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//----------------------------------------------------------------------------

// Copyright (C) 2001 Authors

//

// This source file may be used and distributed without restriction provided

// that this copyright statement is not removed from the file and that any

// derivative work contains the original copyright notice and the associated

// disclaimer.

//

// This source file is free software; you can redistribute it and/or modify

// it under the terms of the GNU Lesser General Public License as published

// by the Free Software Foundation; either version 2.1 of the License, or

// (at your option) any later version.

//

// This source 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 Lesser General Public

// License for more details.

//

// You should have received a copy of the GNU Lesser General Public License

// along with this source; if not, write to the Free Software Foundation,

// Inc., 51 Franklin Street, Fifth Floor, Boston, MA  02110-1301  USA

//

//----------------------------------------------------------------------------

//

// *File Name: omsp_clock_module.v

// 

// *Module Description:

//                       Basic clock module implementation.

//                      Since the openMSP430 mainly targets FPGA and hobby

//                     designers. The clock structure has been greatly

//                     symplified in order to ease integration.

//                      See online wiki for more info.

//

// *Author(s):

//              - Olivier Girard,    olgirard@gmail.com

//

//----------------------------------------------------------------------------

// $Rev: 106 $

// $LastChangedBy: olivier.girard $

// $LastChangedDate: 2011-03-25 23:01:03 +0100 (Fri, 25 Mar 2011) $

//----------------------------------------------------------------------------

`ifdef OMSP_NO_INCLUDE

`else

`include "openMSP430_defines.v"

`endif

module  omsp_clock_module (

// OUTPUTs

    aclk_en,                      // ACLK enable

    cpu_en_s,                     // Enable CPU code execution (synchronous)

    dbg_clk,                      // Debug unit clock

    dbg_en_s,                     // Debug interface enable (synchronous)

    dbg_rst,                      // Debug unit reset

    mclk,                         // Main system clock

    per_dout,                     // Peripheral data output

    por,                          // Power-on reset

    puc,                          // Main system reset

    smclk_en,                     // SMCLK enable

// INPUTs

    cpu_en,                       // Enable CPU code execution (asynchronous)

    dbg_cpu_reset,                // Reset CPU from debug interface

    dbg_en,                       // Debug interface enable (asynchronous)

    dco_clk,                      // Fast oscillator (fast clock)

    lfxt_clk,                     // Low frequency oscillator (typ 32kHz)

    oscoff,                       // Turns off LFXT1 clock input

    per_addr,                     // Peripheral address

    per_din,                      // Peripheral data input

    per_en,                       // Peripheral enable (high active)

    per_we,                       // Peripheral write enable (high active)

    reset_n,                      // Reset Pin (low active, asynchronous)

    scg1,                         // System clock generator 1. Turns off the SMCLK

    wdt_reset                     // Watchdog-timer reset

);

// OUTPUTs

//=========

output              aclk_en;      // ACLK enable

output              cpu_en_s;     // Enable CPU code execution (synchronous)

output              dbg_clk;      // Debug unit clock

output              dbg_en_s;     // Debug unit enable (synchronous)

output              dbg_rst;      // Debug unit reset

output              mclk;         // Main system clock

output       [15:0] per_dout;     // Peripheral data output

output              por;          // Power-on reset

output              puc;          // Main system reset

output              smclk_en;     // SMCLK enable

// INPUTs

//=========

input               cpu_en;       // Enable CPU code execution (asynchronous)

input               dbg_cpu_reset;// Reset CPU from debug interface

input               dbg_en;       // Debug interface enable (asynchronous)

input               dco_clk;      // Fast oscillator (fast clock)

input               lfxt_clk;     // Low frequency oscillator (typ 32kHz)

input               oscoff;       // Turns off LFXT1 clock input

input         [7:0] per_addr;     // Peripheral address

input        [15:0] per_din;      // Peripheral data input

input               per_en;       // Peripheral enable (high active)

input         [1:0] per_we;       // Peripheral write enable (high active)

input               reset_n;      // Reset Pin (low active, asynchronous)

input               scg1;         // System clock generator 1. Turns off the SMCLK

input               wdt_reset;    // Watchdog-timer reset

//=============================================================================

// 1)  PARAMETER DECLARATION

//=============================================================================

// Register addresses

parameter           BCSCTL1    = 9'h057;

parameter           BCSCTL2    = 9'h058;

