mirror of
https://github.com/MiSTer-devel/QL_MiSTer.git
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123 lines
2.8 KiB
Verilog
123 lines
2.8 KiB
Verilog
//
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// qimi.v - Ql mouse Interface
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//
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// Sinclair QL for the MiST
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// https://github.com/mist-devel
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//
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// Copyright (c) 2015 Till Harbaum <till@harbaum.org>
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//
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// This source file is free software: you can redistribute it and/or modify
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// it under the terms of the GNU General Public License as published
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// by the Free Software Foundation, either version 3 of the License, or
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// (at your option) any later version.
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//
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// This source file is distributed in the hope that it will be useful,
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// but WITHOUT ANY WARRANTY; without even the implied warranty of
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// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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// GNU General Public License for more details.
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//
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// You should have received a copy of the GNU General Public License
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// along with this program. If not, see <http://www.gnu.org/licenses/>.
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//
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module qimi
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(
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input clk,
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input cen,
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input cep,
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input reset,
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input cpu_sel,
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input [1:0] cpu_addr, // a5, a1
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output [7:0] cpu_data,
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output reg irq,
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input [24:0] ps2_mouse
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);
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// generate irq ack whenever cpu accesses 1bf9c
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reg irq_ack;
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always @(posedge clk) begin
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if(cen) begin
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irq_ack <= 1'b0;
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if(cpu_sel && cpu_addr == 2'b11)
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irq_ack <= 1'b1;
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end
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end
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wire x_dir = !x_pos[9];
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wire y_dir = !y_pos[9];
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wire x_mov = (x_pos != 0);
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wire y_mov = (y_pos != 0);
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assign cpu_data =
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(cpu_addr == 2'b00)?{2'b00,!b[0],!b[1],4'b0000}: // 1bf9c
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(cpu_addr == 2'b10)?{2'b00,y_mov,x_dir,1'b0,x_mov,1'b0,y_dir }: // 1bfbc
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8'h00;
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// registers keeping state of current mouse state
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reg [1:0] b;
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reg [9:0] x_pos;
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reg [9:0] y_pos;
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// counter to limit irq rate to 2khz
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reg [11:0] irq_holdoff;
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always @(posedge clk) begin
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reg old_stb;
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if(cep) begin
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old_stb <= ps2_mouse[24];
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if(reset) begin
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x_pos <= 10'd0;
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y_pos <= 10'd0;
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irq <= 1'b0;
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irq_holdoff <= 12'd0;
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end else begin
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// check if we have to fire another irq
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if(irq_holdoff != 0) begin
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irq_holdoff <= irq_holdoff - 12'd1;
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if((irq_holdoff == 1) && (x_mov || y_mov))
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irq <= 1'b1;
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end
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if(old_stb != ps2_mouse[24]) begin
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b <= ps2_mouse[1:0];
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// the ps2 packet contains a 9 bit value. We only use the upper
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// 7. Otherwise the mouse would be too fast for our low resolution
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x_pos <= x_pos + { {2{ps2_mouse[4]}}, ps2_mouse[15:8]};
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y_pos <= y_pos + { {2{ps2_mouse[5]}}, ps2_mouse[23:16]};
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if(irq_holdoff == 0)
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irq_holdoff <= 12'd1;
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end else begin
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// one bit has been reported to host
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if(irq_ack) begin
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if(x_pos != 0) begin
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if(x_pos[9]) x_pos <= x_pos + 10'd1;
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else x_pos <= x_pos - 10'd1;
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end
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if(y_pos != 0) begin
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if(y_pos[9]) y_pos <= y_pos + 10'd1;
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else y_pos <= y_pos - 10'd1;
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end
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// clear irq
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irq <= 1'b0;
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// next irq after some time ...
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irq_holdoff <= 12'd4000;
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end
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end
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end
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end
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end
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endmodule
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