Subversion Repositories p16c5x

////////////////////////////////////////////////////////////////////////////////

//

//  Copyright 2008-2013 by Michael A. Morris, dba M. A. Morris & Associates

//

//  All rights reserved. The source code contained herein is publicly released

//  under the terms and conditions of the GNU Lesser Public License. No part of

//  this source code may be reproduced or transmitted in any form or by any

//  means, electronic or mechanical, including photocopying, recording, or any

//  information storage and retrieval system in violation of the license under

//  which the source code is released.

//

//  The source code contained herein is free; it may be redistributed and/or

//  modified in accordance with the terms of the GNU Lesser General Public

//  License as published by the Free Software Foundation; either version 2.1 of

//  the GNU Lesser General Public License, or any later version.

//

//  The source code contained herein is freely released WITHOUT ANY WARRANTY;

//  without even the implied warranty of MERCHANTABILITY or FITNESS FOR A

//  PARTICULAR PURPOSE. (Refer to the GNU Lesser General Public License for

//  more details.)

//

//  A copy of the GNU Lesser General Public License should have been received

//  along with the source code contained herein; if not, a copy can be obtained

//  by writing to:

//

//  Free Software Foundation, Inc.

//  51 Franklin Street, Fifth Floor

//  Boston, MA  02110-1301 USA

//

//  Further, no use of this source code is permitted in any form or means

//  without inclusion of this banner prominently in any derived works.

//

//  Michael A. Morris

//  Huntsville, AL

//

////////////////////////////////////////////////////////////////////////////////

`timescale 1ns / 1ps

////////////////////////////////////////////////////////////////////////////////

// Company:         M. A. Morris & Associates

// Engineer:        Michael A. Morris

//

// Create Date:     11:30:15 01/13/2008

// Design Name:     PIC16C5x

// Module Name:     C:/ISEProjects/ISE10.1i/P16C5x/PIC16C5x_Top.v

// Project Name:    PIC16C5x

// Target Devices:  N/A

// Tool versions:   ISEWebPACK 10.1i SP3

//

// Description:

//

//  Module implements a pipelined PIC16C5x processor. The processor implements

//  all PIC16C5x instructions. The module is derived from the PIC16C5x.v module

//  and removes the tristate control, output, and input registers associated

//  with Ports A...C. These ports are replaced by decoded 6 WE and 3 RE and an

//  I/O data bus. Three WEs assert when the TRIS A, TRIS B, or TRIS C instruc-

//  tions are exectued. The remaining three WEs assert when a register file

//  operation writes to addresses 0x05-0x07, which represent writes to the out-

//  put registers of Ports A...C, respectively. The three REs assert when regis-

//  ter file operations read addresses 0x05-0x07, which represent reads from the

//  input registers of Ports A...C, respectively.

//

//  Note:   Read-Modify-Write operations to register file addresses 0x05-0x07

//          only assert the corresponding WEs. The external logic is expected to

//          multiplex the input registers onto the I/O Data Input (IO_DI) bus on

//          the basis of the addresses. The core reads IO_DI and writes out the

//          modified data on the I/O Data Output (IO_DO) bus. In the event that

//          the input registers are implemented as FIFOs, this approach prevents

//          the assertion of a read strobe to the FIFO, which would advance the

//          pointers and cause the loss of the data at the head of the FIFO.

//

// Dependencies:    None

//

// Revision:

//

//  1.00    13F15   MAM     Converted PIC16C5x.v. The conversion entails remov-

//                          ing I/O ports and adding external DI/DO data bus, 

//                          write and read enables for I/O port registers and

//                          input buffers. This will demonstrate how PIC16C5x

//                          can be modified to support more sophisticated I/O.

//

//  1.10    13F15   MAM     Pulled in the optimized instruction decoder from

//                          F16C5x.v. Also converted the ALU section into a

//                          separate module.

//

//  1.30    13F20   MAM     Added parameter to determine reset vector. Although

//                          a full 4k x 12 program memory is available, no stan-

//                          dard 12-bit instruction length PIC supports that

//                          amount of program memory. To use free PIC-compatible

//                          tools, the parameter can be set to a value in the

//                          range of the supported devices.

