z I A B L E System09 - SOC.
--
-- www.OpenCores.Org - February 2007
-- This core adheres to the GNU public license
--
-- File name : System09_Xess_XSA-3S1000.vhd
--
-- Purpose : Top level file for 6809 compatible system on a chip
-- Designed with Xilinx XC3S1000 Spartan 3 FPGA.
-- Implemented With XESS XSA-3S1000 FPGA board.
-- *** Note ***
-- This configuration can run Flex9 however it only has
-- 32k bytes of user memory and the VDU is monochrome
-- The design needs to be updated to use the SDRAM on
-- the XSA-3S1000 board.
-- This configuration also lacks a DAT so cannot use
-- the RAM Disk features of SYS09BUG.
--
-- Dependencies : ieee.Std_Logic_1164
-- ieee.std_logic_unsigned
-- ieee.std_logic_arith
-- ieee.numeric_std
-- unisim.vcomponents
--
-- Uses : mon_rom (sys09bug_rom4k_b16.vhd) Sys09Bug Monitor ROM
-- cpu09 (cpu09.vhd) CPU core
-- ACIA_6850 (ACIA_6850.vhd) ACIA / UART
-- (ACIA_RX.vhd)
-- (ACIA_TX.vhd)
-- ACIA_Clock (ACIA_Clock.vhd) ACIA clock.
-- keyboard (keyboard.vhd) PS/2 Keyboard interface
-- (ps2_keyboard.vhd)
-- (keymap_rom_slice.vhd) Key map table
-- vdu8_mono (vdu8_mono.vhd) Monochrome VDU
-- (char_rom2k_b16.vhd)
-- (ram2k_b16.vhd)
-- timer (timer.vhd) Interrupt timer
-- trap (trap.vhd) Bus condition trap logic
-- flex_ram (flex9_ram8k_b16.vhd) Flex operating system
-- ram_32K (ram32k_b16.vhd) 32 KBytes of Block RAM
--
--
-- Author : John E. Kent
-- dilbert57@opencores.org
--
-- Memory Map :
--
-- $0000 - User program RAM (32K Bytes)
-- $C000 - Flex Operating System memory (8K Bytes)
-- $E000 - ACIA (SWTPc)
-- $E010 - Reserved for FD1771 FDC (SWTPc)
-- $E020 - Keyboard
-- $E030 - VDU
-- $E040 - IDE / Compact Flash interface
-- $E050 - Timer
-- $E060 - Bus trap
-- $E070 - Reserced for Parallel I/O (B5-X300)
-- $E080 - Reserved for 6821 PIA (?) (SWTPc)
-- $E090 - Reserved for 6840 PTM (?) (SWTPc)
-- $F000 - Sys09Bug monitor Program (4K Bytes)
--
--===========================================================================----
--
-- 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 SysClk
-- 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 Compact Flash and Trap Logic.
-- Replaced SBUG with KBug9s
--
-- Version 3.0 - 29th August 2006 - John Kent
-- Adapted to XSA-3S1000 board.
-- Removed DAT and miniUART.
-- Used 32KBytes of Block RAM.
--
-- Version 3.1 - 15th January 2007 - John Kent
-- Modified vdu8 interface
-- Added a clock divider
--
-- Version 3.2 - 25th February 2007 - John Kent
-- reinstated ACIA_6850 and ACIA_Clock
-- Updated VDU8 & Keyboard with generic parameters
-- Defined Constants for clock speed calculations
--
-- Version 3.3 - 1st July 2007 - John Kent
-- Made VDU mono to save on one RAMB16
-- Used distributed memory for Key Map ROM to save one RAMB16
-- Added Flex RAM at $C000 to $DFFF using 4 spare RAMB16s
-- Added timer and trap logic
-- Added IDE Interface for Compact Flash
-- Replaced KBug9s and stack with Sys09Bug.
--
-- Version 4.0 - 1st February 2008 - John kent
-- Replaced Block RAM with SDRAM Interface
-- Modified Hold timing for SDRAM
-- Added CF and Ethernet interface
-- via the 16 bit peripheral bus at $E100
--
--===========================================================================--
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;
library work;
use work.common.all;
use WORK.xsasdram.all;
library unisim;
use unisim.vcomponents.all;
 
entity my_system09 is
port(
CLKA : in Std_Logic; -- 100MHz Clock input
SW2_N : in Std_logic; -- Master Reset input (active low)
SW3_N : in Std_logic; -- Non Maskable Interrupt input (active low)
 
