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// ============================================================================

//  Keyboard 

//  - Reads keys from PS2 style keyboard

//

//      2010-2011  Robert Finch

//      robfinch<remove>@FPGAfield.ca

//

//

//  This source code is available for evaluation and validation purposes

//  only. This copyright statement and disclaimer must remain present in

//  the file.

//

//

//      NO WARRANTY.

//  THIS Work, IS PROVIDEDED "AS IS" WITH NO WARRANTIES OF ANY KIND, WHETHER

//  EXPRESS OR IMPLIED. The user must assume the entire risk of using the

//  Work.

//

//  IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE FOR ANY

//  INCIDENTAL, CONSEQUENTIAL, OR PUNITIVE DAMAGES WHATSOEVER RELATING TO

//  THE USE OF THIS WORK, OR YOUR RELATIONSHIP WITH THE AUTHOR.

//

//  IN ADDITION, IN NO EVENT DOES THE AUTHOR AUTHORIZE YOU TO USE THE WORK

//  IN APPLICATIONS OR SYSTEMS WHERE THE WORK'S FAILURE TO PERFORM CAN

//  REASONABLY BE EXPECTED TO RESULT IN A SIGNIFICANT PHYSICAL INJURY, OR IN

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//

//

//      Convert a PS2 keyboard to ascii

//

//      Reg

//      $00             ascii code - bit 15 = strobe

//      $01             access this address clears keyboard strobe

//      

//

//      Verilog 1995

//      Webpack 9.2i  xc3s1200-4fg320

//      64 slices / 118 LUTs / 175.009 MHz

//  72 ff's / 2 BRAM (2048x16)

//

// ============================================================================

// PS2 scan codes

`define SC_LSHIFT       8'h12

`define SC_RSHIFT       8'h59

`define SC_CTRL         8'h14

`define SC_ALT          8'h11

`define SC_DEL          8'h71   // extend

`define SC_LCTRL        8'h58

`define SC_EXTEND       8'hE0

`define SC_KEYUP        8'hF0

module FF_PS2KbdToAscii(rst_i, clk_i, cyc_i, stb_i, ack_o, adr_i, dat_o, kclk, kd, irq, rst_o);

input rst_i;                            // reset

input clk_i;                            // master clock

input cyc_i;

input stb_i;

output ack_o;                           // ready

input [43:0] adr_i;                      // address

output [15:0] dat_o;             // data output

inout kclk;                             // keyboard clock from keyboard

tri kclk;

inout kd;                               // keyboard data

tri kd;

output irq;                             // data available

output rst_o;                   // reset output CTRL-ALT-DEL was pressed

wire cs = cyc_i && stb_i && (adr_i[43:4]==40'hFFF_FFDC_000);

reg strobe;

wire ps2_irq;

reg ps2_irq1;

reg ps2_cs;

wire [15:0] ps2_o;

// keyboard state

reg keyup;

reg extend;                             // extended keycode active

reg shift;                              // shift status

reg ctrl;                               // control status

reg alt;                                // alt status

reg x;

reg [7:0] sc;

assign ack_o = cs;

wire ign;

wire [7:0] xlat_o;

PS2ScanToAscii u1

(

        .shift(shift),

        .ctrl(ctrl),

        .alt(1'b0),

        .sc(sc),

        .extend(x),

        .ascii(xlat_o)

);

assign irq = strobe;

assign dat_o = cs ? {strobe,7'b0,xlat_o} : 16'h0000;

FF_PS2kbd u2

(

        .rst_i(rst_i),

        .clk_i(clk_i),

        .cyc_i(ps2_cs),

        .stb_i(ps2_cs),

        .ack_o(),

        .we_i(1'b0),

        .adr_i(44'hFFF_FFDC_0000),

        .dat_i(16'h0000),

        .dat_o(ps2_o),

        .vol_o(),

        .irq(ps2_irq),

        .kclk(kclk),

        .kd(kd)

);

// This little machine takes care of issuing a read cycle to the ps2 keyboard

// when data is present.

always @(posedge clk_i)

        if (rst_i) begin

                ps2_cs <= 0;

                ps2_irq1 <= 0;

        end

        else begin

                // has an PS2 keyboard event happened ?

                // If so, read the ps2 port

                ps2_irq1 <= ps2_irq;

                if (ps2_irq & ~ps2_irq1)

                        ps2_cs <= 1;

                else

                        ps2_cs <= 0;

        end

// This machine

// 1) clears the strobe line on an access to the keyboard strobe clear address

// 2) activates the strobe on a keydown event, filtering out special keys

// like control and alt

// 3) captures the state of ctrl,alt and shift and filters these codes out

always @(posedge clk_i)

        if (rst_i) begin

                keyup <= 0;

                extend <= 0;

                shift <= 0;

                ctrl <= 0;

                alt <= 0;

                sc <= 0;

                x <= 1'b0;

                strobe <= 0;

        end

        else begin

                if (cs & adr_i[1])

                        strobe <= 0;

                if (ps2_cs) begin

                        case (ps2_o[7:0])

                        `SC_KEYUP:      keyup <= 1;

                        `SC_EXTEND:     extend <= 1;

                        default:

                                begin

                                case(ps2_o[7:0])

                                `SC_CTRL:       ctrl <= ~keyup;

                                `SC_ALT:        alt <= ~keyup;

                                `SC_LSHIFT,

                                `SC_RSHIFT:     shift <= ~keyup;

                                default:

                                        begin

                                        sc <= ps2_o;

                                        x <= extend;

                                        strobe <= keyup ? strobe : 1;

                                        end

                                endcase

                                keyup <= 0;

                                extend <= 0;

                                end

                        endcase

                end

        end

// CTRL-ALT-DEL

assign rst_o = ps2_o[7:0]==`SC_DEL && alt && ctrl;

endmodule