//

//  1.40    13G07   MAM     Corrected error with the test conditional pertaining

//                          to BTFSC/BTFSS instructions. Qualifier was using

//                          ALU_Op[1:0] instead of ALU_Op[7:6]. Under certain

//                          combinations, results were correct.

//

// Additional Comments:

//

////////////////////////////////////////////////////////////////////////////////

module P16C5x #(

    parameter pRstVector = 12'h7FF,         // Reset Vector Location (PIC16F59)

    parameter pWDT_Size  = 20,              // Use 20 for synth. and 10 for Sim.

    parameter pRAMA_Init = "Src/RAMA.coe",  // RAM A initial value file ( 8x8)

    parameter pRAMB_Init = "Src/RAMB.coe"   // RAM B initial value file (64x8)

)(

    input   POR,                // In  - System Power-On Reset

    input   Clk,                // In  - System Clock

    input   ClkEn,              // In  - Processor Clock Enable

    input   MCLR,               // In  - Master Clear Input

    input   T0CKI,              // In  - Timer 0 Clock Input

    input   WDTE,               // In  - Watchdog Timer Enable

    output  reg [11:0] PC,      // Out - Program Counter

    input   [11:0] ROM,         // In  - Instruction Data Input

    output  WE_TRISA, WE_TRISB, WE_TRISC,   // Out - Tristate Register X WE

    output  WE_PORTA, WE_PORTB, WE_PORTC,   // Out - Port X Output Register

    output  RE_PORTA, RE_PORTB, RE_PORTC,   // In  - Port X Input Register

    output  [7:0] IO_DO,        // Out - I/O Bus Data Output

    input   [7:0] IO_DI,        // In  - I/O Bus Data Input

//

//  Debug Outputs

//

    output  reg Rst,            // Out - Internal Core Reset

    output  reg [5:0] OPTION,   // Out - Processor Configuration Register Output

    output  reg [11:0] IR,      // Out - Internal Instruction Register

    output  [ 9:0] dIR,         // Out - Pipeline Register (Non-ALU Instruct.)

    output  [11:0] ALU_Op,      // Out - Pipeline Register (ALU Instructions)

    output  [ 8:0] KI,          // Out - Pipeline Register (Literal)

    output  Err,                // Out - Instruction Decode Error Output

    output  reg Skip,           // Out - Skip Next Instruction

    output  reg [11:0] TOS,     // Out - Top-Of-Stack Register Output

    output  reg [11:0] NOS,     // Out - Next-On-Stack Register Output

    output  [7:0] W,            // Out - Working Register Output

    output  [7:0] FA,           // Out - File Address Output

    output  [7:0] DO,           // Out - File Data Input/ALU Data Output

    output  [7:0] DI,           // Out - File Data Output/ALU Data Input

    output  reg [7:0] TMR0,     // Out - Timer 0 Timer/Counter Output

    output  reg [7:0] FSR,      // Out - File Select Register Output

    output  [7:0] STATUS,       // Out - Processor Status Register Output

    output  T0CKI_Pls,          // Out - Timer 0 Clock Edge Pulse Output

    output  reg WDTClr,         // Out - Watchdog Timer Clear Output

    output  reg [pWDT_Size-1:0] WDT, // Out - Watchdog Timer

    output  reg WDT_TC,

    output  WDT_TO,             // Out - Watchdog Timer Timeout Output

    output  reg [7:0] PSCntr,   // Out - Prescaler Counter Output

    output  PSC_Pls             // Out - Prescaler Count Pulse Output

);