-- PS/2 Keyboard
ps2_clk : inout Std_logic;
ps2_dat : inout Std_Logic;
 
-- CRTC output signals
vga_vsync_n : out Std_Logic;
vga_hsync_n : out Std_Logic;
vga_blue : out std_logic_vector(2 downto 0);
vga_green : out std_logic_vector(2 downto 0);
vga_red : out std_logic_vector(2 downto 0);
 
-- RS232 Port
RS232_RXD : in Std_Logic;
RS232_TXD : out Std_Logic;
RS232_CTS : in Std_Logic;
RS232_RTS : out Std_Logic;
 
-- Status 7 segment LED
-- S : out std_logic_vector(7 downto 0);
 
-- SDRAM side
SDRAM_clkfb : in std_logic; -- feedback SDRAM clock after PCB delays
SDRAM_clkout : out std_logic; -- clock to SDRAM
SDRAM_CKE : out std_logic; -- clock-enable to SDRAM
SDRAM_CS_N : out std_logic; -- chip-select to SDRAM
SDRAM_RAS_N : out std_logic; -- SDRAM row address strobe
SDRAM_CAS_N : out std_logic; -- SDRAM column address strobe
SDRAM_WE_N : out std_logic; -- SDRAM write enable
SDRAM_BA : out std_logic_vector(1 downto 0); -- SDRAM bank address
SDRAM_A : out std_logic_vector(12 downto 0); -- SDRAM row/column address
SDRAM_D : inout std_logic_vector(15 downto 0); -- data from SDRAM
SDRAM_DQMH : out std_logic; -- enable upper-byte of SDRAM databus if true
SDRAM_DQML : out std_logic; -- enable lower-byte of SDRAM databus if true
 
-- Peripheral I/O bus $E100 - $E1FF
PB_RD_N : out std_logic;
PB_WR_N : out std_logic;
PB_A : out std_logic_vector(4 downto 0);
PB_D : inout std_logic_vector(15 downto 0);
 
-- IDE Compact Flash $E100 - $E13F
ide_dmack_n : out std_logic;
ide_cs0_n : out std_logic;
ide_cs1_n : out std_logic;
 
-- Ethernet $E140 - $E17F
ether_cs_n : out std_logic;
ether_aen : out std_logic; -- Ethernet address enable not
ether_bhe_n : out std_logic; -- Ethernet bus high enable
ether_clk : in std_logic; -- Ethernet clock
ether_rdy : in std_logic; -- Ethernet ready
ether_irq : in std_logic; -- Ethernet irq - Shared with BAR6
 
-- Slot 1 $E180 - $E1BF
slot1_cs_n : out std_logic;
-- slot1_irq : in std_logic;
 
-- Slot 2 $E1C0 - $E1FF
slot2_cs_n : out std_logic;
-- slot2_irq : in std_logic;
-- Disable Flash
FLASH_CE_N : out std_logic
);
end My_System09;
 
-------------------------------------------------------------------------------
-- Architecture for System09
-------------------------------------------------------------------------------
architecture rtl of my_system09 is
 
-----------------------------------------------------------------------------
-- constants
-----------------------------------------------------------------------------
constant SYS_Clock_Frequency : integer := 50000000; -- FPGA System Clock
constant PIX_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
-----------------------------------------------------------------------------
signal rst_n : Std_logic; -- Master Reset input (active low)
signal nmi_n : Std_logic; -- Non Maskable Interrupt input (active low)
 
-- BOOT ROM
signal rom_cs : Std_logic;
signal rom_data_out : Std_Logic_Vector(7 downto 0);
 
-- Flex Memory & Monitor Stack
signal flex_cs : Std_logic;
signal flex_data_out : Std_Logic_Vector(7 downto 0);
 
-- ACIA/UART Interface signals
signal acia_data_out : Std_Logic_Vector(7 downto 0);
signal acia_cs : Std_Logic;
signal acia_irq : Std_Logic;
signal acia_clk : Std_Logic;
signal rxd : Std_Logic;
signal txd : Std_Logic;
signal DCD_n : Std_Logic;
signal RTS_n : Std_Logic;
signal 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;
 
