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--===========================================================================--
--
--  S Y N T H E Z I A B L E    I/O Port   C O R E
--
--  www.OpenCores.Org - May 2004
--  This core adheres to the GNU public license  
--
-- File name      : pia6821.vhd
--
-- Purpose        : Implements 2 x 8 bit parallel I/O ports
--                  with programmable data direction registers
--                  
-- Dependencies   : ieee.Std_Logic_1164
--                  ieee.std_logic_unsigned
--
-- Author         : John E. Kent      
--
--===========================================================================----
--
-- Revision History:
--
-- Date:          Revision         Author
-- 1 May 2004     0.0              John Kent
-- Initial version developed from ioport.vhd
--
--===========================================================================----
--
-- Memory Map
--
-- IO + $00 - Port A Data & Direction register
-- IO + $01 - Port A Control register
-- IO + $02 - Port B Data & Direction Direction Register
-- IO + $03 - Port B Control Register
--
 
library ieee;
use ieee.std_logic_1164.all;
use ieee.std_logic_unsigned.all;
 
entity pia6821 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);
         irqa      : out   std_logic;
         irqb      : out   std_logic;
         pa        : inout std_logic_vector(7 downto 0);
         ca1       : in    std_logic;
         ca2       : inout std_logic;
         pb        : inout std_logic_vector(7 downto 0);
         cb1       : in    std_logic;
         cb2       : inout std_logic
         );
end;
 
architecture pia_arch of pia6821 is
 
signal porta_ddr   : std_logic_vector(7 downto 0);
signal porta_data  : std_logic_vector(7 downto 0);
signal porta_ctrl  : std_logic_vector(5 downto 0);
signal porta_read  : std_logic;
 
signal portb_ddr   : std_logic_vector(7 downto 0);
signal portb_data  : std_logic_vector(7 downto 0);
signal portb_ctrl  : std_logic_vector(5 downto 0);
signal portb_read  : std_logic;
signal portb_write : std_logic;
 
signal ca1_del     : std_logic;
signal ca1_rise    : std_logic;
signal ca1_fall    : std_logic;
signal ca1_edge    : std_logic;
signal irqa1       : std_logic;
 
signal ca2_del     : std_logic;
signal ca2_rise    : std_logic;
signal ca2_fall    : std_logic;
signal ca2_edge    : std_logic;
signal irqa2       : std_logic;
signal ca2_out     : std_logic;
 
signal cb1_del     : std_logic;
signal cb1_rise    : std_logic;
signal cb1_fall    : std_logic;
signal cb1_edge    : std_logic;
signal irqb1       : std_logic;
 
signal cb2_del     : std_logic;
signal cb2_rise    : std_logic;
signal cb2_fall    : std_logic;
signal cb2_edge    : std_logic;
signal irqb2       : std_logic;
signal cb2_out     : std_logic;
 
begin
 
--------------------------------
--
-- read I/O port
--
--------------------------------
 
pia_read : process(  addr,      cs,
                     irqa1, irqa2, irqb1, irqb2,
                     porta_ddr,  portb_ddr,
                                                        porta_data, portb_data,
                                                        porta_ctrl, portb_ctrl,
                                                   pa,         pb )
variable count : integer;
begin
      case addr is
             when "00" =>
                    for count in 0 to 7 loop
                           if porta_ctrl(2) = '0' then
                                  data_out(count) <= porta_ddr(count);
                             porta_read <= '0';
            else
                                  if porta_ddr(count) = '1' then
                data_out(count) <= porta_data(count);
              else
                data_out(count) <= pa(count);
              end if;
                             porta_read <= cs;
            end if;
                         end loop;
                         portb_read <= '0';
 
             when "01" =>
                    data_out <= irqa1 & irqa2 & porta_ctrl;
                         porta_read <= '0';
                         portb_read <= '0';
 
                  when "10" =>
                    for count in 0 to 7 loop
                           if portb_ctrl(2) = '0' then
                                  data_out(count) <= portb_ddr(count);
                                  portb_read <= '0';
            else
                                  if portb_ddr(count) = '1' then
                data_out(count) <= portb_data(count);
              else
                data_out(count) <= pb(count);
                                  end if;
                                  portb_read <= cs;
            end if;
                         end loop;
                         porta_read <= '0';
 
                  when "11" =>
                    data_out <= irqb1 & irqb2 & portb_ctrl;
                         porta_read <= '0';
                         portb_read <= '0';
 
                  when others =>
                    data_out <= "00000000";
                         porta_read <= '0';
                         portb_read <= '0';
 
                end case;
end process;
 
