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/*
* PS2 Mouse Interface
* Copyright (C) 2010 Donna Polehn <dpolehn@verizon.net>
*
* This file is part of the Zet processor. This processor is free
* hardware; you can redistribute it and/or modify it under the terms of
* the GNU General Public License as published by the Free Software
* Foundation; either version 3, or (at your option) any later version.
*
* Zet is distrubuted in the hope that it will be useful, but WITHOUT
* ANY WARRANTY; without even the implied warranty of MERCHANTABILITY
* or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public
* License for more details.
*
* You should have received a copy of the GNU General Public License
* along with Zet; see the file COPYING. If not, see
* <http://www.gnu.org/licenses/>.
*/
module ps2_mouse (
input clk, // Clock Input
input reset, // Reset Input
inout ps2_clk, // PS2 Clock, Bidirectional
inout ps2_dat, // PS2 Data, Bidirectional
input [7:0] the_command, // Command to send to mouse
input send_command, // Signal to send
output command_was_sent, // Signal command finished sending
output error_communication_timed_out,
output [7:0] received_data, // Received data
output received_data_en, // If 1 - new data has been received
output start_receiving_data,
output wait_for_incoming_data
);
// --------------------------------------------------------------------
// Internal wires and registers Declarations
// --------------------------------------------------------------------
wire ps2_clk_posedge; // Internal Wires
wire ps2_clk_negedge;
reg [7:0] idle_counter; // Internal Registers
reg ps2_clk_reg;
reg ps2_data_reg;
reg last_ps2_clk;
reg [2:0] ns_ps2_transceiver; // State Machine Registers
reg [2:0] s_ps2_transceiver;
// --------------------------------------------------------------------
// Constant Declarations
// --------------------------------------------------------------------
localparam PS2_STATE_0_IDLE = 3'h0, // states
PS2_STATE_1_DATA_IN = 3'h1,
PS2_STATE_2_COMMAND_OUT = 3'h2,
PS2_STATE_3_END_TRANSFER = 3'h3,
PS2_STATE_4_END_DELAYED = 3'h4;
// --------------------------------------------------------------------
// Finite State Machine(s)
// --------------------------------------------------------------------
always @(posedge clk) begin
if(reset == 1'b1) s_ps2_transceiver <= PS2_STATE_0_IDLE;
else s_ps2_transceiver <= ns_ps2_transceiver;
end
always @(*) begin
ns_ps2_transceiver = PS2_STATE_0_IDLE; // Defaults
case (s_ps2_transceiver)
PS2_STATE_0_IDLE:
begin
if((idle_counter == 8'hFF) && (send_command == 1'b1))
ns_ps2_transceiver = PS2_STATE_2_COMMAND_OUT;
else if ((ps2_data_reg == 1'b0) && (ps2_clk_posedge == 1'b1))
ns_ps2_transceiver = PS2_STATE_1_DATA_IN;
else ns_ps2_transceiver = PS2_STATE_0_IDLE;
end
PS2_STATE_1_DATA_IN:
begin
// if((received_data_en == 1'b1) && (ps2_clk_posedge == 1'b1))
if((received_data_en == 1'b1)) ns_ps2_transceiver = PS2_STATE_0_IDLE;
else ns_ps2_transceiver = PS2_STATE_1_DATA_IN;
end
PS2_STATE_2_COMMAND_OUT:
begin
if((command_was_sent == 1'b1) || (error_communication_timed_out == 1'b1))
ns_ps2_transceiver = PS2_STATE_3_END_TRANSFER;
else ns_ps2_transceiver = PS2_STATE_2_COMMAND_OUT;
end
PS2_STATE_3_END_TRANSFER:
begin
if(send_command == 1'b0) ns_ps2_transceiver = PS2_STATE_0_IDLE;
else if((ps2_data_reg == 1'b0) && (ps2_clk_posedge == 1'b1))
ns_ps2_transceiver = PS2_STATE_4_END_DELAYED;
else ns_ps2_transceiver = PS2_STATE_3_END_TRANSFER;
end
PS2_STATE_4_END_DELAYED:
begin
if(received_data_en == 1'b1) begin
if(send_command == 1'b0) ns_ps2_transceiver = PS2_STATE_0_IDLE;
else ns_ps2_transceiver = PS2_STATE_3_END_TRANSFER;
end
else ns_ps2_transceiver = PS2_STATE_4_END_DELAYED;
end
default:
ns_ps2_transceiver = PS2_STATE_0_IDLE;
endcase
end
// --------------------------------------------------------------------
// Sequential logic
// --------------------------------------------------------------------
always @(posedge clk) begin
if(reset == 1'b1) begin
last_ps2_clk <= 1'b1;
ps2_clk_reg <= 1'b1;
ps2_data_reg <= 1'b1;
end
else begin
last_ps2_clk <= ps2_clk_reg;
ps2_clk_reg <= ps2_clk;
ps2_data_reg <= ps2_dat;
end
end
always @(posedge clk) begin
if(reset == 1'b1) idle_counter <= 6'h00;
else if((s_ps2_transceiver == PS2_STATE_0_IDLE) && (idle_counter != 8'hFF))
idle_counter <= idle_counter + 6'h01;
else if (s_ps2_transceiver != PS2_STATE_0_IDLE)
idle_counter <= 6'h00;
end
// --------------------------------------------------------------------
// Combinational logic
// --------------------------------------------------------------------
assign ps2_clk_posedge = ((ps2_clk_reg == 1'b1) && (last_ps2_clk == 1'b0)) ? 1'b1 : 1'b0;
assign ps2_clk_negedge = ((ps2_clk_reg == 1'b0) && (last_ps2_clk == 1'b1)) ? 1'b1 : 1'b0;
assign start_receiving_data = (s_ps2_transceiver == PS2_STATE_1_DATA_IN);
assign wait_for_incoming_data = (s_ps2_transceiver == PS2_STATE_3_END_TRANSFER);
// --------------------------------------------------------------------
// Internal Modules
// --------------------------------------------------------------------
ps2_mouse_cmdout mouse_cmdout (
.clk (clk), // Inputs
.reset (reset),
.the_command (the_command),
.send_command (send_command),
.ps2_clk_posedge (ps2_clk_posedge),
.ps2_clk_negedge (ps2_clk_negedge),
.ps2_clk (ps2_clk), // Bidirectionals
.ps2_dat (ps2_dat),
.command_was_sent (command_was_sent), // Outputs
.error_communication_timed_out (error_communication_timed_out)
);
ps2_mouse_datain mouse_datain (
.clk (clk), // Inputs
.reset (reset),
.wait_for_incoming_data (wait_for_incoming_data),
.start_receiving_data (start_receiving_data),
.ps2_clk_posedge (ps2_clk_posedge),
.ps2_clk_negedge (ps2_clk_negedge),
.ps2_data (ps2_data_reg),
.received_data (received_data), // Outputs
.received_data_en (received_data_en)
);
endmodule
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