// Register one-hot decoder

parameter           BCSCTL1_D  = (256'h1 << (BCSCTL1 /2));

parameter           BCSCTL2_D  = (256'h1 << (BCSCTL2 /2));

//============================================================================

// 2)  REGISTER DECODER

//============================================================================

// Register address decode

reg  [255:0]  reg_dec;

always @(per_addr)

  case (per_addr)

    (BCSCTL1 /2):     reg_dec  =  BCSCTL1_D;

    (BCSCTL2 /2):     reg_dec  =  BCSCTL2_D;

    default     :     reg_dec  =  {256{1'b0}};

  endcase

// Read/Write probes

wire         reg_lo_write =  per_we[0] & per_en;

wire         reg_hi_write =  per_we[1] & per_en;

wire         reg_read     = ~|per_we   & per_en;

// Read/Write vectors

wire [255:0] reg_hi_wr    = reg_dec & {256{reg_hi_write}};

wire [255:0] reg_lo_wr    = reg_dec & {256{reg_lo_write}};

wire [255:0] reg_rd       = reg_dec & {256{reg_read}};

//============================================================================

// 3) REGISTERS

//============================================================================

// BCSCTL1 Register

//--------------

reg  [7:0] bcsctl1;

wire       bcsctl1_wr  = BCSCTL1[0] ? reg_hi_wr[BCSCTL1/2] : reg_lo_wr[BCSCTL1/2];

wire [7:0] bcsctl1_nxt = BCSCTL1[0] ? per_din[15:8]        : per_din[7:0];

always @ (posedge mclk or posedge puc)

  if (puc)              bcsctl1  <=  8'h00;

  else if (bcsctl1_wr)  bcsctl1  <=  bcsctl1_nxt & 8'h30; // Mask unused bits

// BCSCTL2 Register

//--------------

reg  [7:0] bcsctl2;

wire       bcsctl2_wr  = BCSCTL2[0] ? reg_hi_wr[BCSCTL2/2] : reg_lo_wr[BCSCTL2/2];

wire [7:0] bcsctl2_nxt = BCSCTL2[0] ? per_din[15:8]        : per_din[7:0];

always @ (posedge mclk or posedge puc)

  if (puc)              bcsctl2  <=  8'h00;

  else if (bcsctl2_wr)  bcsctl2  <=  bcsctl2_nxt & 8'h0e; // Mask unused bits

//============================================================================

// 4) DATA OUTPUT GENERATION

//============================================================================

// Data output mux

wire [15:0] bcsctl1_rd   = {8'h00, (bcsctl1  & {8{reg_rd[BCSCTL1/2]}})}  << (8 & {4{BCSCTL1[0]}});

wire [15:0] bcsctl2_rd   = {8'h00, (bcsctl2  & {8{reg_rd[BCSCTL2/2]}})}  << (8 & {4{BCSCTL2[0]}});

wire [15:0] per_dout =  bcsctl1_rd   |

                        bcsctl2_rd;

//=============================================================================

// 5)  CLOCK GENERATION

//=============================================================================

// Synchronize CPU_EN signal

//---------------------------------------

reg  [1:0] cpu_en_sync;

always @ (posedge mclk or posedge por)

  if (por) cpu_en_sync <=  2'b00;

  else     cpu_en_sync <=  {cpu_en_sync[0], cpu_en};

assign     cpu_en_s     =   cpu_en_sync[1];

