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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_register_file.v

// 

// *Module Description:

//                       openMSP430 Register files

//

// *Author(s):

//              - Olivier Girard,    olgirard@gmail.com

//

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

// $Rev: 34 $

// $LastChangedBy: olivier.girard $

// $LastChangedDate: 2009-12-29 20:10:34 +0100 (Di, 29 Dez 2009) $

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

`include "timescale.v"

`include "openMSP430_defines.v"

module  omsp_register_file (

// OUTPUTs

    cpuoff,                       // Turns off the CPU

    gie,                          // General interrupt enable

    oscoff,                       // Turns off LFXT1 clock input

    pc_sw,                        // Program counter software value

    pc_sw_wr,                     // Program counter software write

    reg_dest,                     // Selected register destination content

    reg_src,                      // Selected register source content

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

    status,                       // R2 Status {V,N,Z,C}

// INPUTs

    alu_stat,                     // ALU Status {V,N,Z,C}

    alu_stat_wr,                  // ALU Status write {V,N,Z,C}

    inst_bw,                      // Decoded Inst: byte width

    inst_dest,                    // Register destination selection

    inst_src,                     // Register source selection

    mclk,                         // Main system clock

    pc,                           // Program counter

    puc,                          // Main system reset

    reg_dest_val,                 // Selected register destination value

    reg_dest_wr,                  // Write selected register destination

    reg_pc_call,                  // Trigger PC update for a CALL instruction

    reg_sp_val,                   // Stack Pointer next value

    reg_sp_wr,                    // Stack Pointer write

    reg_sr_wr,                    // Status register update for RETI instruction

    reg_sr_clr,                   // Status register clear for interrupts

    reg_incr                      // Increment source register

);

// OUTPUTs

//=========

output              cpuoff;       // Turns off the CPU

output              gie;          // General interrupt enable

output              oscoff;       // Turns off LFXT1 clock input

output       [15:0] pc_sw;        // Program counter software value

output              pc_sw_wr;     // Program counter software write

output       [15:0] reg_dest;     // Selected register destination content

output       [15:0] reg_src;      // Selected register source content

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

output        [3:0] status;       // R2 Status {V,N,Z,C}

// INPUTs

//=========

input         [3:0] alu_stat;     // ALU Status {V,N,Z,C}

input         [3:0] alu_stat_wr;  // ALU Status write {V,N,Z,C}

input               inst_bw;      // Decoded Inst: byte width

input        [15:0] inst_dest;    // Register destination selection

input        [15:0] inst_src;     // Register source selection

input               mclk;         // Main system clock

input        [15:0] pc;           // Program counter

input               puc;          // Main system reset

input        [15:0] reg_dest_val; // Selected register destination value

input               reg_dest_wr;  // Write selected register destination

input               reg_pc_call;  // Trigger PC update for a CALL instruction

input        [15:0] reg_sp_val;   // Stack Pointer next value

input               reg_sp_wr;    // Stack Pointer write

input               reg_sr_wr;    // Status register update for RETI instruction

input               reg_sr_clr;   // Status register clear for interrupts

input               reg_incr;     // Increment source register

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

// 1)  AUTOINCREMENT UNIT

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

wire [15:0] incr_op         = inst_bw ? 16'h0001 : 16'h0002;

wire [15:0] reg_incr_val    = reg_src+incr_op;

wire [15:0] reg_dest_val_in = inst_bw ? {8'h00,reg_dest_val[7:0]} : reg_dest_val;

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

// 2)  SPECIAL REGISTERS (R1/R2/R3)

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

// Source input selection mask (for interrupt support)

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

wire [15:0] inst_src_in = reg_sr_clr ? 16'h0004 : inst_src;

// R0: Program counter

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

wire [15:0] r0       = pc;

wire [15:0] pc_sw    = reg_dest_val_in;

wire        pc_sw_wr = (inst_dest[0] & reg_dest_wr) | reg_pc_call;

// R1: Stack pointer

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

reg [15:0] r1;

wire       r1_wr  = inst_dest[1] & reg_dest_wr;

wire       r1_inc = inst_src_in[1]  & reg_incr;

always @(posedge mclk or posedge puc)

  if (puc)            r1 <= 16'h0000;

  else if (r1_wr)     r1 <= reg_dest_val_in & 16'hfffe;

  else if (reg_sp_wr) r1 <= reg_sp_val      & 16'hfffe;

  else if (r1_inc)    r1 <= reg_incr_val    & 16'hfffe;

