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Rev 150 → Rev 149

/rtl/System09_Digilent_Atlys/System09_Atlys.vhd
0,0 → 1,977
--===========================================================================----
--
-- 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 (acia6850.vhd) ACIA / UART
-- 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 system09 is
port(
CLKA : in Std_Logic; -- 100MHz Clock input
-- CLKB : in Std_Logic; -- 50MHz Clock input
SW2_N : in Std_logic; -- Master Reset input (active low)
SW3_N : in Std_logic; -- Non Maskable Interrupt input (active low)
 
 
 
-- RS232 Port
RS232_RXD : in Std_Logic;
RS232_TXD : out Std_Logic;
 
 
-- Status 7 segment LED
S : out std_logic_vector(7 downto 0)
 
 
-- CPU Debug Interface signals
-- cpu_reset_o : out Std_Logic;
-- cpu_clk_o : out Std_Logic;
-- cpu_rw_o : out std_logic;
-- cpu_vma_o : out std_logic;
-- cpu_halt_o : out std_logic;
-- cpu_hold_o : out std_logic;
-- cpu_firq_o : out std_logic;
-- cpu_irq_o : out std_logic;
-- cpu_nmi_o : out std_logic;
-- cpu_addr_o : out std_logic_vector(15 downto 0);
-- cpu_data_in_o : out std_logic_vector(7 downto 0);
-- cpu_data_out_o : out std_logic_vector(7 downto 0);
);
end system09;
 
-------------------------------------------------------------------------------
-- Architecture for System09
-------------------------------------------------------------------------------
architecture rtl of system09 is
 
-----------------------------------------------------------------------------
-- 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)
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
 
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_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 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 );
 
-----------------------------------------------------------------------------
-- Signals
-----------------------------------------------------------------------------
-- 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_rd_req : std_logic; -- ram read request (asynch set on ram read, cleared falling CPU clock edge)
signal ram_wr_req : std_logic; -- ram write request (set on rising CPU clock edge, asynch clear on acknowledge)
signal ram_hold : std_logic; -- hold off slow accesses
signal ram_release : std_logic; -- Release ram hold
 
-- 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
 
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 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,
ram_state_3 );
signal ram_state : ram_type;
 
signal flash_ce_n : std_logic;
signal rs232_cts : Std_Logic;
signal rs232_rts : Std_Logic;
signal ether_cs_n : std_logic;
signal ether_aen : std_logic;
signal ether_bhe_n : std_logic;
signal slot1_cs_n : std_logic;
signal slot2_cs_n : std_logic;
-- 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;
signal Clk25 : std_logic;
 
signal vga_clk : std_logic;
-----------------------------------------------------------------
--
-- CPU09 CPU core
--
-----------------------------------------------------------------
 
component cpu09
port (
clk: in std_logic;
rst: in std_logic;
vma: out std_logic;
addr: out std_logic_vector(15 downto 0);
rw: out std_logic; -- Asynchronous memory interface
data_out: out std_logic_vector(7 downto 0);
data_in: in std_logic_vector(7 downto 0);
irq: in std_logic;
firq: in std_logic;
nmi: in std_logic;
halt: in std_logic;
hold: in std_logic
);
end component;
 
----------------------------------------
--
-- 4K Block RAM Monitor ROM
-- $F000 - $FFFF
--
----------------------------------------
 
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);
data_out : out std_logic_vector (7 downto 0);
data_in : 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);
data_out : out std_logic_vector (7 downto 0);
data_in : in std_logic_vector (7 downto 0)
);
end component;
 
-----------------------------------------------------------------
--
-- 6850 Compatible ACIA / UART
--
-----------------------------------------------------------------
 
component acia6850
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
addr : in Std_Logic; -- Register Select
data_in : in Std_Logic_Vector(7 downto 0); -- Data Bus In
data_out : out Std_Logic_Vector(7 downto 0); -- Data Bus Out
irq : out Std_Logic; -- Interrupt
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_CLK_FREQ : integer := SYS_CLK_FREQ;
ACIA_CLK_FREQ : integer := ACIA_CLK_FREQ
);
port (
clk : in Std_Logic; -- System Clock Input
ACIA_clk : out Std_logic -- ACIA Clock output
);
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;
 
 
--
-- 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,
vma => cpu_vma,
addr => cpu_addr(15 downto 0),
rw => cpu_rw,
data_out => cpu_data_out,
data_in => cpu_data_in,
irq => cpu_irq,
firq => cpu_firq,
nmi => cpu_nmi,
halt => cpu_halt,
hold => cpu_hold
);
 
my_rom : mon_rom
port map (
clk => cpu_clk,
rst => cpu_reset,
cs => rom_cs,
rw => '1',
addr => cpu_addr(11 downto 0),
data_in => cpu_data_out,
data_out => 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),
data_out => flex_data_out,
data_in => cpu_data_out
);
 
my_acia : acia6850
port map (
clk => cpu_clk,
rst => cpu_reset,
cs => acia_cs,
rw => cpu_rw,
addr => cpu_addr(0),
data_in => cpu_data_out,
data_out => acia_data_out,
irq => acia_irq,
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_CLK_FREQ => SYS_CLK_FREQ,
ACIA_CLK_FREQ => ACIA_CLK_FREQ
)
port map(
clk => Clk_i,
acia_clk => acia_clk
);
 
----------------------------------------
--
-- 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)
);
 
 
cpu_clk_buffer : BUFG
port map(
i => Clk25,
o => cpu_clk
);
 
----------------------------------------------------------------------
--
-- Process to decode memory map
--
----------------------------------------------------------------------
 
mem_decode: process( 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 -- $FFxx
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;
 
 
 
--
-- Interrupts and other bus control signals
--
interrupts : process( SW3_N,
pb_cs, pb_hold, pb_release, ram_hold,
-- ether_irq,
acia_irq,
keyboard_irq,
trap_irq,
timer_irq
)
begin
pb_hold <= pb_cs and (not pb_release);
cpu_irq <= acia_irq or keyboard_irq;
cpu_nmi <= trap_irq or not( SW3_N );
cpu_firq <= timer_irq;
cpu_halt <= '0';
cpu_hold <= pb_hold or ram_hold;
FLASH_CE_N <= '1';
end process;
 
--
-- Flash 7 segment LEDS
--
my_led_flasher: process( clk_i, rst_i, CountL )
begin
if rst_i = '1' then
CountL <= "000000000000000000000000";
elsif rising_edge(clk_i) then
CountL <= CountL + 1;
end if;
-- S(7 downto 0) <= CountL(23 downto 16);
end process;
 
--
-- Generate CPU & Pixel Clock from Memory Clock
--
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
clk25 <= '0';
elsif clk_count = (CPU_CLK_DIV/2) then
clk25 <= '1';
end if;
end if;
end process;
 
--
-- Reset button and reset timer
--
my_switch_assignments : process( rst_i, SW2_N, lock )
begin
rst_i <= not SW2_N;
cpu_reset <= rst_i or (not lock);
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;
 
 
--
-- 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
ram_rd_req <= '0';
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;
end if;
end process;
 
--
-- CPU write data to RAM valid on rising CPU clock edge
--
ram_write_request: process( hWr, cpu_clk, ram_cs, cpu_rw, ram_release )
begin
if hWr = '1' then
ram_wr_req <= '0';
elsif rising_edge(cpu_clk) then
if (ram_cs = '1') and (cpu_rw = '0') and (ram_release = '1') then
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;
 
end rtl; --===================== End of architecture =======================--
 

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