Stepper Motor Controller Using MAX II CPLDs

[Altera_Forum]

I download AN 488(Stepper Motor Controller Using MAX II CPLDs) design example from the official website of ALTERA. 

 the following is the code   /********************************************************************************************************************* * Stepper motor Controller * December 2006 *********************************************************************************************************************/ //TOP LEVEL MODULE module stepmot(reset,dir,mode,move,phaseout); //module stepmot is the top level module. input reset,mode,dir,move; //reset when asserted brings the shaft to reference position. output phaseout; //mode specifies step operation or continuous operation. wire osc,clk; //dir is for clockwise or anti clockwise motion. wire oscena; //move shifts the shaft by half step in step mode. assign oscena=1'b1; /* Instantiation of ufmclk module. */ ufmclk ufmclk1( .oscena (oscena), .osc (osc)); /* Instantiation of clk divider module.*/ divider d1( .osc (osc), .clk (clk)); /* Instantiation of controller module.*/ stepper s1( .clk (clk), .reset (reset), .dir (dir), .mode (mode), .move (move), .phaseout (phaseout)); endmodule /* Module stepper is the motor controller module */ module stepper (clk,reset,dir,mode,move,phaseout); input clk,reset,dir,mode; input move; output phaseout; reg phaseout,position; always@(posedge clk or negedge reset) begin if(reset==0) begin // motor resets to 0111 at reset=0 phaseout=4'b0111; end else begin /* Mode=0 for continous motion */ if (mode==0) begin //dir=0 for anticlockwise motion case({phaseout}) //dir=1 for clockwise motion 4'b0111 : if (dir==0) phaseout=4'b0110; else phaseout=4'b0011; 4'b0011 : if(dir==0) phaseout=4'b0111; else phaseout=4'b1011; 4'b1011 : if (dir==0) phaseout=4'b0011; else phaseout=4'b1001; 4'b1001 : if (dir==0) phaseout=4'b1011; else phaseout=4'b1101; 4'b1101 : if (dir==0) phaseout=4'b1001; else phaseout=4'b1100; 4'b1100 : if (dir==0) phaseout=4'b1101; else phaseout=4'b1110; 4'b1110 : if (dir==0) phaseout=4'b1100; else phaseout=4'b0110; 4'b0110: if (dir==0) phaseout=4'b1110; else phaseout=4'b0111; default: $display("inavlid input"); endcase /* Mode=1 for step motion */ end else begin if(move==1'b0) begin case ({position}) 4'b0111 : if (dir==0) phaseout=4'b0110; else phaseout=4'b0011; 4'b0011 : if(dir==0) phaseout=4'b0111; else phaseout=4'b1011; 4'b1011 : if (dir==0) phaseout=4'b0011; else phaseout=4'b1001; 4'b1001 : if (dir==0) phaseout=4'b1011; else phaseout=4'b1101; 4'b1101 : if (dir==0) phaseout=4'b1001; else phaseout=4'b1100; 4'b1100 : if (dir==0) phaseout=4'b1101; else phaseout=4'b1110; 4'b1110 : if (dir==0) phaseout=4'b1100; else phaseout=4'b0110; 4'b0110 : if (dir==0) phaseout=4'b1110; else phaseout=4'b0111; default: $display("inavlid input"); endcase end end end end /* Motor moves half step on the negetive edge of move*/ always@(negedge move or negedge reset) begin if (reset==0) position=4'b0000; else if(reset==1) position=phaseout; end endmodule /******************************************************************************************* Module ufmclk is the module which gets the clock from the oscillator ******************************************************************************************/ `timescale 1 ps / 1 ps //synopsys translate_on module ufmclk_altufm_osc_7p3 ( osc, oscena) /* synthesis synthesis_clearbox=1 */; output osc; input oscena; wire wire_maxii_ufm_block1_osc; maxii_ufm maxii_ufm_block1 ( .arclk(1'b0), .ardin(1'b0), .arshft(1'b0), .bgpbusy(), .busy(), .drclk(1'b0), .drdout(), .drshft(1'b0), .osc(wire_maxii_ufm_block1_osc), .oscena(oscena) `ifdef FORMAL_VERIFICATION `else // synopsys translate_off `endif , .drdin(1'b0), .erase(1'b0), .program(1'b0) `ifdef FORMAL_VERIFICATION `else // synopsys translate_on `endif // synopsys translate_off , .ctrl_bgpbusy(), .devclrn(), .devpor(), .sbdin(), .sbdout() // synopsys translate_on ); defparam maxii_ufm_block1.address_width = 9, maxii_ufm_block1.osc_sim_setting = 180000, maxii_ufm_block1.lpm_type = "maxii_ufm"; assign osc = wire_maxii_ufm_block1_osc; endmodule //ufmclk_altufm_osc_7p3 //VALID FILE // synopsys translate_off `timescale 1 ps / 1 ps // synopsys translate_on module ufmclk ( oscena, osc)/* synthesis synthesis_clearbox = 1 */; input oscena; output osc; wire sub_wire0; wire osc = sub_wire0; ufmclk_altufm_osc_7p3 ufmclk_altufm_osc_7p3_component ( .oscena (oscena), .osc (sub_wire0)); endmodule /************************************************************************************************** * Module divider divides the clock from ufmclk to produce * a clock suitable to drive the motor controller *************************************************************************************************/ module divider (osc, clk); input osc; output clk; reg clk; reg count; initial count=17'b00000000000000000; always @( posedge osc) begin count = count + 1; clk = count; end endmodule /***********************************END OF PROGRAM.**********************************************/ But I can't understand the codes from the 140 line to the 179 line? what is the function of these codes? can you explain the meaning of the codes ?   can the 'initial ' synthesis in the verilog!