// R2: Status register

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

reg  [15:0] r2;

wire        r2_wr  = (inst_dest[2] & reg_dest_wr) | reg_sr_wr;

wire        r2_c   = alu_stat_wr[0] ? alu_stat[0]       :

                     r2_wr          ? reg_dest_val_in[0]   : r2[0]; // C

wire        r2_z   = alu_stat_wr[1] ? alu_stat[1]       :

                     r2_wr          ? reg_dest_val_in[1]   : r2[1]; // Z

wire        r2_n   = alu_stat_wr[2] ? alu_stat[2]       :

                     r2_wr          ? reg_dest_val_in[2]   : r2[2]; // N

wire  [7:3] r2_nxt = r2_wr          ? reg_dest_val_in[7:3] : r2[7:3];

wire        r2_v   = alu_stat_wr[3] ? alu_stat[3]       :

                     r2_wr          ? reg_dest_val_in[8]   : r2[8]; // V

always @(posedge mclk or posedge puc)

  if (puc)             r2 <= 16'h0000;

  else if (reg_sr_clr) r2 <= 16'h0000;

  else                 r2 <= {7'h00, r2_v, r2_nxt, r2_n, r2_z, r2_c};

assign status = {r2[8], r2[2:0]};

assign gie    =  r2[3];

assign cpuoff =  r2[4] | (r2_nxt[4] & r2_wr);

assign oscoff =  r2[5];

assign scg1   =  r2[7];

// R3: Constant generator

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

reg [15:0] r3;

wire       r3_wr  = inst_dest[3] & reg_dest_wr;

wire       r3_inc = inst_src_in[3]  & reg_incr;

always @(posedge mclk or posedge puc)

  if (puc)         r3 <= 16'h0000;

  else if (r3_wr)  r3 <= reg_dest_val_in;

  else if (r3_inc) r3 <= reg_incr_val;

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

// 4)  GENERAL PURPOSE REGISTERS (R4...R15)

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

// R4

reg [15:0] r4;

wire       r4_wr  = inst_dest[4] & reg_dest_wr;

wire       r4_inc = inst_src_in[4]  & reg_incr;

always @(posedge mclk or posedge puc)

  if (puc)          r4  <= 16'h0000;

  else if (r4_wr)   r4  <= reg_dest_val_in;

  else if (r4_inc)  r4  <= reg_incr_val;

// R5

reg [15:0] r5;

wire       r5_wr  = inst_dest[5] & reg_dest_wr;

wire       r5_inc = inst_src_in[5]  & reg_incr;

always @(posedge mclk or posedge puc)

  if (puc)          r5  <= 16'h0000;

  else if (r5_wr)   r5  <= reg_dest_val_in;

  else if (r5_inc)  r5  <= reg_incr_val;

// R6

reg [15:0] r6;

wire       r6_wr  = inst_dest[6] & reg_dest_wr;

wire       r6_inc = inst_src_in[6]  & reg_incr;

always @(posedge mclk or posedge puc)

  if (puc)          r6  <= 16'h0000;

  else if (r6_wr)   r6  <= reg_dest_val_in;

  else if (r6_inc)  r6  <= reg_incr_val;

// R7

reg [15:0] r7;

wire       r7_wr  = inst_dest[7] & reg_dest_wr;

wire       r7_inc = inst_src_in[7]  & reg_incr;

always @(posedge mclk or posedge puc)

  if (puc)          r7  <= 16'h0000;

  else if (r7_wr)   r7  <= reg_dest_val_in;

  else if (r7_inc)  r7  <= reg_incr_val;

// R8

reg [15:0] r8;

wire       r8_wr  = inst_dest[8] & reg_dest_wr;

wire       r8_inc = inst_src_in[8]  & reg_incr;

always @(posedge mclk or posedge puc)

  if (puc)          r8  <= 16'h0000;

  else if (r8_wr)   r8  <= reg_dest_val_in;

  else if (r8_inc)  r8  <= reg_incr_val;

// R9

reg [15:0] r9;

wire       r9_wr  = inst_dest[9] & reg_dest_wr;

wire       r9_inc = inst_src_in[9]  & reg_incr;

always @(posedge mclk or posedge puc)

  if (puc)          r9  <= 16'h0000;

  else if (r9_wr)   r9  <= reg_dest_val_in;

  else if (r9_inc)  r9  <= reg_incr_val;

