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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: 103 $
// $LastChangedBy: olivier.girard $
// $LastChangedDate: 2011-03-05 15:44:48 +0100 (Sat, 05 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_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