3,             // Number of bits in the fields counter
               2              // Number of bits in the digits counter
               )
  syscon_1 (                  // instance name
  .clk_i(clk_s0),
  .reset_i(reset),
  .master_bg_i(master_br),
  .ack_i(code_space || rgb_space || ram_space || io_space),
  .err_i(1'b0),
  .master_adr_i(risc_aux_adr),
  .master_stb_i(risc_stb),
  .master_we_i(risc_aux_we),
  .rs232_rxd_i(rs232_rxd),
  .dat_io(dat),
  .rst_o(rst),
  .master_br_o(master_br),
  .stb_o(stb),
  .cyc_o(),
  .adr_o(adr),
  .we_o(we),
  .rs232_txd_o(rs232_txd)
  );

// RAM decodes

// In this project, the address bus (adr) is 16 bits wide.  This provides
// enough address range to address the entire program space of the processor
// plus the entire screen memory of the LCD panel at 128 by 92 resolution.
// (There are only 12288 pixels!)
//
// The processor is able to access this address space indirectly, by setting
// up the address first within its aux_adr_lo and aux_adr_hi registers, then
// issuing reads/writes to the aux_dat location.
//
// In this way, the processor is able to load data into its own code space,
// by way of the dual port RAM...  Of course, the user must be careful not
// to currupt the code which is running on the processor during this process!

//   AUX Addr.   Width   Purpose
//----------------------------------------------------------
//  0000 - 01ff  8-bit   processor code space block 0.
//  0200 - 03ff  8-bit   processor code space block 1.
//  0400 - 05ff  8-bit   processor code space block 2.
//  0600 - 07ff  8-bit   processor code space block 3.
//  4000 - 4fff  3-bit   display panel pixels block 0 (4096 pixels).
//  5000 - 5fff  3-bit   display panel pixels block 1 (4096 pixels).
//  6000 - 6fff  3-bit   display panel pixels block 2 (4096 pixels).
//  ff00 - ffff  8-bit   peripheral I/O register space

assign code_space = ((adr[15:14] == 0) && stb);         // 1st 16k
assign rgb_space  = ((adr[15:14] == 1) && stb);         // 2nd 16k
assign ram_space  = ((adr[15:9] == 7'b1000000) && stb); // 512 bytes at 8000h
assign io_space   = ((adr[15:8]  == 8'hff) && stb); // last 256 bytes
assign io_sel   = (io_space)?(1 << adr[4:3]):0;

assign r0_wire = {~ps2_clk,~ps2_data};
assign r1_wire = {clk_s1,switch};

reg_8_pack #(
             8,               // Size of r0
             5,               // Size of r1
             8,               // Size of r2
             5,               // Size of r3
             8,               // Size of r4
             6,               // Size of r5
             2,               // Size of r6
             8,               // Size of r7
             2,               // Read only regs.
             8                // Size of the data bus.
             )
  reg_8_pack_1                // Instance name
  (
   .clk_i(clk_s0),
   .rst_i(reset),
   .sel_i(io_sel[0]),
   .we_i(we),
   .adr_i(adr[2:0]),  // byte addressed...
   .dat_io(dat),
   .r0(r0_wire),
   .r1(r1_wire),
   .r2(break_prog_adr[7:0]),
   .r3(break_prog_adr[12:8]),
   .r4(break_prog_dat[7:0]),
   .r5(break_prog_dat[13:8]),
   .r6(break_enable),
   .r7(led)
   );


// The following register set and logic is to control single stepping the
// processor.  Actually, stepping in groups of 2, 3, 4 or more is permitted.
// Also, a breakpoint will reset the stepping counter.
// If running free, a breakpoint will reset the "run_free" and "forced_reset"
// bits.
reg_4_pack_clrset #(
             1,               // Size of r0
             1,               // Size of r1
             6,               // Size of r2
             2,               // Size of r3
             0,               // Read only regs.
             8                // Size of the data bus.
             )
  reg_4_pack_clrset_1         // Instance name
  (
   .clk_i(clk_s0),
   .rst_i(reset),
   .sel_i(io_sel[1]),
   .we_i(we),
   .adr_i(adr[1:0]),  // byte addressed... byte accessible only
   .clr_i({2'b0,begin_stepping,breakpoint}),
   .set_i(4'b0),
   .dat_io(dat[7:0]),
   .r0(),
   .r1(begin_stepping),
   .r2(clocks_to_step),
   .r3(processor_control)
   );

assign run_free = processor_control[1];  // Not free running at power up
assign forced_reset = processor_control[0];