---------------------------------
--
-- Write I/O ports
--
---------------------------------
 
pia_write : process( clk, rst, addr, cs, rw, data_in,
                        porta_ctrl, portb_ctrl,
                        porta_data, portb_data,
                                                                porta_ctrl, portb_ctrl,
                                                                porta_ddr, portb_ddr )
begin
  if rst = '1' then
      porta_ddr   <= "00000000";
      porta_data  <= "00000000";
      porta_ctrl  <= "000000";
      portb_ddr   <= "00000000";
      portb_data  <= "00000000";
                portb_ctrl  <= "000000";
                portb_write <= '0';
  elsif clk'event and clk = '1' then
    if cs = '1' and rw = '0' then
      case addr is
             when "00" =>
                    if porta_ctrl(2) = '0' then
                       porta_ddr  <= data_in;
                       porta_data <= porta_data;
                         else
                       porta_ddr  <= porta_ddr;
                       porta_data <= data_in;
                         end if;
                         porta_ctrl  <= porta_ctrl;
                    portb_ddr   <= portb_ddr;
                    portb_data  <= portb_data;
                         portb_ctrl  <= portb_ctrl;
                         portb_write <= '0';
                  when "01" =>
                    porta_ddr   <= porta_ddr;
                    porta_data  <= porta_data;
                         porta_ctrl  <= data_in(5 downto 0);
                    portb_ddr   <= portb_ddr;
                    portb_data  <= portb_data;
                         portb_ctrl  <= portb_ctrl;
                         portb_write <= '0';
             when "10" =>
                    porta_ddr   <= porta_ddr;
                    porta_data  <= porta_data;
                         porta_ctrl  <= porta_ctrl;
                    if portb_ctrl(2) = '0' then
                       portb_ddr   <= data_in;
                       portb_data  <= portb_data;
                            portb_write <= '0';
                         else
                       portb_ddr   <= portb_ddr;
                       portb_data  <= data_in;
                            portb_write <= '1';
                         end if;
                         portb_ctrl  <= portb_ctrl;
                  when "11" =>
                    porta_ddr   <= porta_ddr;
                    porta_data  <= porta_data;
                         porta_ctrl  <= porta_ctrl;
                    portb_ddr   <= portb_ddr;
                    portb_data  <= portb_data;
                         portb_ctrl  <= data_in(5 downto 0);
                         portb_write <= '0';
                  when others =>
                    porta_ddr   <= porta_ddr;
                    porta_data  <= porta_data;
                         porta_ctrl  <= porta_ctrl;
                    portb_ddr   <= portb_ddr;
                    portb_data  <= portb_data;
                         portb_ctrl  <= portb_ctrl;
                         portb_write <= '0';
                end case;
         else
                    porta_ddr   <= porta_ddr;
                    porta_data  <= porta_data;
                         porta_ctrl  <= porta_ctrl;
                    portb_data  <= portb_data;
                    portb_ddr   <= portb_ddr;
                         portb_ctrl  <= portb_ctrl;
                         portb_write <= '0';
         end if;
  end if;
end process;
 
---------------------------------
--
-- direction control port a
--
---------------------------------
porta_direction : process ( porta_data, porta_ddr )
variable count : integer;
begin
  for count in 0 to 7 loop
    if porta_ddr(count) = '1' then
      pa(count) <= porta_data(count);
    else
      pa(count) <= 'Z';
    end if;
  end loop;
end process;
 
---------------------------------
--
-- CA1 Edge detect
--
---------------------------------
ca1_input : process( clk, rst, ca1, ca1_del,
                     ca1_rise, ca1_fall, ca1_edge,
                                                        irqa1, porta_ctrl, porta_read )
begin
  if rst = '1' then
    ca1_del  <= '0';
         ca1_rise <= '0';
    ca1_fall <= '0';
         ca1_edge <= '0';
         irqa1    <= '0';
  elsif clk'event and clk = '0' then
    ca1_del  <= ca1;
    ca1_rise <= (not ca1_del) and ca1;
    ca1_fall <= ca1_del and (not ca1);
         if ca1_edge = '1' then
            irqa1 <= '1';
         elsif porta_read = '1' then
            irqa1 <= '0';
    else
            irqa1 <= irqa1;
    end if;
  end if;
 
  if porta_ctrl(1) = '0' then
         ca1_edge <= ca1_fall;
  else
         ca1_edge <= ca1_rise;
  end if;
end process;
 