-- RAM
signal ram_cs : std_logic; -- memory chip select
signal ram_data_out : std_logic_vector(7 downto 0);
signal ram_hold : std_logic; -- hold off slow accesses
 
-- 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_red_o : std_logic;
signal vga_green_o : std_logic;
signal vga_blue_o : std_logic;
 
-- timer
signal timer_data_out : std_logic_vector(7 downto 0);
signal timer_cs : std_logic;
signal timer_irq : std_logic;
 
-- trap
signal trap_cs : std_logic;
signal trap_data_out : std_logic_vector(7 downto 0);
signal trap_irq : std_logic;
 
-- Peripheral Bus port
signal pb_data_out : std_logic_vector(7 downto 0);
signal pb_cs : std_logic; -- peripheral bus chip select
signal pb_wru : std_logic; -- upper byte write strobe
signal pb_wrl : std_logic; -- lower byte write strobe
signal pb_rdu : std_logic; -- upper byte read strobe
signal pb_rdl : std_logic; -- lower byte read strobe
signal pb_hold : std_logic; -- hold peripheral bus access
signal pb_release : std_logic; -- release hold of peripheral bus
signal pb_count : std_logic_vector(3 downto 0); -- hold counter
signal pb_hold_state : hold_state_type;
signal pb_wreg : std_logic_vector(7 downto 0); -- lower byte write register
signal pb_rreg : std_logic_vector(7 downto 0); -- lower byte read register
 
-- Peripheral chip selects on Peripheral Bus
signal ide_cs : std_logic; -- IDE CF interface
signal ether_cs : std_logic; -- Ethernet interface
signal slot1_cs : std_logic; -- Expansion slot 1
signal slot2_cs : std_logic; -- Expansion slot 2
 
 
-- SDRAM
 
constant FREQ : natural := 100_000; -- operating frequency in KHz
constant CLK_DIV : real := 2.0; -- divisor for FREQ (can only be 1.0, 1.5, 2.0, 2.5, 3.0, 4.0, 5.0, 8.0 or 16.0)
constant PIPE_EN : boolean := false; -- if true, enable pipelined read operations
constant MAX_NOP : natural := 10000; -- number of NOPs before entering self-refresh
constant MULTIPLE_ACTIVE_ROWS : boolean := false; -- if true, allow an active row in each bank
constant DATA_WIDTH : natural := 16; -- host & SDRAM data width
constant NROWS : natural := 8192; -- number of rows in SDRAM array
constant NCOLS : natural := 512; -- number of columns in SDRAM array
constant HADDR_WIDTH : natural := 24; -- host-side address width
constant SADDR_WIDTH : natural := 13; -- SDRAM-side address width
 
signal rst_i : std_logic; -- internal reset signal
signal clk_i : std_logic; -- internal master clock signal
signal lock : std_logic; -- SDRAM clock DLL lock indicator
 
-- signals that go through the SDRAM host-side interface
signal opBegun : std_logic; -- SDRAM operation started indicator
signal earlyBegun : std_logic; -- SDRAM operation started indicator
signal ramDone : std_logic; -- SDRAM operation complete indicator
signal rdDone : std_logic; -- SDRAM read operation complete indicator
signal wrDone : std_logic; -- SDRAM write operation complete indicator
signal hAddr : std_logic_vector(HADDR_WIDTH-1 downto 0); -- host address bus
signal hDIn : std_logic_vector(DATA_WIDTH-1 downto 0); -- host-side data to SDRAM
signal hDOut : std_logic_vector(DATA_WIDTH-1 downto 0); -- host-side data from SDRAM
signal hRd : std_logic; -- host-side read control signal
signal hWr : std_logic; -- host-side write control signal
signal rdPending : std_logic; -- read operation pending in SDRAM pipeline
type ram_rd_type is (rd_state0, rd_state1, rd_state2, rd_state3);
type ram_wr_type is (wr_state0, wr_state1, wr_state2, wr_state3, wr_state4);
signal ram_rd_state : ram_rd_type;
signal ram_wr_state : ram_wr_type;
 
