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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: 111 $

// $LastChangedBy: olivier.girard $

// $LastChangedDate: 2011-05-20 22:39:02 +0200 (Fri, 20 May 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_rst,                      // 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_rst;      // 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        [13:0] 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 base address (must be aligned to decoder bit width)

parameter       [14:0] BASE_ADDR   = 15'h0050;

// Decoder bit width (defines how many bits are considered for address decoding)

parameter              DEC_WD      =  4;

// Register addresses offset

parameter [DEC_WD-1:0] BCSCTL1     =  'h7,

                       BCSCTL2     =  'h8;

// Register one-hot decoder utilities

parameter              DEC_SZ      =  2**DEC_WD;

parameter [DEC_SZ-1:0] BASE_REG    =  {{DEC_SZ-1{1'b0}}, 1'b1};

// Register one-hot decoder

parameter [DEC_SZ-1:0] BCSCTL1_D   = (BASE_REG << BCSCTL1),

                       BCSCTL2_D   = (BASE_REG << BCSCTL2);

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

// 2)  REGISTER DECODER

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

// Local register selection

wire              reg_sel      =  per_en & (per_addr[13:DEC_WD-1]==BASE_ADDR[14:DEC_WD]);

// Register local address

wire [DEC_WD-1:0] reg_addr     =  {1'b0, per_addr[DEC_WD-2:0]};

// Register address decode

wire [DEC_SZ-1:0] reg_dec      = (BCSCTL1_D  &  {DEC_SZ{(reg_addr==(BCSCTL1 >>1))}}) |

                                 (BCSCTL2_D  &  {DEC_SZ{(reg_addr==(BCSCTL2 >>1))}});

// Read/Write probes

wire              reg_lo_write =  per_we[0] & reg_sel;

wire              reg_hi_write =  per_we[1] & reg_sel;

wire              reg_read     = ~|per_we   & reg_sel;

// Read/Write vectors

wire [DEC_SZ-1:0] reg_hi_wr    = reg_dec & {DEC_SZ{reg_hi_write}};

wire [DEC_SZ-1:0] reg_lo_wr    = reg_dec & {DEC_SZ{reg_lo_write}};

wire [DEC_SZ-1:0] reg_rd       = reg_dec & {DEC_SZ{reg_read}};

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

// 3) REGISTERS

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

// BCSCTL1 Register

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

reg  [7:0] bcsctl1;

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

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

always @ (posedge mclk or posedge puc_rst)

  if (puc_rst)          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] : reg_lo_wr[BCSCTL2];

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

always @ (posedge mclk or posedge puc_rst)

  if (puc_rst)          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]}})}  << (8 & {4{BCSCTL1[0]}});

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

wire [15:0] per_dout =  bcsctl1_rd   |

                        bcsctl2_rd;

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

// 5)  CLOCK GENERATION

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

// Synchronize CPU_EN signal

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

`ifdef SYNC_CPU_EN

omsp_sync_cell sync_cell_cpu_en (

    .data_out (cpu_en_s),

    .clk      (mclk),

    .data_in  (cpu_en),

    .rst      (por)

);

`else

   assign cpu_en_s = cpu_en;

`endif

// Synchronize LFXT_CLK & edge detection

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

wire lfxt_clk_s;

omsp_sync_cell sync_cell_lfxt_clk (

    .data_out (lfxt_clk_s),

    .clk      (mclk),

    .data_in  (lfxt_clk),

    .rst      (por)

);

reg  lfxt_clk_dly;

always @ (posedge mclk or posedge por)

  if (por) lfxt_clk_dly <=  1'b0;

  else     lfxt_clk_dly <=  lfxt_clk_s;

wire lfxt_clk_en = (lfxt_clk_s & ~lfxt_clk_dly) & ~(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_rst)

  if (puc_rst)  aclk_en <=  1'b0;

  else          aclk_en <=  aclk_en_nxt & cpu_en_s;

always @ (posedge mclk or posedge puc_rst)

  if (puc_rst)                                     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_rst)

  if (puc_rst)  smclk_en <=  1'b0;

  else          smclk_en <=  smclk_en_nxt & cpu_en_s;

always @ (posedge mclk or posedge puc_rst)

  if (puc_rst)                                  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_n;

wire      por_reset_a  =  !reset_n;

omsp_sync_cell sync_cell_por (

    .data_out (por_n),

    .clk      (mclk),

    .data_in  (1'b1),

    .rst      (por_reset_a)

);

wire   por = ~por_n;

// Generate main system reset

wire      puc_rst_comb = por | wdt_reset | dbg_cpu_reset;

reg       puc_rst;

always @(posedge mclk or posedge puc_rst_comb)

  if (puc_rst_comb) puc_rst  <=  1'b1;

  else              puc_rst  <=  1'b0;

// Generate debug unit reset

`ifdef DBG_EN

wire   dbg_rst_n;

  `ifdef SYNC_DBG_EN

     omsp_sync_cell sync_cell_dbg_en (

        .data_out (dbg_rst_n),

        .clk      (mclk),

        .data_in  (dbg_en),

        .rst      (por)

    );

  `else

assign dbg_rst_n = dbg_en;

  `endif

`else

wire   dbg_rst_n  = 1'b0;

`endif

wire   dbg_en_s   =  dbg_rst_n;

wire   dbg_rst    = ~dbg_rst_n;

endmodule // omsp_clock_module

`ifdef OMSP_NO_INCLUDE

`else

`include "openMSP430_undefines.v"

`endif