tap_top.v

verilog 实现的jtag ip模块 包括了测试程序

  if(~tms_pad_i & (exit1_dr | pause_dr))
    pause_dr<=#1 1'b1;
  else
    pause_dr<=#1 1'b0;
end

// exit2_dr state
always @ (posedge tck_pad_i or posedge trst_pad_i)
begin
  if(trst_pad_i)
    exit2_dr<=#1 1'b0;
  else if (tms_reset)
    exit2_dr<=#1 1'b0;
  else
  if(tms_pad_i & pause_dr)
    exit2_dr<=#1 1'b1;
  else
    exit2_dr<=#1 1'b0;
end

// update_dr state
always @ (posedge tck_pad_i or posedge trst_pad_i)
begin
  if(trst_pad_i)
    update_dr<=#1 1'b0;
  else if (tms_reset)
    update_dr<=#1 1'b0;
  else
  if(tms_pad_i & (exit1_dr | exit2_dr))
    update_dr<=#1 1'b1;
  else
    update_dr<=#1 1'b0;
end

// select_ir_scan state
always @ (posedge tck_pad_i or posedge trst_pad_i)
begin
  if(trst_pad_i)
    select_ir_scan<=#1 1'b0;
  else if (tms_reset)
    select_ir_scan<=#1 1'b0;
  else
  if(tms_pad_i & select_dr_scan)
    select_ir_scan<=#1 1'b1;
  else
    select_ir_scan<=#1 1'b0;
end

// capture_ir state
always @ (posedge tck_pad_i or posedge trst_pad_i)
begin
  if(trst_pad_i)
    capture_ir<=#1 1'b0;
  else if (tms_reset)
    capture_ir<=#1 1'b0;
  else
  if(~tms_pad_i & select_ir_scan)
    capture_ir<=#1 1'b1;
  else
    capture_ir<=#1 1'b0;
end

// shift_ir state
always @ (posedge tck_pad_i or posedge trst_pad_i)
begin
  if(trst_pad_i)
    shift_ir<=#1 1'b0;
  else if (tms_reset)
    shift_ir<=#1 1'b0;
  else
  if(~tms_pad_i & (capture_ir | shift_ir | exit2_ir))
    shift_ir<=#1 1'b1;
  else
    shift_ir<=#1 1'b0;
end

// exit1_ir state
always @ (posedge tck_pad_i or posedge trst_pad_i)
begin
  if(trst_pad_i)
    exit1_ir<=#1 1'b0;
  else if (tms_reset)
    exit1_ir<=#1 1'b0;
  else
  if(tms_pad_i & (capture_ir | shift_ir))
    exit1_ir<=#1 1'b1;
  else
    exit1_ir<=#1 1'b0;
end

// pause_ir state
always @ (posedge tck_pad_i or posedge trst_pad_i)
begin
  if(trst_pad_i)
    pause_ir<=#1 1'b0;
  else if (tms_reset)
    pause_ir<=#1 1'b0;
  else
  if(~tms_pad_i & (exit1_ir | pause_ir))
    pause_ir<=#1 1'b1;
  else
    pause_ir<=#1 1'b0;
end

// exit2_ir state
always @ (posedge tck_pad_i or posedge trst_pad_i)
begin
  if(trst_pad_i)
    exit2_ir<=#1 1'b0;
  else if (tms_reset)
    exit2_ir<=#1 1'b0;
  else
  if(tms_pad_i & pause_ir)
    exit2_ir<=#1 1'b1;
  else
    exit2_ir<=#1 1'b0;
end

// update_ir state
always @ (posedge tck_pad_i or posedge trst_pad_i)
begin
  if(trst_pad_i)
    update_ir<=#1 1'b0;
  else if (tms_reset)
    update_ir<=#1 1'b0;
  else
  if(tms_pad_i & (exit1_ir | exit2_ir))
    update_ir<=#1 1'b1;
  else
    update_ir<=#1 1'b0;
end

/**********************************************************************************
*                                                                                 *
*   End: TAP State Machine                                                        *
*                                                                                 *
**********************************************************************************/



/**********************************************************************************
*                                                                                 *
*   jtag_ir:  JTAG Instruction Register                                           *
*                                                                                 *
**********************************************************************************/
reg [`IR_LENGTH-1:0]  jtag_ir;          // Instruction register
reg [`IR_LENGTH-1:0]  latched_jtag_ir, latched_jtag_ir_neg;
reg                   instruction_tdo;

always @ (posedge tck_pad_i or posedge trst_pad_i)
begin
  if(trst_pad_i)
    jtag_ir[`IR_LENGTH-1:0] <= #1 `IR_LENGTH'b0;
  else if(capture_ir)
    jtag_ir <= #1 4'b0000;          // This value is fixed for easier fault detection
  else if(shift_ir)
    jtag_ir[`IR_LENGTH-1:0] <= #1 {tdi_pad_i, jtag_ir[`IR_LENGTH-1:1]};
end

always @ (negedge tck_pad_i)
begin
  instruction_tdo <= #1 jtag_ir[0];
end
/**********************************************************************************
*                                                                                 *
*   End: jtag_ir                                                                  *
*                                                                                 *
**********************************************************************************/