-- signal BaudCount : std_logic_vector(5 downto 0);
signal CountL : std_logic_vector(23 downto 0);
signal clk_count : std_logic_vector(0 downto 0);
signal Clk25 : std_logic;
signal pix_clk : 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;
 
 
----------------------------------------
--
-- 4K 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;
 
-----------------------------------------------------------------
--
-- 6850 Compatible ACIA / UART
--
-----------------------------------------------------------------
 
component ACIA_6850
port (
clk : in Std_Logic; -- System Clock
rst : in Std_Logic; -- Reset input (active high)
cs : in Std_Logic; -- miniUART 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 := PIX_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 - 25MHz
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;
 
 
----------------------------------------
--
-- Timer module
--
----------------------------------------
 
component timer
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
);
end component;
 
------------------------------------------------------------
--
-- Bus Trap logic
--
------------------------------------------------------------
 
component trap
port (
clk : in std_logic;
rst : in std_logic;
cs : in std_logic;
rw : in std_logic;
vma : in std_logic;
addr : in std_logic_vector(15 downto 0);
data_in : in std_logic_vector(7 downto 0);
data_out : out std_logic_vector(7 downto 0);
irq : out std_logic
);
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;
 
component XSASDRAMCntl
generic(
FREQ : natural := FREQ; -- operating frequency in KHz
CLK_DIV : real := CLK_DIV; -- divisor for FREQ (can only be 1.0, 1.5, 2.0, 2.5, 3.0, 4.0, 5.0, 8.0 or 16.0)
PIPE_EN : boolean := PIPE_EN; -- if true, enable pipelined read operations
MAX_NOP : natural := MAX_NOP; -- number of NOPs before entering self-refresh
MULTIPLE_ACTIVE_ROWS : boolean := MULTIPLE_ACTIVE_ROWS; -- if true, allow an active row in each bank
DATA_WIDTH : natural := DATA_WIDTH; -- host & SDRAM data width
NROWS : natural := NROWS; -- number of rows in SDRAM array
NCOLS : natural := NCOLS; -- number of columns in SDRAM array
HADDR_WIDTH : natural := HADDR_WIDTH; -- host-side address width
SADDR_WIDTH : natural := SADDR_WIDTH -- SDRAM-side address width
);
port(
-- host side
clk : in std_logic; -- master clock
bufclk : out std_logic; -- buffered master clock
clk1x : out std_logic; -- host clock sync'ed to master clock (and divided if CLK_DIV>1)
clk2x : out std_logic; -- double-speed host clock
lock : out std_logic; -- true when host clock is locked to master clock
rst : in std_logic; -- reset
rd : in std_logic; -- initiate read operation
wr : in std_logic; -- initiate write operation
earlyOpBegun : out std_logic; -- read/write/self-refresh op begun (async)
opBegun : out std_logic; -- read/write/self-refresh op begun (clocked)
rdPending : out std_logic; -- read operation(s) are still in the pipeline
done : out std_logic; -- read or write operation is done
rdDone : out std_logic; -- read done and data is available
hAddr : in std_logic_vector(HADDR_WIDTH-1 downto 0); -- address from host
hDIn : in std_logic_vector(DATA_WIDTH-1 downto 0); -- data from host
hDOut : out std_logic_vector(DATA_WIDTH-1 downto 0); -- data to host
status : out std_logic_vector(3 downto 0); -- diagnostic status of the FSM
 
-- SDRAM side
sclkfb : in std_logic; -- clock from SDRAM after PCB delays
sclk : out std_logic; -- SDRAM clock sync'ed to master clock
cke : out std_logic; -- clock-enable to SDRAM
cs_n : out std_logic; -- chip-select to SDRAM
ras_n : out std_logic; -- SDRAM row address strobe
cas_n : out std_logic; -- SDRAM column address strobe
we_n : out std_logic; -- SDRAM write enable
ba : out std_logic_vector(1 downto 0); -- SDRAM bank address bits
sAddr : out std_logic_vector(SADDR_WIDTH-1 downto 0); -- SDRAM row/column address
sData : inout std_logic_vector(DATA_WIDTH-1 downto 0); -- SDRAM in/out databus
dqmh : out std_logic; -- high databits I/O mask
dqml : out std_logic -- low databits I/O mask
);
end component;
 