// Synchronize LFXT_CLK & edge detection

//---------------------------------------

reg  [2:0] lfxt_clk_s;

always @ (posedge mclk or posedge por)

  if (por) lfxt_clk_s <=  3'b000;

  else     lfxt_clk_s <=  {lfxt_clk_s[1:0], lfxt_clk};

wire lfxt_clk_en = (lfxt_clk_s[1] & ~lfxt_clk_s[2]) & ~(oscoff & ~bcsctl2[`SELS]);

// Generate main system clock

//----------------------------

wire  mclk   =  dco_clk;

wire  mclk_n = !dco_clk;

// Generate ACLK

//----------------------------

reg       aclk_en;

reg [2:0] aclk_div;

wire      aclk_en_nxt = lfxt_clk_en & ((bcsctl1[`DIVAx]==2'b00) ?  1'b1          :

                                       (bcsctl1[`DIVAx]==2'b01) ?  aclk_div[0]   :

                                       (bcsctl1[`DIVAx]==2'b10) ? &aclk_div[1:0] :

                                                                  &aclk_div[2:0]);

always @ (posedge mclk or posedge puc)

  if (puc)  aclk_en <=  1'b0;

  else      aclk_en <=  aclk_en_nxt & cpu_en_s;

always @ (posedge mclk or posedge puc)

  if (puc)                                         aclk_div <=  3'h0;

  else if ((bcsctl1[`DIVAx]!=2'b00) & lfxt_clk_en) aclk_div <=  aclk_div+3'h1;

// Generate SMCLK

//----------------------------

reg       smclk_en;

reg [2:0] smclk_div;

wire      smclk_in     = ~scg1 & (bcsctl2[`SELS] ? lfxt_clk_en : 1'b1);

wire      smclk_en_nxt = smclk_in & ((bcsctl2[`DIVSx]==2'b00) ?  1'b1           :

                                     (bcsctl2[`DIVSx]==2'b01) ?  smclk_div[0]   :

                                     (bcsctl2[`DIVSx]==2'b10) ? &smclk_div[1:0] :

                                                                &smclk_div[2:0]);

always @ (posedge mclk or posedge puc)

  if (puc)  smclk_en <=  1'b0;

  else      smclk_en <=  smclk_en_nxt & cpu_en_s;

always @ (posedge mclk or posedge puc)

  if (puc)                                      smclk_div <=  3'h0;

  else if ((bcsctl2[`DIVSx]!=2'b00) & smclk_in) smclk_div <=  smclk_div+3'h1;

// Generate DBG_CLK

//----------------------------

assign  dbg_clk = mclk;

//=============================================================================

// 6)  RESET GENERATION

//=============================================================================

// Generate synchronized POR

wire      por_reset_a  =  !reset_n;

reg [1:0] por_s;

always @(posedge mclk or posedge por_reset_a)

  if (por_reset_a) por_s  <=  2'b11;

  else             por_s  <=  {por_s[0], 1'b0};

wire   por = por_s[1];

// Generate main system reset

wire      puc_reset  = por | wdt_reset | dbg_cpu_reset;

reg [1:0] puc_s;

always @(posedge mclk or posedge puc_reset)

  if (puc_reset) puc_s  <=  2'b11;

  else           puc_s  <=  {puc_s[0], 1'b0};

wire   puc = puc_s[1];

// Generate debug unit reset

`ifdef DBG_EN

reg [1:0] dbg_rst_s;

always @(posedge mclk or posedge por)

  if (por) dbg_rst_s  <=  2'b11;

  else     dbg_rst_s  <=  {dbg_rst_s[0], ~dbg_en};

`else

wire [1:0] dbg_rst_s   = 2'b11;

`endif

wire   dbg_en_s = ~dbg_rst_s[1];

wire   dbg_rst  =  dbg_rst_s[1];

endmodule // omsp_clock_module

`ifdef OMSP_NO_INCLUDE

`else

`include "openMSP430_undefines.v"

`endif