////////////////////////////////////////////////////////////////////////////////

//

//  Local Parameter Declarations

//

//  Special Function Register Addresses

localparam pINDF   = 5'b0_0000;     // Indirect Rd/Wr -- Address in FSR (0x04)

localparam pTMR0   = 5'b0_0001;     // Timer 0

localparam pPCL    = 5'b0_0010;     // Lower 8-bits of PC

localparam pSTATUS = 5'b0_0011;     // Status Register

localparam pFSR    = 5'b0_0100;     // File Select Register - Extended RAM ptr

localparam pPORTA  = 5'b0_0101;     // Port A: Tristate, Output, Input Registers

localparam pPORTB  = 5'b0_0110;     // Port B: Tristate, Output, Input Registers

localparam pPORTC  = 5'b0_0111;     // Port C: Tristate, Output, Input Registers

////////////////////////////////////////////////////////////////////////////////

//

//  Module Level Declarations

//

wire    Rst_M16C5x;         // Internal Core Reset (asynchronous)

wire    CE;                 // Internal Clock Enable: CE <= ClkEn & ~PD;

reg     [2:0] PA;           // PC Load Register PC[11:9] = PA[2:0]

reg     [7:0] SFR;          // Special Function Registers Data Output

wire    Rst_TO;             // Rst TO FF signal

reg     TO;                 // Time Out FF (STATUS Register)

wire    Rst_PD;             // Rst Power Down FF signal

reg     PD;                 // Power Down FF (STATUS Register)

reg     PwrDn;              // Power Down FF

// RAM Address: FA[4] ? {2'b0, FA[3:0]} : {FSR[6:5], FA[3:0]}

wire    [5:0] Addrs;

reg     [7:0] RAMA[ 7:0];   // RAM Block 0    = 0x08 - 0x0F      (Non-Banked)

reg     [7:0] RAMB[63:0];   // RAM Block 1..8 = @{FSR[6:5],FSR[3:0]} (Banked)

wire    T0CS;               // Timer 0 Clock Source Select

wire    T0SE;               // Timer 0 Source Edge

wire    PSA;                // Prescaler Assignment

wire    [2:0] PS;           // Prescaler Counter Output Bit Select

reg     [2:0] dT0CKI;       // Ext T0CKI Synchronized RE/RE FF chain

reg     PSC_Out;            // Synchronous Prescaler TC register

reg     [1:0] dPSC_Out;     // Rising Edge Detector for Prescaler output

wire    GOTO, CALL, RETLW;  // Signals for Decoded Instruction Register

wire    WE_SLEEP, WE_WDTCLR;

wire    WE_OPTION;

wire    WE_TMR0;            // Write Enable Signals Decoded from FA[4:0]

wire    WE_PCL;

wire    WE_STATUS;

wire    WE_FSR;

wire    WE_PSW;             // Write Enable for STATUS[2:0]: {Z, DC, C}

////////////////////////////////////////////////////////////////////////////////

//

//  ALU Declarations

//

wire    C, DC, Z;       // ALU Status Outputs

wire    Z_Tst, g;       // Zero and Bit Test Condition Code 

//

////////////////////////////////////////////////////////////////////////////////

////////////////////////////////////////////////////////////////////////////////

//

//  Top Level Implementation

//

assign CE = ClkEn & ~PwrDn;         // Internal Clock Enable, refer to comments

assign Rst_M16C5x = (POR | MCLR | WDT_TO);      // Internal Processor Reset

always @(posedge Clk or posedge Rst_M16C5x)

begin

    if(Rst_M16C5x)

        Rst <= #1 ~0;

    else if(CE)

        Rst <= #1  0;

end

//  Capture Program ROM input into Instruction Register (IR)

always @(posedge Clk)

begin

    if(Rst)

        IR <= #1 0;

    else if(CE)

        IR <= #1 ROM;

end

//  Instantiate Optimized Instruction Decoder - ROMs used to speed decode

P16C5x_IDec IDEC (

                .Rst(Rst),

                .Clk(Clk),

                .CE(CE),

                .DI(ROM),

                .Skip(Skip),

                .dIR(dIR),

                .ALU_Op(ALU_Op),

                .KI(KI),

                .Err(Err)

            );

//  Instantiate ALU module

P16C5x_ALU  ALU (

                .Rst(Rst),

                .Clk(Clk),

                .CE(CE),

                .ALU_Op(ALU_Op),

                .DI(DI),

                .KI(KI[7:0]),

                .WE_PSW(WE_PSW),

                .DO(DO),

                .Z_Tst(Z_Tst),

                .g(g),

                .W(W),

                .Z(Z),

                .DC(DC),

                .C(C)

            );