---------------------------------
--
-- CA2 Edge detect
--
---------------------------------
ca2_input : process( clk, rst, ca2, ca2_del,
                     ca2_rise, ca2_fall, ca2_edge,
                                                        irqa2, porta_ctrl, porta_read )
begin
  if rst = '1' then
    ca2_del  <= '0';
         ca2_rise <= '0';
    ca2_fall <= '0';
         ca2_edge <= '0';
         irqa2    <= '0';
  elsif clk'event and clk = '0' then
    ca2_del  <= ca2;
    ca2_rise <= (not ca2_del) and ca2;
    ca2_fall <= ca2_del and (not ca2);
         if porta_ctrl(5) = '0' and ca2_edge = '1' then
            irqa2 <= '1';
         elsif porta_read = '1' then
            irqa2 <= '0';
    else
            irqa2 <= irqa2;
    end if;
  end if;
 
  if porta_ctrl(4) = '0' then
         ca2_edge <= ca2_fall;
  else
         ca2_edge <= ca2_rise;
  end if;
end process;
 
---------------------------------
--
-- CA2 output control
--
---------------------------------
ca2_output : process( clk, rst, porta_ctrl, porta_read, ca1_edge, ca2_out )
begin
  if rst='1' then
    ca2_out <= '0';
  elsif clk'event and clk='0' then
    case porta_ctrl(5 downto 3) is
    when "100" => -- read PA clears, CA1 edge sets
      if porta_read = '1' then
             ca2_out <= '0';
      elsif ca1_edge = '1' then
             ca2_out <= '1';
      else
             ca2_out <= ca2_out;
      end if;
    when "101" => -- read PA clears, E sets
      ca2_out <= not porta_read;
    when "110" =>       -- set low
           ca2_out <= '0';
    when "111" =>       -- set high
           ca2_out <= '1';
    when others => -- no change
           ca2_out <= ca2_out;
    end case;
  end if;
end process;
 
---------------------------------
--
-- CA2 direction control
--
---------------------------------
ca2_direction : process( porta_ctrl, ca2, ca2_out )
begin
  if porta_ctrl(5) = '0' then
    ca2 <= 'Z';
  else
    ca2 <= ca2_out;
  end if;
end process;
 
---------------------------------
--
-- direction control port b
--
---------------------------------
portb_direction : process ( portb_data, portb_ddr )
variable count : integer;
begin
  for count in 0 to 7 loop
    if portb_ddr(count) = '1' then
      pb(count) <= portb_data(count);
    else
      pb(count) <= 'Z';
    end if;
  end loop;
end process;
 
---------------------------------
--
-- CB1 Edge detect
--
---------------------------------
cb1_input : process( clk, rst, cb1, cb1_del,
                     cb1_rise, cb1_fall, cb1_edge,
                                                        irqb1, portb_ctrl, portb_read )
begin
  if rst = '1' then
    cb1_del  <= '0';
         cb1_rise <= '0';
    cb1_fall <= '0';
         cb1_edge <= '0';
         irqb1    <= '0';
  elsif clk'event and clk = '0' then
    cb1_del  <= cb1;
    cb1_rise <= (not cb1_del) and cb1;
    cb1_fall <= cb1_del and (not cb1);
         if cb1_edge = '1' then
            irqb1 <= '1';
         elsif portb_read = '1' then
            irqb1 <= '0';
    else
            irqb1 <= irqb1;
    end if;
  end if;
 
  if portb_ctrl(1) = '0' then
         cb1_edge <= cb1_fall;
  else
         cb1_edge <= cb1_rise;
  end if;
end process;
 