// R10

reg [15:0] r10;

wire       r10_wr  = inst_dest[10] & reg_dest_wr;

wire       r10_inc = inst_src_in[10]  & reg_incr;

always @(posedge mclk or posedge puc)

  if (puc)          r10 <= 16'h0000;

  else if (r10_wr)  r10 <= reg_dest_val_in;

  else if (r10_inc) r10 <= reg_incr_val;

// R11

reg [15:0] r11;

wire       r11_wr  = inst_dest[11] & reg_dest_wr;

wire       r11_inc = inst_src_in[11]  & reg_incr;

always @(posedge mclk or posedge puc)

  if (puc)          r11 <= 16'h0000;

  else if (r11_wr)  r11 <= reg_dest_val_in;

  else if (r11_inc) r11 <= reg_incr_val;

// R12

reg [15:0] r12;

wire       r12_wr  = inst_dest[12] & reg_dest_wr;

wire       r12_inc = inst_src_in[12]  & reg_incr;

always @(posedge mclk or posedge puc)

  if (puc)          r12 <= 16'h0000;

  else if (r12_wr)  r12 <= reg_dest_val_in;

  else if (r12_inc) r12 <= reg_incr_val;

// R13

reg [15:0] r13;

wire       r13_wr  = inst_dest[13] & reg_dest_wr;

wire       r13_inc = inst_src_in[13]  & reg_incr;

always @(posedge mclk or posedge puc)

  if (puc)          r13 <= 16'h0000;

  else if (r13_wr)  r13 <= reg_dest_val_in;

  else if (r13_inc) r13 <= reg_incr_val;

// R14

reg [15:0] r14;

wire       r14_wr  = inst_dest[14] & reg_dest_wr;

wire       r14_inc = inst_src_in[14]  & reg_incr;

always @(posedge mclk or posedge puc)

  if (puc)          r14 <= 16'h0000;

  else if (r14_wr)  r14 <= reg_dest_val_in;

  else if (r14_inc) r14 <= reg_incr_val;

// R15

reg [15:0] r15;

wire       r15_wr  = inst_dest[15] & reg_dest_wr;

wire       r15_inc = inst_src_in[15]  & reg_incr;

always @(posedge mclk or posedge puc)

  if (puc)          r15 <= 16'h0000;

  else if (r15_wr)  r15 <= reg_dest_val_in;

  else if (r15_inc) r15 <= reg_incr_val;

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

// 5)  READ MUX

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

assign reg_src  = (r0      & {16{inst_src_in[0]}})   |

                  (r1      & {16{inst_src_in[1]}})   |

                  (r2      & {16{inst_src_in[2]}})   |

                  (r3      & {16{inst_src_in[3]}})   |

                  (r4      & {16{inst_src_in[4]}})   |

                  (r5      & {16{inst_src_in[5]}})   |

                  (r6      & {16{inst_src_in[6]}})   |

                  (r7      & {16{inst_src_in[7]}})   |

                  (r8      & {16{inst_src_in[8]}})   |

                  (r9      & {16{inst_src_in[9]}})   |

                  (r10     & {16{inst_src_in[10]}})  |

                  (r11     & {16{inst_src_in[11]}})  |

                  (r12     & {16{inst_src_in[12]}})  |

                  (r13     & {16{inst_src_in[13]}})  |

                  (r14     & {16{inst_src_in[14]}})  |

                  (r15     & {16{inst_src_in[15]}});

assign reg_dest = (r0      & {16{inst_dest[0]}})  |

                  (r1      & {16{inst_dest[1]}})  |

                  (r2      & {16{inst_dest[2]}})  |

                  (r3      & {16{inst_dest[3]}})  |

                  (r4      & {16{inst_dest[4]}})  |

                  (r5      & {16{inst_dest[5]}})  |

                  (r6      & {16{inst_dest[6]}})  |

                  (r7      & {16{inst_dest[7]}})  |

                  (r8      & {16{inst_dest[8]}})  |

                  (r9      & {16{inst_dest[9]}})  |

                  (r10     & {16{inst_dest[10]}}) |

                  (r11     & {16{inst_dest[11]}}) |

                  (r12     & {16{inst_dest[12]}}) |

                  (r13     & {16{inst_dest[13]}}) |

                  (r14     & {16{inst_dest[14]}}) |

                  (r15     & {16{inst_dest[15]}});

endmodule // omsp_register_file

`include "openMSP430_undefines.v"