--
-- Clock buffer
--
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),
wdata => cpu_data_out,
rdata => rom_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_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 => rxd,
TxD => txd,
DCD_n => dcd_n,
CTS_n => cts_n,
RTS_n => rts_n
);
 
 
my_ACIA_Clock : ACIA_Clock
generic map(
SYS_Clock_Frequency => SYS_Clock_Frequency,
ACIA_Clock_Frequency => ACIA_Clock_Frequency
)
port map(
clk => Clk_i,
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 => ps2_clk,
kbd_data => ps2_dat
);
 
----------------------------------------
--
-- Video Display Unit instantiation
--
----------------------------------------
my_vdu : vdu8
generic map(
VDU_CLOCK_FREQUENCY => CPU_Clock_Frequency, -- HZ
VGA_CLOCK_FREQUENCY => PIX_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 => pix_clk, -- 25 MHz VDU pixel clock
vga_red_o => vga_red_o,
vga_green_o => vga_green_o,
vga_blue_o => vga_blue_o,
vga_hsync_o => vga_hsync_n,
vga_vsync_o => vga_vsync_n
);
 
----------------------------------------
--
-- Timer Module
--
----------------------------------------
my_timer : timer port map (
clk => cpu_clk,
rst => cpu_reset,
cs => timer_cs,
rw => cpu_rw,
addr => cpu_addr(0),
data_in => cpu_data_out,
data_out => timer_data_out,
irq => timer_irq
);
 
----------------------------------------
--
-- Bus Trap Interrupt logic
--
----------------------------------------
my_trap : trap port map (
clk => cpu_clk,
rst => cpu_reset,
cs => trap_cs,
rw => cpu_rw,
vma => cpu_vma,
addr => cpu_addr,
data_in => cpu_data_out,
data_out => trap_data_out,
irq => trap_irq
);
 
 
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)
);
 
------------------------------------------------------------------------
-- Instantiate the SDRAM controller that connects to the memory tester
-- module and interfaces to the external SDRAM chip.
------------------------------------------------------------------------
u1 : xsaSDRAMCntl
generic map(
FREQ => FREQ,
PIPE_EN => PIPE_EN,
DATA_WIDTH => DATA_WIDTH,
MULTIPLE_ACTIVE_ROWS => MULTIPLE_ACTIVE_ROWS,
NROWS => NROWS,
NCOLS => NCOLS,
HADDR_WIDTH => HADDR_WIDTH,
SADDR_WIDTH => SADDR_WIDTH
)
port map(
-- Host Side
clk => CLKA, -- master clock from external clock source (unbuffered)
bufclk => open, -- buffered master clock output
clk1x => clk_i, -- synchronized master clock (accounts for delays to external SDRAM)
clk2x => open, -- synchronized doubled master clock
lock => lock, -- DLL lock indicator
rst => rst_i, -- reset
rd => hRd, -- host-side SDRAM read control from memory tester
wr => hWr, -- host-side SDRAM write control from memory tester
rdPending => rdPending,-- read operation to SDRAM is in progress
opBegun => opBegun, -- indicates memory read/write has begun
earlyOpBegun => earlyBegun, -- early indicator that memory operation has begun
rdDone => rdDone, -- indicates SDRAM memory read operation is done
done => ramDone, -- indicates SDRAM memory read or write operation is done
hAddr => hAddr, -- host-side address from memory tester to SDRAM
hDIn => hDIn, -- test data pattern from memory tester to SDRAM
hDOut => hDOut, -- SDRAM data output to memory tester
status => open, -- SDRAM controller state (for diagnostics)
-- SDRAM Side
sclkfb => SDRAM_clkfb, -- clock feedback with added external PCB delays
sclk => SDRAM_clkout, -- synchronized clock to external SDRAM
cke => SDRAM_cke, -- SDRAM clock enable
cs_n => SDRAM_cs_n, -- SDRAM chip-select
ras_n => SDRAM_ras_n, -- SDRAM RAS
cas_n => SDRAM_cas_n, -- SDRAM CAS
we_n => SDRAM_we_n, -- SDRAM write-enable
ba => SDRAM_ba, -- SDRAM bank address
sAddr => SDRAM_A, -- SDRAM address
sData => SDRAM_D, -- SDRAM databus
dqmh => SDRAM_dqmh, -- SDRAM DQMH
dqml => SDRAM_dqml -- SDRAM DQML
);
 