---------------------------------
--
-- CB2 Edge detect
--
---------------------------------
cb2_input : process( clk, rst, cb2, cb2_del,
                     cb2_rise, cb2_fall, cb2_edge,
                                                        irqb2, portb_ctrl, portb_read )
begin
  if rst = '1' then
    cb2_del  <= '0';
         cb2_rise <= '0';
    cb2_fall <= '0';
         cb2_edge <= '0';
         irqb2    <= '0';
  elsif clk'event and clk = '0' then
    cb2_del  <= cb2;
    cb2_rise <= (not cb2_del) and cb2;
    cb2_fall <= cb2_del and (not cb2);
         if portb_ctrl(5) = '0' and cb2_edge = '1' then
            irqb2 <= '1';
         elsif portb_read = '1' then
            irqb2 <= '0';
    else
            irqb2 <= irqb2;
    end if;
  end if;
 
  if portb_ctrl(4) = '0' then
         cb2_edge <= cb2_fall;
  else
         cb2_edge <= cb2_rise;
  end if;
 
end process;
 
---------------------------------
--
-- CB2 output control
--
---------------------------------
cb2_output : process( clk, rst, portb_ctrl, portb_write, cb1_edge, cb2_out )
begin
  if rst='1' then
    cb2_out <= '0';
  elsif clk'event and clk='0' then
    case portb_ctrl(5 downto 3) is
    when "100" => -- write PB clears, CA1 edge sets
      if portb_write = '1' then
             cb2_out <= '0';
      elsif cb1_edge = '1' then
             cb2_out <= '1';
      else
             cb2_out <= cb2_out;
      end if;
    when "101" => -- write PB clears, E sets
      cb2_out <= not portb_write;
    when "110" =>       -- set low
           cb2_out <= '0';
    when "111" =>       -- set high
           cb2_out <= '1';
    when others => -- no change
           cb2_out <= cb2_out;
    end case;
  end if;
end process;
 
---------------------------------
--
-- CB2 direction control
--
---------------------------------
cb2_direction : process( portb_ctrl, cb2, cb2_out )
begin
  if portb_ctrl(5) = '0' then
    cb2 <= 'Z';
  else
    cb2 <= cb2_out;
  end if;
end process;
 
---------------------------------
--
-- IRQ control
--
---------------------------------
pia_irq : process( irqa1, irqa2, irqb1, irqb2, porta_ctrl, portb_ctrl )
begin
  irqa <= (irqa1 and porta_ctrl(0)) or (irqa2 and porta_ctrl(3));
  irqb <= (irqb1 and portb_ctrl(0)) or (irqb2 and portb_ctrl(3));
end process;
 
end pia_arch;
 

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[/] [System09/] [branches/] [mkfiles_rev1/] [rtl/] [VHDL/] [pia6821.vhd] - Blame information for rev 104