////////////////////////////////////////////////////////////////////////////////

////////////////////////////////////////////////////////////////////////////////

//

//  Microprocessor Core Implementation

//

//  Pipeline Instruction Register Assignments

assign GOTO      = dIR[0];

assign CALL      = dIR[1];

assign RETLW     = dIR[2];

assign WE_SLEEP  = dIR[3];

assign WE_WDTCLR = dIR[4];

assign WE_TRISA  = dIR[5];

assign WE_TRISB  = dIR[6];

assign WE_TRISC  = dIR[7];

assign WE_OPTION = dIR[8];

assign LITERAL   = dIR[9];      // Added to support WE/RE PortX external I/F

//  Skip Logic

assign Tst = ALU_Op[8];

always @(*)

begin

    Skip <= WE_SLEEP | WE_PCL

            | ((Tst) ? ((ALU_Op[7] & ALU_Op[6]) ? g    : Z_Tst)

                     : ((GOTO | CALL | RETLW)   ? 1'b1 : 1'b0 ));

end

//  File Register Address Multiplexer

assign INDF = ALU_Op[10];

assign FA   = ((INDF) ? FSR

                      : ((KI[4]) ? {FSR[6:5], KI[4:0]}

                                 : {    2'b0, KI[4:0]}));

//  File Register Write Enable

assign WE_F = ALU_Op[11];

//  Special Function Register Write Enables

assign WE_TMR0   =  WE_F & (FA[4:0] == pTMR0);

assign WE_PCL    =  WE_F & (FA[4:0] == pPCL);

assign WE_STATUS =  WE_F & (FA[4:0] == pSTATUS);

assign WE_FSR    =  WE_F & (FA[4:0] == pFSR);

//

//  I/O Ports moved to an external implementation

//      WE_PortX asserts for an FA address match when LITERAL not asserted and a

//          WE_F is asserted.

//      RE_PortX asserts for an FA address match whn LITERAL not asserted, WE_F

//          is not asserted, and WE_TrisX not asserted. Tris X has the same FA

//          field. Tristate control for port A is instruction 0x005, and FA is

//          the least significant 5 bits of the instruction. FA of 0x05 is the

//          file address of Port A. (The same applies for Tris B and Tris C.)

//

assign WE_PORTA  =  WE_F & (FA[4:0] == pPORTA) & ~LITERAL;

assign WE_PORTB  =  WE_F & (FA[4:0] == pPORTB) & ~LITERAL;

assign WE_PORTC  =  WE_F & (FA[4:0] == pPORTC) & ~LITERAL;

//

assign RE_PORTA  = ~WE_F & (FA[4:0] == pPORTA) & ~LITERAL & ~WE_TRISA;

assign RE_PORTB  = ~WE_F & (FA[4:0] == pPORTB) & ~LITERAL & ~WE_TRISB;

assign RE_PORTC  = ~WE_F & (FA[4:0] == pPORTC) & ~LITERAL & ~WE_TRISC;

//  Assign Write Enable for STATUS register Processor Status Word (PSW) bits

//      Allow write to the STATUS[2:0] bits, {Z, DC, C}, only for instructions

//      MOVWF, BCF, BSF, and SWAPF. Exclude instructions DECFSZ and INCFSZ.

assign WE_PSW = WE_STATUS & (ALU_Op[5:4] == 2'b00) & (ALU_Op[8] == 1'b0);

////////////////////////////////////////////////////////////////////////////////

//

// Program Counter Implementation

//

//  On CALL or MOVWF PCL (direct or indirect), load PCL from the ALU output

//  and the upper bits with {PA, 0}, i.e. PC[8] = 0.