/**********************************************************************************
*                                                                                 *
*   idcode logic                                                                  *
*                                                                                 *
**********************************************************************************/
reg [31:0] idcode_reg;
reg        idcode_tdo;

always @ (posedge tck_pad_i)
begin
  if(idcode_select & shift_dr)
    idcode_reg <= #1 {tdi_pad_i, idcode_reg[31:1]};
  else
    idcode_reg <= #1 `IDCODE_VALUE;
end

always @ (negedge tck_pad_i)
begin
    idcode_tdo <= #1 idcode_reg;//idcode_tdo<=#1 idcode_reg[0];
end
/**********************************************************************************
*                                                                                 *
*   End: idcode logic                                                             *
*                                                                                 *
**********************************************************************************/


/**********************************************************************************
*                                                                                 *
*   Bypass logic                                                                  *
*                                                                                 *
**********************************************************************************/
reg  bypassed_tdo;
reg  bypass_reg;

always @ (posedge tck_pad_i or posedge trst_pad_i)
begin
  if (trst_pad_i)
    bypass_reg<=#1 1'b0;
  else if(shift_dr)
    bypass_reg<=#1 tdi_pad_i;
end

always @ (negedge tck_pad_i)
begin
  bypassed_tdo <=#1 bypass_reg;
end
/**********************************************************************************
*                                                                                 *
*   End: Bypass logic                                                             *
*                                                                                 *
**********************************************************************************/


/**********************************************************************************
*                                                                                 *
*   Activating Instructions                                                       *
*                                                                                 *
**********************************************************************************/
// Updating jtag_ir (Instruction Register)
always @ (posedge tck_pad_i or posedge trst_pad_i)
begin
  if(trst_pad_i)
    latched_jtag_ir <=#1 `IDCODE;   // IDCODE selected after reset
  else if (tms_reset)
    latched_jtag_ir <=#1 `IDCODE;   // IDCODE selected after reset
  else if(update_ir)
    latched_jtag_ir <=#1 jtag_ir;
end

/**********************************************************************************
*                                                                                 *
*   End: Activating Instructions                                                  *
*                                                                                 *
**********************************************************************************/


// Updating jtag_ir (Instruction Register)
always @ (latched_jtag_ir)
begin
  extest_select           = 1'b0;
  sample_preload_select   = 1'b0;
  idcode_select           = 1'b0;
  mbist_select            = 1'b0;
  debug_select            = 1'b0;
  bypass_select           = 1'b0;

  case(latched_jtag_ir)    /* synthesis parallel_case */ 
    `EXTEST:            extest_select           = 1'b1;    // External test
    `SAMPLE_PRELOAD:    sample_preload_select   = 1'b1;    // Sample preload
    `IDCODE:            idcode_select           = 1'b1;    // ID Code
    `MBIST:             mbist_select            = 1'b1;    // Mbist test
    `DEBUG:             debug_select            = 1'b1;    // Debug
    `BYPASS:            bypass_select           = 1'b1;    // BYPASS
    default:            bypass_select           = 1'b1;    // BYPASS
  endcase
end



/**********************************************************************************
*                                                                                 *
*   Multiplexing TDO data                                                         *
*                                                                                 *
**********************************************************************************/
always @ (shift_ir_neg or exit1_ir or instruction_tdo or latched_jtag_ir_neg or idcode_tdo or
          debug_tdi_i or bs_chain_tdi_i or mbist_tdi_i or 
          bypassed_tdo)
begin
  if(shift_ir_neg)
    tdo_pad_o = instruction_tdo;
  else
    begin
      case(latched_jtag_ir_neg)    // synthesis parallel_case
        `IDCODE:            tdo_pad_o = idcode_tdo;       // Reading ID code
        `DEBUG:             tdo_pad_o = debug_tdi_i;      // Debug
        `SAMPLE_PRELOAD:    tdo_pad_o = bs_chain_tdi_i;   // Sampling/Preloading
        `EXTEST:            tdo_pad_o = bs_chain_tdi_i;   // External test
        `MBIST:             tdo_pad_o = mbist_tdi_i;      // Mbist test
        default:            tdo_pad_o = bypassed_tdo;     // BYPASS instruction
      endcase
    end
end


// Tristate control for tdo_pad_o pin
always @ (negedge tck_pad_i)
begin
  tdo_padoe_o <= #1 shift_ir | shift_dr | (pause_dr & debug_select);
end
/**********************************************************************************
*                                                                                 *
*   End: Multiplexing TDO data                                                    *
*                                                                                 *
**********************************************************************************/


always @ (negedge tck_pad_i)
begin
  shift_ir_neg <= #1 shift_ir;
  latched_jtag_ir_neg <= #1 latched_jtag_ir;
end


endmodule