Line No.	Rev	Author	Line
1	19	dilbert57	`--===========================================================================--`
2			`--`
3			`-- S Y N T H E Z I A B L E I/O Port C O R E`
4			`--`
5			`-- www.OpenCores.Org - May 2004`
6			`-- This core adheres to the GNU public license`
7			`--`
8			`-- File name : pia6821.vhd`
9			`--`
10			`-- Purpose : Implements 2 x 8 bit parallel I/O ports`
11			`-- with programmable data direction registers`
12			`--`
13			`-- Dependencies : ieee.Std_Logic_1164`
14			`-- ieee.std_logic_unsigned`
15			`--`
16			`-- Author : John E. Kent`
17			`--`
18			`--===========================================================================----`
19			`--`
20			`-- Revision History:`
21			`--`
22			`-- Date: Revision Author`
23			`-- 1 May 2004 0.0 John Kent`
24			`-- Initial version developed from ioport.vhd`
25			`--`
26			`--===========================================================================----`
27			`--`
28			`-- Memory Map`
29			`--`
30			`-- IO + $00 - Port A Data & Direction register`
31			`-- IO + $01 - Port A Control register`
32			`-- IO + $02 - Port B Data & Direction Direction Register`
33			`-- IO + $03 - Port B Control Register`
34			`--`
35
36			`library ieee;`
37			`use ieee.std_logic_1164.all;`
38			`use ieee.std_logic_unsigned.all;`
39
40			`entity pia6821 is`
41			`port (`
42			`clk : in std_logic;`
43			`rst : in std_logic;`
44			`cs : in std_logic;`
45			`rw : in std_logic;`
46			`addr : in std_logic_vector(1 downto 0);`
47			`data_in : in std_logic_vector(7 downto 0);`
48			`data_out : out std_logic_vector(7 downto 0);`
49			`irqa : out std_logic;`
50			`irqb : out std_logic;`
51			`pa : inout std_logic_vector(7 downto 0);`
52			`ca1 : in std_logic;`
53			`ca2 : inout std_logic;`
54			`pb : inout std_logic_vector(7 downto 0);`
55			`cb1 : in std_logic;`
56			`cb2 : inout std_logic`
57			`);`
58			`end;`
59
60			`architecture pia_arch of pia6821 is`
61
62			`signal porta_ddr : std_logic_vector(7 downto 0);`
63			`signal porta_data : std_logic_vector(7 downto 0);`
64			`signal porta_ctrl : std_logic_vector(5 downto 0);`
65			`signal porta_read : std_logic;`
66
67			`signal portb_ddr : std_logic_vector(7 downto 0);`
68			`signal portb_data : std_logic_vector(7 downto 0);`
69			`signal portb_ctrl : std_logic_vector(5 downto 0);`
70			`signal portb_read : std_logic;`
71			`signal portb_write : std_logic;`
72
73			`signal ca1_del : std_logic;`
74			`signal ca1_rise : std_logic;`
75			`signal ca1_fall : std_logic;`
76			`signal ca1_edge : std_logic;`
77			`signal irqa1 : std_logic;`
78
79			`signal ca2_del : std_logic;`
80			`signal ca2_rise : std_logic;`
81			`signal ca2_fall : std_logic;`
82			`signal ca2_edge : std_logic;`
83			`signal irqa2 : std_logic;`
84			`signal ca2_out : std_logic;`
85
86			`signal cb1_del : std_logic;`
87			`signal cb1_rise : std_logic;`
88			`signal cb1_fall : std_logic;`
89			`signal cb1_edge : std_logic;`
90			`signal irqb1 : std_logic;`
91
92			`signal cb2_del : std_logic;`
93			`signal cb2_rise : std_logic;`
94			`signal cb2_fall : std_logic;`
95			`signal cb2_edge : std_logic;`
96			`signal irqb2 : std_logic;`
97			`signal cb2_out : std_logic;`
98
99			`begin`
100
101			`--------------------------------`
102			`--`
103			`-- read I/O port`
104			`--`
105			`--------------------------------`
106
107			`pia_read : process( addr, cs,`
108			`irqa1, irqa2, irqb1, irqb2,`
109			`porta_ddr, portb_ddr,`
110			`porta_data, portb_data,`
111			`porta_ctrl, portb_ctrl,`
112			`pa, pb )`
113			`variable count : integer;`
114			`begin`
115			`case addr is`
116			`when "00" =>`
117			`for count in 0 to 7 loop`
118			`if porta_ctrl(2) = '0' then`
119			`data_out(count) <= porta_ddr(count);`
120			`porta_read <= '0';`