cpu_clk_buffer : BUFG port map(
i => Clk25,
o => cpu_clk
);
 
pix_clk_buffer : BUFG port map(
i => Clk25,
o => pix_clk
);
----------------------------------------------------------------------
--
-- Process to decode memory map
--
----------------------------------------------------------------------
 
mem_decode: process( cpu_clk,
cpu_addr, cpu_rw, cpu_vma,
dat_addr,
rom_data_out,
flex_data_out,
acia_data_out,
keyboard_data_out,
vdu_data_out,
pb_data_out,
timer_data_out,
trap_data_out,
ram_data_out
)
begin
cpu_data_in <= (others=>'0');
dat_cs <= '0';
rom_cs <= '0';
flex_cs <= '0';
acia_cs <= '0';
keyboard_cs <= '0';
vdu_cs <= '0';
timer_cs <= '0';
trap_cs <= '0';
pb_cs <= '0';
ide_cs <= '0';
ether_cs <= '0';
slot1_cs <= '0';
slot2_cs <= '0';
ram_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
cpu_data_in <= rom_data_out;
rom_cs <= cpu_vma;
 
--
-- IO Devices $E000 - $E7FF
--
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
--
-- Console Port ACIA $E000 - $E00F
--
when "0000" => -- $E000
cpu_data_in <= acia_data_out;
acia_cs <= cpu_vma;
 
--
-- Reserved
-- Floppy Disk Controller port $E010 - $E01F
--
 
--
-- Keyboard port $E020 - $E02F
--
when "0010" => -- $E020
cpu_data_in <= keyboard_data_out;
keyboard_cs <= cpu_vma;
 
--
-- VDU port $E030 - $E03F
--
when "0011" => -- $E030
cpu_data_in <= vdu_data_out;
vdu_cs <= cpu_vma;
 
--
-- Reserved SWTPc MP-T Timer $E040 - $E04F
--
when "0100" => -- $E040
cpu_data_in <= (others=> '0');
 
--
-- Timer $E050 - $E05F
--
when "0101" => -- $E050
cpu_data_in <= timer_data_out;
timer_cs <= cpu_vma;
 
--
-- Bus Trap Logic $E060 - $E06F
--
when "0110" => -- $E060
cpu_data_in <= trap_data_out;
trap_cs <= cpu_vma;
 
--
-- Reserved SWTPc MP-ID PIA Timer/Printer Port $E080 - $E08F
--
 
--
-- Reserved SWTPc MP-ID PTM 6840 Timer Port $E090 - $E09F
--
 
--
-- Remaining 6 slots reserved for non SWTPc Peripherals
--
when others => -- $E0A0 to $E0FF
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;
 
 
--
-- 16-bit Peripheral Bus
-- 6809 Big endian
-- ISA bus little endian
-- Not sure about IDE interface
--
peripheral_bus: process( clk_i, cpu_reset, cpu_rw, cpu_addr, cpu_data_out )
begin
pb_wru <= pb_cs and (not cpu_rw) and (not cpu_addr(0));
pb_wrl <= pb_cs and (not cpu_rw) and cpu_addr(0) ;
pb_rdu <= pb_cs and cpu_rw and (not cpu_addr(0));
pb_rdl <= pb_cs and cpu_rw and cpu_addr(0) ;
pb_a <= cpu_addr(5 downto 1);
 
--
-- Register upper byte from CPU on first CPU write
-- and lower byte from the peripheral bus on first CPU read
--
if cpu_reset = '1' then
pb_wreg <= (others => '0');
pb_rreg <= (others => '0');
elsif clk_i'event and clk_i ='1' then
if pb_wru = '1' then
pb_wreg <= cpu_data_out;
end if;
if pb_rdu = '1' then
pb_rreg <= pb_d(7 downto 0);
end if;
end if;
--
-- Peripheral bus read and write strobes are
-- Syncronized with the 50 MHz clock
-- and are asserted until the peripheral bus hold is released
--
if cpu_reset = '1' then
pb_wr_n <= '1';
pb_rd_n <= '1';
elsif clk_i'event and clk_i ='1' then
if pb_hold = '1' then
pb_wr_n <= not pb_wrl;
pb_rd_n <= not pb_rdu;
else
pb_wr_n <= '1';
pb_rd_n <= '1';
end if;
end if;
--
-- The peripheral bus will be an output
-- the registered even byte on data(15 downto 8)
-- and the CPU odd bytes on data(7 downto 0)
-- on odd byte writes
--
if pb_wrl = '1' then
pb_d <= pb_wreg & cpu_data_out;
else
pb_d <= (others => 'Z');
end if;
 
