Subversion Repositories jt51

/*  This file is part of JT51.
 
    JT51 is free software: 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 of the License, or
    (at your option) any later version.
 
    JT51 is distributed 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 JT51.  If not, see <http://www.gnu.org/licenses/>.
 
	Author: Jose Tejada Gomez. Twitter: @topapate
	Version: 1.0
	Date: 27-10-2016
	*/
 
`timescale 1ns / 1ps
 
module jt51_pm(
	input	[6:0]	kc,
    input	[5:0]	kf,
    input	[8:0]	mod,
    input			add,
    output	reg [12:0] kcex
);
 
reg [9:0] lim;
reg [13:0] kcex0, kcex1;
reg [1:0] extra;
 
reg [6:0] kcin;
reg carry;
 
always @(*) begin: kc_input_cleaner
	{ carry, kcin } <= kc[1:0]==3'd3 ? { 1'b0, kc } + 8'd1 : {1'b0,kc};
end
 
always @(*) begin : addition
	lim <= { 1'd0, mod } +  { 4'd0, kf };
    case( kcin[3:0] )
		default:
        	if( lim>=10'd448 ) extra <= 2'd2;
            else if( lim>=10'd256 ) extra <= 2'd1;
            else extra <= 2'd0;
         4'd1,4'd5,4'd9,4'd13:
        	if( lim>=10'd384 ) extra <= 2'd2;
            else if( lim>=10'd192 ) extra <= 2'd1;
            else extra <= 2'd0;
         4'd2,4'd6,4'd10,4'd14:
        	if( lim>=10'd512 ) extra <= 2'd3;
        	else if( lim>=10'd320 ) extra <= 2'd2;
            else if( lim>=10'd128 ) extra <= 2'd1;
            else extra <= 2'd0;            
    endcase
    kcex0 <= {1'b0,kcin,kf} + { 4'd0, extra, 6'd0 } + { 1'd0, mod };
    kcex1 <= kcex0[7:6]==2'd3 ? kcex0 + 14'd64 : kcex0;    
end
 
reg signed [9:0] slim;
reg [1:0] sextra;
reg [13:0] skcex0, skcex1;
 
always @(*) begin : subtraction
	slim <= { 1'd0, mod } - { 4'd0, kf };
    case( kcin[3:0] )
		default:
        	if( slim>=10'sd449 ) sextra <= 2'd3;
        	else if( slim>=10'sd257 ) sextra <= 2'd2;
            else if( slim>=10'sd65 ) sextra <= 2'd1;
            else sextra <= 2'd0;
         4'd1,4'd5,4'd9,4'd13:
	        if( slim>=10'sd321 ) sextra <= 2'd2;
            else if( slim>=10'sd129 ) sextra <= 2'd1;
            else sextra <= 2'd0;
         4'd2,4'd6,4'd10,4'd14:
        	if( slim>=10'sd385 ) sextra <= 2'd2;
            else if( slim>=10'sd193 ) sextra <= 2'd1;
            else sextra <= 2'd0;            
    endcase
    skcex0 <= {1'b0,kcin,kf} - { 4'd0, sextra, 6'd0 } - { 1'd0, mod };
    skcex1 <= skcex0[7:6]==2'd3 ? skcex0 - 14'd64 : skcex0;
end
 
always @(*) begin : mux
	if ( add )
	    kcex  <= kcex1[13] | carry ? {3'd7, 4'd14, 6'd63} : kcex1[12:0];
    else
	    kcex  <= carry ? {3'd7, 4'd14, 6'd63} : (skcex1[13] ? 13'd0 : skcex1[12:0]);
end
 
endmodule