121			`else`
122			`if porta_ddr(count) = '1' then`
123			`data_out(count) <= porta_data(count);`
124			`else`
125			`data_out(count) <= pa(count);`
126			`end if;`
127			`porta_read <= cs;`
128			`end if;`
129			`end loop;`
130			`portb_read <= '0';`
131
132			`when "01" =>`
133			`data_out <= irqa1 & irqa2 & porta_ctrl;`
134			`porta_read <= '0';`
135			`portb_read <= '0';`
136
137			`when "10" =>`
138			`for count in 0 to 7 loop`
139			`if portb_ctrl(2) = '0' then`
140			`data_out(count) <= portb_ddr(count);`
141			`portb_read <= '0';`
142			`else`
143			`if portb_ddr(count) = '1' then`
144			`data_out(count) <= portb_data(count);`
145			`else`
146			`data_out(count) <= pb(count);`
147			`end if;`
148			`portb_read <= cs;`
149			`end if;`
150			`end loop;`
151			`porta_read <= '0';`
152
153			`when "11" =>`
154			`data_out <= irqb1 & irqb2 & portb_ctrl;`
155			`porta_read <= '0';`
156			`portb_read <= '0';`
157
158			`when others =>`
159			`data_out <= "00000000";`
160			`porta_read <= '0';`
161			`portb_read <= '0';`
162
163			`end case;`
164			`end process;`
165
166			`---------------------------------`
167			`--`
168			`-- Write I/O ports`
169			`--`
170			`---------------------------------`
171
172			`pia_write : process( clk, rst, addr, cs, rw, data_in,`
173			`porta_ctrl, portb_ctrl,`
174			`porta_data, portb_data,`
175			`porta_ctrl, portb_ctrl,`
176			`porta_ddr, portb_ddr )`
177			`begin`
178			`if rst = '1' then`
179			`porta_ddr <= "00000000";`
180			`porta_data <= "00000000";`
181			`porta_ctrl <= "000000";`
182			`portb_ddr <= "00000000";`
183			`portb_data <= "00000000";`
184			`portb_ctrl <= "000000";`
185			`portb_write <= '0';`
186			`elsif clk'event and clk = '1' then`
187			`if cs = '1' and rw = '0' then`
188			`case addr is`
189			`when "00" =>`
190			`if porta_ctrl(2) = '0' then`
191			`porta_ddr <= data_in;`
192			`porta_data <= porta_data;`
193			`else`
194			`porta_ddr <= porta_ddr;`
195			`porta_data <= data_in;`
196			`end if;`
197			`porta_ctrl <= porta_ctrl;`
198			`portb_ddr <= portb_ddr;`
199			`portb_data <= portb_data;`
200			`portb_ctrl <= portb_ctrl;`
201			`portb_write <= '0';`
202			`when "01" =>`
203			`porta_ddr <= porta_ddr;`
204			`porta_data <= porta_data;`
205			`porta_ctrl <= data_in(5 downto 0);`
206			`portb_ddr <= portb_ddr;`
207			`portb_data <= portb_data;`
208			`portb_ctrl <= portb_ctrl;`
209			`portb_write <= '0';`
210			`when "10" =>`
211			`porta_ddr <= porta_ddr;`
212			`porta_data <= porta_data;`
213			`porta_ctrl <= porta_ctrl;`
214			`if portb_ctrl(2) = '0' then`
215			`portb_ddr <= data_in;`
216			`portb_data <= portb_data;`
217			`portb_write <= '0';`
218			`else`
219			`portb_ddr <= portb_ddr;`
220			`portb_data <= data_in;`
221			`portb_write <= '1';`
222			`end if;`
223			`portb_ctrl <= portb_ctrl;`
224			`when "11" =>`
225			`porta_ddr <= porta_ddr;`
226			`porta_data <= porta_data;`
227			`porta_ctrl <= porta_ctrl;`
228			`portb_ddr <= portb_ddr;`
229			`portb_data <= portb_data;`
230			`portb_ctrl <= data_in(5 downto 0);`
231			`portb_write <= '0';`
232			`when others =>`
233			`porta_ddr <= porta_ddr;`
234			`porta_data <= porta_data;`
235			`porta_ctrl <= porta_ctrl;`
236			`portb_ddr <= portb_ddr;`
237			`portb_data <= portb_data;`
238			`portb_ctrl <= portb_ctrl;`
239			`portb_write <= '0';`
240			`end case;`
241			`else`
242			`porta_ddr <= porta_ddr;`
243			`porta_data <= porta_data;`
244			`porta_ctrl <= porta_ctrl;`
245			`portb_data <= portb_data;`
246			`portb_ddr <= portb_ddr;`
247			`portb_ctrl <= portb_ctrl;`
248			`portb_write <= '0';`
249			`end if;`
250			`end if;`
251			`end process;`
252
253			`---------------------------------`
254			`--`
255			`-- direction control port a`