--
-- On even byte reads,
-- the CPU reads the low (even) byte of the peripheral bus
-- On odd byte reads,
-- the CPU reads the registered (odd byte) input from the peripheral bus
--
if pb_rdu = '1' then
pb_data_out <= pb_d(15 downto 8);
elsif pb_rdl = '1' then
pb_data_out <= pb_rreg;
else
pb_data_out <= (others => '0');
end if;
end process;
 
--
-- Hold Peripheral bus accesses for a few cycles
--
peripheral_bus_hold: process( cpu_clk, cpu_reset, pb_rdu, pb_wrl, ether_rdy )
begin
if cpu_reset = '1' then
pb_release <= '0';
pb_count <= "0000";
pb_hold_state <= hold_release_state;
elsif cpu_clk'event and cpu_clk='1' then
--
-- The perpheral bus hold signal should be generated on
-- 16 bit bus read which will be on even byte reads or
-- 16 bit bus write which will be on odd byte writes.
--
case pb_hold_state is
when hold_release_state =>
pb_release <= '0';
if (pb_rdu = '1') or (pb_wrl = '1') then
pb_count <= "0100";
pb_hold_state <= hold_request_state;
elsif (pb_rdl = '1') or (pb_wru = '1') then
pb_release <= '1';
pb_hold_state <= hold_release_state;
end if;
 
when hold_request_state =>
if pb_count = "0000" then
if ether_rdy = '1' then
pb_release <= '1';
pb_hold_state <= hold_release_state;
end if;
else
pb_count <= pb_count - "0001";
end if;
when others =>
null;
end case;
end if;
end process;
 
--
-- Compact Flash Control
--
compact_flash: process( ide_cs, cpu_addr )
begin
ide_cs0_n <= not( ide_cs ) or cpu_addr(4);
ide_cs1_n <= not( ide_cs and cpu_addr(4));
ide_dmack_n <= '1';
end process;
 
--
-- Interrupts and other bus control signals
--
interrupts : process( lock, rst_n, nmi_n,
pb_cs, pb_hold, pb_release,
ram_cs, ram_hold,
ether_irq,
acia_irq,
keyboard_irq,
trap_irq,
timer_irq
)
begin
cpu_reset <= (not rst_n) or (not lock); -- CPU reset is active high
pb_hold <= pb_cs and (not pb_release);
cpu_irq <= acia_irq or keyboard_irq;
cpu_nmi <= trap_irq or not( nmi_n );
cpu_firq <= timer_irq;
cpu_halt <= '0';
cpu_hold <= pb_hold or ram_hold;
end process;
 
 
--
-- Flash 7 segment LEDS
--
my_led_flasher: process( Clk_i, rst_n, CountL )
begin
if rst_n = '0' then
CountL <= "000000000000000000000000";
elsif(Clk_i'event and Clk_i = '1') then
CountL <= CountL + 1;
end if;
-- S(7 downto 0) <= CountL(23 downto 16);
end process;
 
--
-- Generate a 25 MHz Clock from 50 MHz
--
my_prescaler : process( Clk_i, clk_count )
begin
if Clk_i'event and Clk_i = '1' then
clk_count(0) <= not clk_count(0);
end if;
Clk25 <= clk_count(0);
end process;
 
--
-- Push buttons
--
my_switch_assignments : process( SW2_N, SW3_N, rst_n )
begin
rst_n <= SW2_N;
rst_i <= not rst_n;
nmi_n <= SW3_N;
--
-- Disable Flash memory
--
FLASH_CE_N <= '1';
end process;
 
--
-- RS232 signals:
--
my_acia_assignments : process( RS232_RXD, RS232_CTS, txd, rts_n )
begin
rxd <= RS232_RXD;
cts_n <= RS232_CTS;
dcd_n <= '0';
RS232_TXD <= txd;
RS232_RTS <= rts_n;
end process;
 
