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/*

 * Copyright (c) 2018, Marcelo Samsoniuk

 * All rights reserved.

 *

 * Redistribution and use in source and binary forms, with or without

 * modification, are permitted provided that the following conditions are met:

 *

 * * Redistributions of source code must retain the above copyright notice, this

 *   list of conditions and the following disclaimer.

 *

 * * Redistributions in binary form must reproduce the above copyright notice,

 *   this list of conditions and the following disclaimer in the documentation

 *   and/or other materials provided with the distribution.

 *

 * * Neither the name of the copyright holder nor the names of its

 *   contributors may be used to endorse or promote products derived from

 *   this software without specific prior written permission.

 *

 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"

 * AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE

 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE

 * DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE

 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL

 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR

 * SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER

 * CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,

 * OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE

 * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.

 */

`timescale 1ns / 1ps

// memory architecture

//

// TODO: fix the different memory architecture concepts:

// status:

// ICACHE: works without interrupt

// DCACHE: does not work!

// WAITSTATE: works

// 

//`define __ICACHE__              // instruction cache

//`define __DCACHE__              // data cache (bug: simulation only)

//`define __WAITSTATES__          // wait-state tests, no cache

// peripheral configuration

//

// UART speed is set in bits per second, typically 115200 bps:

`define __UARTSPEED__ 115200

// darkriscv/darksocv configuration

// 

// pipeline stages:

// 

// 2-stage version: core and memory in different clock edges result in less

// clock performance, but less losses when the program counter changes

// (pipeline flush = 1 clock).  Works like a 4-stage pipeline and remember

// the 68040 clock scheme, with instruction per clock = 1.  alternatively,

// it is possible work w/ 1 wait-state and 1 clock edge, but with a penalty

// in performance (instruction per clock = 0.5).

// 

// 3-stage version: core and memory in the same clock edge require one extra

// stage in the pipeline, but keep a good performance most of time

// (instruction per clock = 1).  of course, read operations require 1

// wait-state, which means sometimes the read performance is reduced.

`define __3STAGE__

// read-modify-write cycle:

//

// Generate RMW cycles when writing in the memory. This option basically 

// makes the read and write cycle symmetric and may work better in the cases

// when the 32-bit memory does not support separate write enables for 

// separate 16-bit and 8-bit words. Typically, the RMW cycle results in a

// decrease of 5% in the performance (not the clock, but the instruction

// pipeline eficiency) due to memory wait-states.

// Additional note: the RMW cycle is required for -O3 compilation!

//`define __RMW_CYCLE__

// muti-threading support:

//

// Decreases clock performance by 20% (80MHz), but enables two contexts

// (threads) in the core. The threads work in symmetrical way, which means

// that they will start with the same exactly core parameters (same initial

// PC, same initial SP, etc). The boot.s code is designed to handle this

// difference and set each thread to different applications.

// Notes: 

// a) threading is currently supported only in the 3-stage pipeline version.

// b) the old experimental "interrupt mode" was removed, which means that

//    the multi-thread mode does not make anything "visible" other than

//    increment the gpio register.

// c) the threading in the non interrupt mode just shares the core 50%/50%,

//    in a way that the single-thread performance is reduced.

//`define __THREADING__

// performance measurement:

//

// The performance measurement can be done in the simulation level by

// eabling the __PERFMETER__ define, in order to check how the clock cycles

// are used in the core. The report is displayed when the FINISH_REQ signal

// is actived by the UART.

`define __PERFMETER__

// mac instruction: 

// 

// The mac instruction is similar to other register to register

// instructions, but with a different opcode 7'h1111111.  the format is mac

// rd,r1,r2, but is not currently possible encode in asm, by this way it is

// available in licb as int mac(int rd, short r1, short r2).  Although it

// can be used to accelerate the mul/div operations, the mac operation is

// designed for DSP applications.  with some effort (low level machine

// code), it is possible peak 100MMAC/s @100MHz.

//`define __MAC16X16__

// RV32I vs RV32E:

//

// The difference between the RV32I and RV32E regarding the logic space is 

// minimal in typical applications with modern 5 or 6 input LUT based FPGAs, 

// but the RV32E is better with old 4 input LUT based FPGAs.

`define __RV32E__

// full harvard architecture:

// 

// When defined, enforses that the instruction and data buses are connected

// to fully separate memory banks.  Although the darkriscv always use

// harvard architecture in the core, with separate instruction and data

// buses, the logic levels outside the core can use different architectures

// and concepts, including von neumann, wich a single bus shared by

// instruction and data access, as well a mix between harvard and von

// neumann, which is possible in the case of dual-port blockrams, where is

// possible connect two separate buses in a single memory bank.  the main

// advantage of a single memory bank is that the .text and .data areas can

// be better allocated, but in this case is not possible protect the .text

// area as in the case of separate memory banks.