256			`--`
257			`---------------------------------`
258			`porta_direction : process ( porta_data, porta_ddr )`
259			`variable count : integer;`
260			`begin`
261			`for count in 0 to 7 loop`
262			`if porta_ddr(count) = '1' then`
263			`pa(count) <= porta_data(count);`
264			`else`
265			`pa(count) <= 'Z';`
266			`end if;`
267			`end loop;`
268			`end process;`
269
270			`---------------------------------`
271			`--`
272			`-- CA1 Edge detect`
273			`--`
274			`---------------------------------`
275			`ca1_input : process( clk, rst, ca1, ca1_del,`
276			`ca1_rise, ca1_fall, ca1_edge,`
277			`irqa1, porta_ctrl, porta_read )`
278			`begin`
279			`if rst = '1' then`
280			`ca1_del <= '0';`
281			`ca1_rise <= '0';`
282			`ca1_fall <= '0';`
283			`ca1_edge <= '0';`
284			`irqa1 <= '0';`
285			`elsif clk'event and clk = '0' then`
286			`ca1_del <= ca1;`
287			`ca1_rise <= (not ca1_del) and ca1;`
288			`ca1_fall <= ca1_del and (not ca1);`
289			`if ca1_edge = '1' then`
290			`irqa1 <= '1';`
291			`elsif porta_read = '1' then`
292			`irqa1 <= '0';`
293			`else`
294			`irqa1 <= irqa1;`
295			`end if;`
296			`end if;`
297
298			`if porta_ctrl(1) = '0' then`
299			`ca1_edge <= ca1_fall;`
300			`else`
301			`ca1_edge <= ca1_rise;`
302			`end if;`
303			`end process;`
304
305			`---------------------------------`
306			`--`
307			`-- CA2 Edge detect`
308			`--`
309			`---------------------------------`
310			`ca2_input : process( clk, rst, ca2, ca2_del,`
311			`ca2_rise, ca2_fall, ca2_edge,`
312			`irqa2, porta_ctrl, porta_read )`
313			`begin`
314			`if rst = '1' then`
315			`ca2_del <= '0';`
316			`ca2_rise <= '0';`
317			`ca2_fall <= '0';`
318			`ca2_edge <= '0';`
319			`irqa2 <= '0';`
320			`elsif clk'event and clk = '0' then`
321			`ca2_del <= ca2;`
322			`ca2_rise <= (not ca2_del) and ca2;`
323			`ca2_fall <= ca2_del and (not ca2);`
324			`if porta_ctrl(5) = '0' and ca2_edge = '1' then`
325			`irqa2 <= '1';`
326			`elsif porta_read = '1' then`
327			`irqa2 <= '0';`
328			`else`
329			`irqa2 <= irqa2;`
330			`end if;`
331			`end if;`
332
333			`if porta_ctrl(4) = '0' then`
334			`ca2_edge <= ca2_fall;`
335			`else`
336			`ca2_edge <= ca2_rise;`
337			`end if;`
338			`end process;`
339
340			`---------------------------------`
341			`--`
342			`-- CA2 output control`
343			`--`
344			`---------------------------------`
345			`ca2_output : process( clk, rst, porta_ctrl, porta_read, ca1_edge, ca2_out )`
346			`begin`
347			`if rst='1' then`
348			`ca2_out <= '0';`
349			`elsif clk'event and clk='0' then`
350			`case porta_ctrl(5 downto 3) is`
351			`when "100" => -- read PA clears, CA1 edge sets`
352			`if porta_read = '1' then`
353			`ca2_out <= '0';`
354			`elsif ca1_edge = '1' then`
355			`ca2_out <= '1';`
356			`else`
357			`ca2_out <= ca2_out;`
358			`end if;`
359			`when "101" => -- read PA clears, E sets`
360			`ca2_out <= not porta_read;`
361			`when "110" => -- set low`
362			`ca2_out <= '0';`
363			`when "111" => -- set high`
364			`ca2_out <= '1';`
365			`when others => -- no change`
366			`ca2_out <= ca2_out;`
367			`end case;`
368			`end if;`
369			`end process;`
370
371			`---------------------------------`
372			`--`
373			`-- CA2 direction control`
374			`--`
375			`---------------------------------`
376			`ca2_direction : process( porta_ctrl, ca2, ca2_out )`
377			`begin`
378			`if porta_ctrl(5) = '0' then`
379			`ca2 <= 'Z';`
380			`else`
381			`ca2 <= ca2_out;`
382			`end if;`
383			`end process;`
384
385			`---------------------------------`
386			`--`
387			`-- direction control port b`
388			`--`
389			`---------------------------------`
390			`portb_direction : process ( portb_data, portb_ddr )`
391			`variable count : integer;`
392			`begin`