--
-- Pin assignments for ethernet controller
--
my_ethernet_assignments : process( clk_i, cpu_reset, ether_cs )
begin
ether_cs_n <= not ether_cs;
ether_aen <= not ether_cs; -- Ethernet address enable not
ether_bhe_n <= '1'; -- Ethernet bus high enable - 8 bit access only
end process;
 
--
-- I/O expansion slot assignments
--
my_slot_assignments : process( slot1_cs, slot2_cs)
begin
slot1_cs_n <= not slot1_cs;
slot2_cs_n <= not slot2_cs;
end process;
 
--
-- VGA ouputs
--
my_vga_assignments : process( vga_red_o, vga_green_o, vga_blue_o )
begin
VGA_red(0) <= vga_red_o;
VGA_red(1) <= vga_red_o;
VGA_red(2) <= vga_red_o;
VGA_green(0) <= vga_green_o;
VGA_green(1) <= vga_green_o;
VGA_green(2) <= vga_green_o;
VGA_blue(0) <= vga_blue_o;
VGA_blue(1) <= vga_blue_o;
VGA_blue(2) <= vga_blue_o;
end process;
 
--
-- SDRAM assignments
--
my_sdram_assignments : process( cpu_clk, clk_i, cpu_reset,
opBegun, rdDone, wrDone,
ram_rd_state, ram_wr_state,
cpu_addr, dat_addr,
cpu_data_out, hDout,
ram_cs, cpu_rw, ram_hold )
begin
if( cpu_reset = '1' ) then
hWr <= '0';
hRd <= '0';
wrDone <= '0';
ram_wr_state <= wr_state0;
ram_rd_state <= rd_state0;
 
elsif( clk_i'event and clk_i='0' ) then
--
-- read state machine
--
case ram_rd_state is
 
when rd_state0 =>
if (ram_hold = '1') and (cpu_rw = '1') then
hRd <= '1';
ram_rd_state <= rd_state1;
end if;
 
when rd_state1 =>
if opBegun = '1' then
ram_rd_state <= rd_state2;
end if;
 
when rd_state2 =>
if rdDone = '1' then
hRd <= '0';
ram_rd_state <= rd_state3;
end if;
 
when rd_state3 =>
if rdDone = '0' then
ram_rd_state <= rd_state0;
end if;
 
when others =>
hRd <= '0';
ram_rd_state <= rd_state0;
end case;
 
--
-- Write state machine
--
case ram_wr_state is
 
when wr_state0 =>
if (ram_hold = '1') and (cpu_rw = '0') then
hWr <= '1';
wrDone <= '0';
ram_wr_state <= wr_state1;
end if;
 
when wr_state1 =>
if opBegun = '1' then
hWr <= '0';
wrDone <= '0';
ram_wr_state <= wr_state2;
end if;
 
when wr_state2 =>
hWr <= '0';
wrDone <= '0';
ram_wr_state <= wr_state3;
 
when wr_state3 =>
hWr <= '0';
wrDone <= '1';
ram_wr_state <= wr_state4;
 
when wr_state4 =>
hWr <= '0';
wrDone <= '0';
ram_wr_state <= wr_state0;
 
when others =>
hWr <= '0';
wrDone <= '0';
ram_wr_state <= wr_state0;
 
end case;
 
end if;
--
-- Strobe host RD and WR signals high on RAM select
-- Return low when cycle has started
--
if( cpu_reset = '1' ) then
ram_hold <= '0';
elsif( cpu_clk'event and cpu_clk='1' ) then
--
-- Hold is intitiated when the RAM is selected
-- and released when access cycle is complete
--
if (ram_hold = '0') and (ram_cs = '1') then
ram_hold <= '1';
elsif (ram_hold = '1') and ((rdDone = '1') or (wrDone = '1')) then
ram_hold <= '0';
end if;
end if;
 
hAddr(23 downto 20) <= "0000";
hAddr(19 downto 12) <= dat_addr;
hAddr(11 downto 0) <= cpu_addr(11 downto 0);
hDin(7 downto 0) <= cpu_data_out;
hDin(15 downto 8) <= (others => '0');
ram_data_out <= hDout(7 downto 0);
 
end process;
 
end rtl; --===================== End of architecture =======================--
 

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