//`define __HARVARD__

// flexbuzz interface (experimental):

//

// A new data bus interface similar to a well known c*ldfire bus interface, in 

// a way that part of the bus routing is moved to the core, in a way that 

// is possible support different bus widths (8, 16 or 32 bit) and endians more 

// easily (the new interface is natively big-endian, but the endian can be adjusted

// in the bus interface dinamically). Similarly to the standard 32-bit interface, 

// the external logic must detect the RD/WR operation quick enough and assert HLT 

// in order to insert wait-states and perform the required multiplexing to fit 

// the DLEN operand size in the data bus width available.

`define __FLEXBUZZ__

// initial PC and SP

//

// it is possible program the initial PC and SP.  Typically, the PC is set

// to address 0, representing the start of ROM memory and the SP is set to

// the final of RAM memory.  In the linker, the start of ROM memory matches

// with the .text area, which is defined in the boot.c code and the start of

// RAM memory matches with the .data and other volatile data, in a way that

// the stack can be positioned in the top of RAM and does not match with the

// .data.

`define __RESETPC__ 32'd0

`define __RESETSP__ 32'd8192

// board definition:

// 

// The board is automatically defined in the xst/xise files via Makefile or

// ISE. Case it is not the case, please define you board name here:

//`define AVNET_MICROBOARD_LX9

//`define XILINX_AC701_A200

//`define QMTECH_SDRAM_LX16

// the following defines are automatically defined:

`ifdef __ICARUS__

    `define SIMULATION 1

`endif

`ifdef XILINX_ISIM

    `define SIMULATION 2

`endif

`ifdef MODEL_TECH

    `define SIMULATION 3

`endif

`ifdef XILINX_SIMULATOR

    `define SIMULATION 4

`endif

`ifdef AVNET_MICROBOARD_LX9

    `define BOARD_ID 1

    //`define BOARD_CK 100000000

    //`define BOARD_CK 66666666

    //`define BOARD_CK 40000000

    // example of DCM logic:

    `define BOARD_CK_REF 100000000

    `define BOARD_CK_MUL 2

    `ifdef __3STAGE__

        `define BOARD_CK_DIV 2 // 100MHz 

    `else

        `define BOARD_CK_DIV 4 // 50MHz

    `endif

`endif

`ifdef XILINX_AC701_A200

    `define BOARD_ID 2

    //`define BOARD_CK 90000000

    `define BOARD_CK_REF 90000000

    `define BOARD_CK_MUL 4

    `define BOARD_CK_DIV 2

`endif

`ifdef QMTECH_SDRAM_LX16

    `define BOARD_ID 3

    `define BOARD_CK_REF 50000000

    `define BOARD_CK_MUL 4

    `define BOARD_CK_DIV 2

    `define INVRES 1

`endif

`ifdef QMTECH_SPARTAN7_S15

    `define BOARD_ID 4

    `define BOARD_CK_REF 50000000

    `define BOARD_CK_MUL 20

    `define BOARD_CK_DIV 10

    `define XILINX7CLK 1

    `define VIVADO 1

    `define INVRES 1

`endif

`ifdef LATTICE_BREVIA2_XP2

    `define BOARD_ID 5

    `define BOARD_CK 50000000

    `define INVRES 1

`endif

`ifdef PISWORDS_RS485_LX9

    `define BOARD_ID 6

    `define BOARD_CK_REF 50000000

    `define BOARD_CK_MUL 4

    `define BOARD_CK_DIV 2

    `define INVRES 1

`endif

`ifdef DIGILENT_SPARTAN3_S200

    `define BOARD_ID 7

    `define BOARD_CK 50000000

`endif

`ifdef ALIEXPRESS_HPC40GBE_K420

    `define BOARD_ID 8

    //`define BOARD_CK 200000000

    `define BOARD_CK_REF 100000000

    `define BOARD_CK_MUL 11

    `define BOARD_CK_DIV 5

    `define XILINX7CLK 1

    `define INVRES 1

`endif

`ifdef QMTECH_ARTIX7_A35

    `define BOARD_ID 9

    `define BOARD_CK_REF 50000000

    `define BOARD_CK_MUL 20

    `define BOARD_CK_DIV 10

    `define XILINX7CLK 1

    `define VIVADO 1

    `define INVRES 1

`endif

`ifndef BOARD_ID

    `define BOARD_ID 0

    `define BOARD_CK 100000000

`endif

`ifdef BOARD_CK_REF

    `define BOARD_CK (`BOARD_CK_REF * `BOARD_CK_MUL / `BOARD_CK_DIV)

`endif

// darkuart baudrate automtically calculated according to board clock:

`ifndef __UARTSPEED__

  `define __UARTSPEED__ 115200

`endif

`define  __BAUD__ ((`BOARD_CK/`__UARTSPEED__))