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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_sfr.v

// 

// *Module Description:

//                       Processor Special function register

//

// *Author(s):

//              - Olivier Girard,    olgirard@gmail.com

//

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

// $Rev: 85 $

// $LastChangedBy: olivier.girard $

// $LastChangedDate: 2011-01-28 22:05:37 +0100 (Fri, 28 Jan 2011) $

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

`include "timescale.v"

`include "openMSP430_defines.v"

module  omsp_sfr (

// OUTPUTs

    nmie,                         // Non-maskable interrupt enable

    per_dout,                     // Peripheral data output

    wdt_irq,                      // Watchdog-timer interrupt

    wdt_reset,                    // Watchdog-timer reset

    wdtie,                        // Watchdog-timer interrupt enable

// INPUTs

    mclk,                         // Main system clock

    nmi_acc,                      // Non-Maskable interrupt request accepted

    per_addr,                     // Peripheral address

    per_din,                      // Peripheral data input

    per_en,                       // Peripheral enable (high active)

    per_wen,                      // Peripheral write enable (high active)

    por,                          // Power-on reset

    puc,                          // Main system reset

    wdtifg_clr,                   // Clear Watchdog-timer interrupt flag

    wdtifg_set,                   // Set Watchdog-timer interrupt flag

    wdtpw_error,                  // Watchdog-timer password error

    wdttmsel                      // Watchdog-timer mode select

);

// OUTPUTs

//=========

output              nmie;         // Non-maskable interrupt enable

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

output              wdt_irq;      // Watchdog-timer interrupt

output              wdt_reset;    // Watchdog-timer reset

output              wdtie;        // Watchdog-timer interrupt enable

// INPUTs

//=========

input               mclk;         // Main system clock

input               nmi_acc;      // Non-Maskable interrupt request accepted

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_wen;      // Peripheral write enable (high active)

input               por;          // Power-on reset

input               puc;          // Main system reset

input               wdtifg_clr;   // Clear Watchdog-timer interrupt flag

input               wdtifg_set;   // Set Watchdog-timer interrupt flag

input               wdtpw_error;  // Watchdog-timer password error

input               wdttmsel;     // Watchdog-timer mode select

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

// 1)  PARAMETER DECLARATION

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

// Register addresses

parameter           IE1        = 9'h000;

parameter           IFG1       = 9'h002;

// Register one-hot decoder

parameter           IE1_D      = (256'h1 << (IE1  /2));

parameter           IFG1_D     = (256'h1 << (IFG1 /2));

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

// 2)  REGISTER DECODER

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

// Register address decode

reg  [255:0]  reg_dec;

always @(per_addr)

  case (per_addr)

    (IE1  /2):     reg_dec  =  IE1_D;

    (IFG1 /2):     reg_dec  =  IFG1_D;

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

  endcase

// Read/Write probes

wire         reg_lo_write =  per_wen[0] & per_en;

wire         reg_hi_write =  per_wen[1] & per_en;

wire         reg_read     = ~|per_wen   & 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

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

// IE1 Register

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

wire [7:0] ie1;

wire       ie1_wr  = IE1[0] ? reg_hi_wr[IE1/2] : reg_lo_wr[IE1/2];

wire [7:0] ie1_nxt = IE1[0] ? per_din[15:8]    : per_din[7:0];

reg        nmie;

always @ (posedge mclk or posedge puc)

  if (puc)          nmie  <=  1'b0;

  else if (nmi_acc) nmie  <=  1'b0;

  else if (ie1_wr)  nmie  <=  ie1_nxt[4];

reg        wdtie;

always @ (posedge mclk or posedge puc)

  if (puc)           wdtie <=  1'b0;

  else if (ie1_wr)   wdtie <=  ie1_nxt[0];

assign  ie1 = {3'b000, nmie, 3'b000, wdtie};

// IFG1 Register

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

wire [7:0] ifg1;

wire       ifg1_wr  = IFG1[0] ? reg_hi_wr[IFG1/2] : reg_lo_wr[IFG1/2];

wire [7:0] ifg1_nxt = IFG1[0] ? per_din[15:8]     : per_din[7:0];

reg        nmiifg;

always @ (posedge mclk or posedge puc)

  if (puc)           nmiifg <=  1'b0;

  else if (nmi_acc)  nmiifg <=  1'b1;

  else if (ifg1_wr)  nmiifg <=  ifg1_nxt[4];

reg        wdtifg;

always @ (posedge mclk or posedge por)

  if (por)                        wdtifg <=  1'b0;

  else if (wdtifg_set)            wdtifg <=  1'b1;

  else if (wdttmsel & wdtifg_clr) wdtifg <=  1'b0;

  else if (ifg1_wr)               wdtifg <=  ifg1_nxt[0];

assign  ifg1 = {3'b000, nmiifg, 3'b000, wdtifg};

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

// 4) DATA OUTPUT GENERATION

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

// Data output mux

wire [15:0] ie1_rd   = {8'h00, (ie1  & {8{reg_rd[IE1/2]}})}  << (8 & {4{IE1[0]}});

wire [15:0] ifg1_rd  = {8'h00, (ifg1 & {8{reg_rd[IFG1/2]}})} << (8 & {4{IFG1[0]}});

wire [15:0] per_dout =  ie1_rd   |

                        ifg1_rd;

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

// 5)  WATCHDOG INTERRUPT & RESET

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

// Watchdog interrupt generation

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

wire    wdt_irq      = wdttmsel & wdtifg & wdtie;

// Watchdog reset generation

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

reg     wdt_reset;

always @ (posedge mclk or posedge por)

  if (por) wdt_reset <= 1'b0;

  else     wdt_reset <= wdtpw_error | (wdtifg_set & ~wdttmsel);

endmodule // omsp_sfr

`include "openMSP430_undefines.v"