//

assign Ld_PCL = CALL | WE_PCL;

always @(posedge Clk)

begin

    if(Rst)

        PC <= #1 pRstVector;    // Set PC to Reset Vector on Rst or WDT Timeout

    else if(CE)

        PC <= #1 (GOTO ? {PA, KI}

                       : (Ld_PCL ? {PA, 1'b0, DO}

                                 : (RETLW ? TOS : PC + 1)));

end

//  Stack Implementation (2 Level Stack)

always @(posedge Clk)

begin

    if(POR)

        TOS <= #1 pRstVector;       // Set TOS on Rst or WDT Timeout

    else if(CE)

        TOS <= #1 (CALL ? PC : (RETLW ? NOS : TOS));

end

always @(posedge Clk)

begin

    if(POR)

        NOS <= #1 pRstVector;       // Set NOS on Rst or WDT Timeout

    else if(CE)

        NOS <= #1 (CALL ? TOS : NOS);

end

////////////////////////////////////////////////////////////////////////////////

//

//  Port Configuration and Option Registers

always @(posedge Clk)

begin

    if(POR)

        OPTION <= #1 8'b0011_1111;

    else if(CE)

        OPTION <= #1 ((WE_OPTION) ? W : OPTION);

end

////////////////////////////////////////////////////////////////////////////////

//

//  CLRWDT Strobe Pulse Generator

always @(posedge Clk)

begin

    if(Rst)

        WDTClr <= #1 0;

    else

        WDTClr <= #1 (WE_WDTCLR | WE_SLEEP) & ~PwrDn;

end

////////////////////////////////////////////////////////////////////////////////

//

//  TO (Time Out) STATUS Register Bit

assign Rst_TO = (POR | (MCLR & PD) | WE_WDTCLR);

always @(posedge Clk)

begin

    if(Rst_TO)

        TO <= #1  0;

    else if(WDT_TO)

        TO <= #1 ~0;

end

////////////////////////////////////////////////////////////////////////////////

//

//  PD (Power Down) STATUS Register Bit - Sleep Mode

assign Rst_PD = POR | (WE_WDTCLR & ~PwrDn);

always @(posedge Clk)

begin

    if(Rst_PD)

        PD <= #1 0;

    else if(CE)

        PD <= #1 ((WE_SLEEP) ? 1'b1 : PD);

end

//  PwrDn - Sleep Mode Control FF: Set by SLEEP instruction, cleared by Rst

//          Differs from PD in that it is not readable and does not maintain

//          its state through Reset. Gates CE to rest of the processor.

always @(posedge Clk)

begin

    if(Rst)

        PwrDn <= #1 0;

    else if(ClkEn)

        PwrDn <= #1 ((WE_SLEEP) ? 1'b1 : PwrDn);

end

////////////////////////////////////////////////////////////////////////////////

//

//  File Register RAM

assign Addrs = {FA[6:5], FA[3:0]};

//  RAM A - 16 Word Distributed RAM

assign WE_RAMA = WE_F & ~FA[4] & FA[3];

initial

  $readmemh(pRAMA_Init, RAMA, 0, 7);

always @(posedge Clk)

begin

    if(CE)

        if(WE_RAMA)

            RAMA[Addrs[2:0]] <= #1 DO;

end

//  RAM B - 64 Word Distributed RAM

assign WE_RAMB = WE_F & FA[4];

initial

  $readmemh(pRAMB_Init, RAMB, 0, 63);

always @(posedge Clk)

begin

    if(CE)

        if(WE_RAMB)

            RAMB[Addrs] <= #1 DO;

end

////////////////////////////////////////////////////////////////////////////////

//

// Special Function Registers

always @(posedge Clk)

begin

    if(POR)

        PA  <= #1 0;

    else if(CE)

        PA  <= #1 ((WE_STATUS) ? DO[7:5] : PA);

end

always @(posedge Clk)

begin

    if(POR)

        FSR <= #1 0;

    else if(CE)

        FSR <= #1 ((WE_FSR) ? DO : FSR);

end

//  Generate STATUS Register

assign STATUS = {PA, ~TO, ~PD, Z, DC, C};

//  Special Function Register (SFR) Multiplexers

always @(*)

begin

    case(FA[2:0])

        3'b000 :  SFR <= 0;

        3'b001 :  SFR <= TMR0;

        3'b010 :  SFR <= PC[7:0];

        3'b011 :  SFR <= STATUS;

        3'b100 :  SFR <= FSR;

        3'b101 :  SFR <= IO_DI;

        3'b110 :  SFR <= IO_DI;