393			`for count in 0 to 7 loop`
394			`if portb_ddr(count) = '1' then`
395			`pb(count) <= portb_data(count);`
396			`else`
397			`pb(count) <= 'Z';`
398			`end if;`
399			`end loop;`
400			`end process;`
401
402			`---------------------------------`
403			`--`
404			`-- CB1 Edge detect`
405			`--`
406			`---------------------------------`
407			`cb1_input : process( clk, rst, cb1, cb1_del,`
408			`cb1_rise, cb1_fall, cb1_edge,`
409			`irqb1, portb_ctrl, portb_read )`
410			`begin`
411			`if rst = '1' then`
412			`cb1_del <= '0';`
413			`cb1_rise <= '0';`
414			`cb1_fall <= '0';`
415			`cb1_edge <= '0';`
416			`irqb1 <= '0';`
417			`elsif clk'event and clk = '0' then`
418			`cb1_del <= cb1;`
419			`cb1_rise <= (not cb1_del) and cb1;`
420			`cb1_fall <= cb1_del and (not cb1);`
421			`if cb1_edge = '1' then`
422			`irqb1 <= '1';`
423			`elsif portb_read = '1' then`
424			`irqb1 <= '0';`
425			`else`
426			`irqb1 <= irqb1;`
427			`end if;`
428			`end if;`
429
430			`if portb_ctrl(1) = '0' then`
431			`cb1_edge <= cb1_fall;`
432			`else`
433			`cb1_edge <= cb1_rise;`
434			`end if;`
435			`end process;`
436
437			`---------------------------------`
438			`--`
439			`-- CB2 Edge detect`
440			`--`
441			`---------------------------------`
442			`cb2_input : process( clk, rst, cb2, cb2_del,`
443			`cb2_rise, cb2_fall, cb2_edge,`
444			`irqb2, portb_ctrl, portb_read )`
445			`begin`
446			`if rst = '1' then`
447			`cb2_del <= '0';`
448			`cb2_rise <= '0';`
449			`cb2_fall <= '0';`
450			`cb2_edge <= '0';`
451			`irqb2 <= '0';`
452			`elsif clk'event and clk = '0' then`
453			`cb2_del <= cb2;`
454			`cb2_rise <= (not cb2_del) and cb2;`
455			`cb2_fall <= cb2_del and (not cb2);`
456			`if portb_ctrl(5) = '0' and cb2_edge = '1' then`
457			`irqb2 <= '1';`
458			`elsif portb_read = '1' then`
459			`irqb2 <= '0';`
460			`else`
461			`irqb2 <= irqb2;`
462			`end if;`
463			`end if;`
464
465			`if portb_ctrl(4) = '0' then`
466			`cb2_edge <= cb2_fall;`
467			`else`
468			`cb2_edge <= cb2_rise;`
469			`end if;`
470
471			`end process;`
472
473			`---------------------------------`
474			`--`
475			`-- CB2 output control`
476			`--`
477			`---------------------------------`
478			`cb2_output : process( clk, rst, portb_ctrl, portb_write, cb1_edge, cb2_out )`
479			`begin`
480			`if rst='1' then`
481			`cb2_out <= '0';`
482			`elsif clk'event and clk='0' then`
483			`case portb_ctrl(5 downto 3) is`
484			`when "100" => -- write PB clears, CA1 edge sets`
485			`if portb_write = '1' then`
486			`cb2_out <= '0';`
487			`elsif cb1_edge = '1' then`
488			`cb2_out <= '1';`
489			`else`
490			`cb2_out <= cb2_out;`
491			`end if;`
492			`when "101" => -- write PB clears, E sets`
493			`cb2_out <= not portb_write;`
494			`when "110" => -- set low`
495			`cb2_out <= '0';`
496			`when "111" => -- set high`
497			`cb2_out <= '1';`
498			`when others => -- no change`
499			`cb2_out <= cb2_out;`
500			`end case;`
501			`end if;`
502			`end process;`
503
504			`---------------------------------`
505			`--`
506			`-- CB2 direction control`
507			`--`
508			`---------------------------------`
509			`cb2_direction : process( portb_ctrl, cb2, cb2_out )`
510			`begin`
511			`if portb_ctrl(5) = '0' then`
512			`cb2 <= 'Z';`
513			`else`
514			`cb2 <= cb2_out;`
515			`end if;`
516			`end process;`
517
518			`---------------------------------`
519			`--`
520			`-- IRQ control`
521			`--`
522			`---------------------------------`
523			`pia_irq : process( irqa1, irqa2, irqb1, irqb2, porta_ctrl, portb_ctrl )`
524			`begin`
525			`irqa <= (irqa1 and porta_ctrl(0)) or (irqa2 and porta_ctrl(3));`
526			`irqb <= (irqb1 and portb_ctrl(0)) or (irqb2 and portb_ctrl(3));`
527			`end process;`
528
529			`end pia_arch;`
530