/*******************************************************************************
 **						         c : CelLogic, 1996
 **
 ** The information contained herein is proprietary of CelLogic.
 ** Any reproduction, in whole or part, disclosure, or use of this code is
 ** expressly prohibited except as specified in writing by CelLogic.
 ****************************************************************************
 **                                                                             
 **                                                                             
 ** Project Name         : DDS                                            
 **                                                                             
 ** Author               : Daniel J. Morelli
 ** Creation Date        : 03/04/96 20:33:07                                              
 ** Version Number       : 1.0                                                 
 **                                                                             
 ** Revision History     :                                                      
 **                                                                             
 ** Date          Initials         Modification                                 
 **                                                                             
 **                                                                             
 ** Description          :                                                      
 **                                                                             
 ** This block takes the phase angle value and outputs the sin wave
 ** value to the DAC.  This module looks up the sin wave values stored
 ** as a 1/4 sin wave in the romtab module.
 ** 
 **                                                                             
 *******************************************************************************/

 module sinlup (
	SYSCLK,			// system clock input
	RESETN,			// global reset
	MODPHASE,		// modulated phase output
	DACOUT);			// DAC output of sin wave

// Port types

input SYSCLK, RESETN;
input[7:0] MODPHASE;

output[7:0] DACOUT;

reg[5:0] phaseadd;	// 1/4 wave phase address to ROM table
reg modphase_msb1_ff;		// modulated phase MSB
reg modphase_msb2_ff;		// modulated phase MSB
reg[7:0] dac_ff;		// registered DAC output
wire[6:0] qwavesin;	// 1/4 wave sin value from ROM table
reg [6:0] qwavesin_ff;	// rom table output registered

// design architecture
	assign DACOUT = dac_ff;

  	romtab U_romtab(phaseadd, qwavesin);
 
   // get the phase angle for 1/4 rom table
	always @(posedge SYSCLK or negedge RESETN)
		if (!RESETN)
		begin
			phaseadd <= 6'h00;
			modphase_msb1_ff <= 0;
			modphase_msb2_ff <= 0;
			qwavesin_ff <= 7'h00;
			dac_ff <= 8'h00;
		end
		else
		begin
			modphase_msb1_ff <= MODPHASE[7];
			modphase_msb2_ff <= modphase_msb1_ff;
			qwavesin_ff <= qwavesin;
			if (MODPHASE[6])
				phaseadd <= ~MODPHASE[5:0];
			else
				phaseadd <= MODPHASE[5:0];
			dac_ff[7] <= ~modphase_msb2_ff;
			if (modphase_msb2_ff)
				dac_ff[6:0] <= ~qwavesin_ff;
			else
				dac_ff[6:0] <= qwavesin_ff;
		end


endmodule