        3'b111 :  SFR <= IO_DI;

    endcase

end

//  File Data Output Multiplexer

assign DI = (FA[4] ? RAMB[Addrs] : (FA[3] ? RAMA[Addrs[2:0]] : SFR));

//  IO Data Output Multiplexer

assign IO_DO = ((|{WE_TRISA, WE_TRISB, WE_TRISC}) ? W : DO);

////////////////////////////////////////////////////////////////////////////////

////////////////////////////////////////////////////////////////////////////////

//

//  Watchdog Timer and Timer0 Implementation- see Figure 8-6

//

//  OPTION Register Assignments

assign T0CS = OPTION[5];     // Timer0 Clock Source:   1 - T0CKI,  0 - Clk

assign T0SE = OPTION[4];     // Timer0 Source Edge:    1 - FE,     0 - RE

assign PSA  = OPTION[3];     // Pre-Scaler Assignment: 1 - WDT,    0 - Timer0

assign PS   = OPTION[2:0];   // Pre-Scaler Count: Timer0 - 2^(PS+1), WDT - 2^PS

// WDT - Watchdog Timer

assign WDT_Rst = Rst | WDTClr;

always @(posedge Clk)

begin

    if(WDT_Rst)

        WDT <= #1 0;

    else if(WDTE)

        WDT <= #1 WDT + 1;

end

//  WDT synchronous TC FF

always @(posedge Clk)

begin

    if(WDT_Rst)

        WDT_TC <= #1 0;

    else

        WDT_TC <= #1 &WDT;

end

// WDT Timeout multiplexer

assign WDT_TO = (PSA ? PSC_Pls : WDT_TC);

////////////////////////////////////////////////////////////////////////////////

//

//  T0CKI RE/FE Pulse Generator (on Input rather than after PSCntr)

//

//      Device implements an XOR on T0CKI and a clock multiplexer for the

//      Prescaler since it has two clock asynchronous clock sources: the WDT

//      or the external T0CKI (Timer0 Clock Input). Instead of this type of

//      gated clock ripple counter implementation of the Prescaler, a fully

//      synchronous implementation has been selected. Thus, the T0CKI must be

//      synchronized and the falling or rising edge detected as determined by

//      the T0CS bit in the OPTION register. Similarly, the WDT is implemented

//      using the processor clock, which means that the WDT TC pulse is in the

//      same clock domain as the rest of the logic.

//

always @(posedge Clk)

begin

    if(Rst)

        dT0CKI <= #1 0;

    else begin

        dT0CKI[0] <= #1 T0CKI;                              // Synch FF #1

        dT0CKI[1] <= #1 dT0CKI[0];                          // Synch FF #2

        dT0CKI[2] <= #1 (T0SE ? (dT0CKI[1] & ~dT0CKI[0])    // Falling Edge

                              : (dT0CKI[0] & ~dT0CKI[1]));  // Rising Edge

    end

end

assign T0CKI_Pls = dT0CKI[2]; // T0CKI Pulse out, either FE/RE

//  Tmr0 Clock Source Multiplexer

assign Tmr0_CS = (T0CS ? T0CKI_Pls : CE);

////////////////////////////////////////////////////////////////////////////////

//

// Pre-Scaler Counter

assign Rst_PSC   = (PSA ? WDTClr : WE_TMR0) | Rst;

assign CE_PSCntr = (PSA ? WDT_TC : Tmr0_CS);

always @(posedge Clk)

begin

    if(Rst_PSC)

        PSCntr <= #1 0;

    else if(CE_PSCntr)

        PSCntr <= #1 PSCntr + 1;

end

//  Prescaler Counter Output Multiplexer

always @(*)

begin

    case (PS)

        3'b000 : PSC_Out <= PSCntr[0];

        3'b001 : PSC_Out <= PSCntr[1];

        3'b010 : PSC_Out <= PSCntr[2];

        3'b011 : PSC_Out <= PSCntr[3];

        3'b100 : PSC_Out <= PSCntr[4];

        3'b101 : PSC_Out <= PSCntr[5];

        3'b110 : PSC_Out <= PSCntr[6];

        3'b111 : PSC_Out <= PSCntr[7];

    endcase

end