// This part generates the bus_rdy signal for the processor.
// This is how single stepping is implemented.  Actually, execution in
// steps of 2,3 or more instructions at a time is also allowed.
assign reset_single_stepper = reset || breakpoint;
always @(posedge clk_s0 or posedge reset_single_stepper)
begin
  if (reset_single_stepper) step_count <= 0;  // Asynchronous reset
  else
  begin // Clock edge
    if (begin_stepping) step_count <= clocks_to_step;
    else if (stepping_active) step_count <= step_count - 1;
  end
end
assign stepping_active = (step_count > 0);
assign bus_rdy = (stepping_active || run_free) && (~breakpoint);
assign breakpoint = (
             (break_enable[0] && (break_prog_adr == risc_prog_adr))
          || (break_enable[1] && (break_prog_dat == risc_prog_dat[13:0]))
                     );

//---------------------------------------------------------------------
// 2048 bytes of program RAM (2048 x 8 on A, 1024 x 16 on B)
assign dat = (code_space && ~we)?code_ram_dat_o:{8{1'bZ}};

ramb16_s8_s16
  code_space_ram
  (
   .dat_o_s8a(code_ram_dat_o),
   .dat_i_s8a(dat),
   .adr_i_s8a(adr[10:0]),
   .clk_i_s8a(sys_clk_0),
   .rst_i_s8a(reset),
   .we_i_s8a(we & code_space),
   .dat_o_s16b(risc_prog_dat),
   .dat_i_s16b(16'b0),           // Processor only reads instruction words...
   .adr_i_s16b(risc_prog_adr[9:0]),
   .clk_i_s16b(sys_clk_0),
   .rst_i_s16b(reset),
   .we_i_s16b(1'b0)              // Processor only reads instruction words...
   );
  


// 12k of 3-bit RAM (12288 x 3)
// Each location corresponds to one pixel on a display of 128x96 pixels.
// Each data word [2:0] is blue,green,red.
assign dat[2:0] = (rgb_space && ~we)?rgb_ram_dat_o:{3{1'bZ}};

ramb12_s3_s3
  rgb_space_ram
  (
   .dat_o_s3a(rgb_ram_dat_o),
   .dat_i_s3a(dat[2:0]),
   .adr_i_s3a(adr[13:0]),
   .clk_i_s3a(sys_clk_0),
   .rst_i_s3a(reset),
   .we_i_s3a(we & rgb_space),
   .dat_o_s3b(pixel_dat),
   .dat_i_s3b(3'b000),           // Display only reads pixel data...
   .adr_i_s3b(pixel_adr),
   .clk_i_s3b(sys_clk_0),
   .rst_i_s3b(reset),
   .we_i_s3b(1'b0)               // Display only reads pixel data...
   );

// 512 bytes of register file RAM for the risc16f84 processor.
// These are memory mapped into the AUX bus on the A port of the RAM,
// to facilitate debugging (One can examine the contents of registers from
// the rs232_syscon command prompt!)
assign dat = (ram_space && ~we)?regfile_ram_dat_o:{8{1'bZ}};

RAMB4_S8_S8 
  risc16f84_regs 
  (
  .DOA(regfile_ram_dat_o),
  .DIA(dat),
  .ADDRA(adr[8:0]),
  .CLKA(sys_clk_0),
  .ENA(ram_space),
  .RSTA(reset),
  .WEA(we),
  .DOB(risc_ram_dat_i),
  .DIB(risc_ram_dat_o),
  .ADDRB(risc_ram_adr),
  .CLKB(sys_clk_0),
  .ENB(1'b1),
  .RSTB(reset),
  .WEB(risc_ram_we)
  );



//--------------------------------------------------------------------------
// Module code
//--------------------------------------------------------------------------


endmodule