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`define XULA25

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

//

// Filename:    busmaster.v

//

// Project:     XuLA2 board

//

// Purpose:     This is the highest level, Verilator simulatable, portion of

//              the XuLA2 core.  You should be able to successfully Verilate 

//      this file, and then build a test bench that tests and proves the

//      capability of anything within here.

//

//      In general, this means the file is little more than a wishbone

//      interconnect that connects multiple devices together.  User-JTAG

//      commands come in via i_rx_stb and i_rx_data.  These are converted into

//      wishbone bus interactions, the results of which come back out via

//      o_tx_data and o_tx_stb.

//

//

// Creator:     Dan Gisselquist, Ph.D.

//              Gisselquist Technology, LLC

//

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

//

// Copyright (C) 2015, Gisselquist Technology, LLC

//

// This program is free software (firmware): you can redistribute it and/or

// modify it under the terms of  the GNU General Public License as published

// by the Free Software Foundation, either version 3 of the License, or (at

// your option) any later version.

//

// This program is distributed in the hope that it will be useful, but WITHOUT

// ANY WARRANTY; without even the implied warranty of MERCHANTIBILITY or

// FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License

// for more details.

//

// License:     GPL, v3, as defined and found on www.gnu.org,

//              http://www.gnu.org/licenses/gpl.html

//

//

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

//

//

// Configuration question #1

//

//      What innate capabilities are built into the board?

//

`define INCLUDE_ZIPCPU

// Without the ZipCPU competing for the bus, we don't need to delay it by a

// cycle.

`ifndef INCLUDE_ZIPCPU

`define NO_ZIP_WBU_DELAY

`endif

`ifdef  VERILATOR

`define NO_ZIP_WBU_DELAY

`endif

`define IMPLEMENT_ONCHIP_RAM

`ifndef VERILATOR

`ifndef XULA25

// `define      FANCY_ICAP_ACCESS

`endif

`endif

`define FLASH_ACCESS

`ifdef  XULA25

`define SDCARD_ACCESS

`endif

//

//

// Configuration question #2

//

//      Are any scopes built in to the board?

//

//

// Position #1: The flash scope, or perhaps the wishbone bus/uart/jtag scope

//

// `define      FLASH_SCOPE

`ifndef FLASH_SCOPE

// `define      WBUS_SCOPE // Occupies the FLASH_SCOPE location, so both cannot be active

`endif

//

// Position #2: The ICAP configuration scope, could also be the SDCard scope

// depending on how we configure ourselves here

//

`ifdef  XULA25

`ifdef  FANCY_ICAP_ACCESS

`define CFG_SCOPE // Only defined if we have the access ...

`else

`ifdef  SDCARD_ACCESS

`define SDCARD_SCOPE

`endif

`endif

`endif

//

// Position #3: The SDRAM scope / UART scope (never both)

//

// `define      SDRAM_SCOPE

// `define      UART_SCOPE

//

// Position #4: The Zip CPU scope

//

`ifdef  XULA25

// `define      ZIP_SCOPE

`endif

module  busmaster(i_clk, i_rst,

                i_rx_stb, i_rx_data, o_tx_stb, o_tx_data, i_tx_busy,

                // The SPI Flash lines

                o_sf_cs_n, o_sd_cs_n, o_spi_sck, o_spi_mosi, i_spi_miso,

                // The SDRAM lines

                o_ram_cs_n, o_ram_cke, o_ram_ras_n, o_ram_cas_n,

                        o_ram_we_n, o_ram_bs, o_ram_addr,

                        o_ram_drive_data, i_ram_data, o_ram_data,

                        o_ram_dqm,

                // Generic GPIO

                i_gpio, o_gpio, o_pwm,

                i_rx_uart, o_tx_uart);

        parameter       ZIP_ADDRESS_WIDTH=24, NGPO=15, NGPI=15,

                        ZA=ZIP_ADDRESS_WIDTH;

        input                   i_clk, i_rst;

        // The bus commander, via an external JTAG port

        input                   i_rx_stb;

        input           [7:0]    i_rx_data;

        output  wire            o_tx_stb;

        output  wire    [7:0]    o_tx_data;

        input                   i_tx_busy;

        // SPI flash control

        output  wire            o_sf_cs_n, o_sd_cs_n;

        output  wire            o_spi_sck, o_spi_mosi;

        input                   i_spi_miso;

        // SDRAM control

        output  wire            o_ram_cs_n, o_ram_cke;

        output  wire            o_ram_ras_n, o_ram_cas_n, o_ram_we_n;

        output  wire    [12:0]   o_ram_addr;

        output  wire    [1:0]    o_ram_bs;

        output  wire            o_ram_drive_data;

        input           [15:0]   i_ram_data;

        output  wire    [15:0]   o_ram_data;

        output  wire    [1:0]    o_ram_dqm;

        input   [(NGPI-1):0]     i_gpio;

        output wire [(NGPO-1):0] o_gpio;

        output  wire            o_pwm;

        input                   i_rx_uart;

        output  wire            o_tx_uart;

        //

        //

        // Master wishbone wires

        //

        //

        wire            wb_cyc, wb_stb, wb_we, wb_stall, wb_ack, wb_err;

        wire    [31:0]   wb_data, wb_idata, wb_addr;

        //

        //

        // First BUS master source: The JTAG

        //

        //

        wire    [31:0]   dwb_idata;

        // Wires going to devices

        wire            wbu_cyc, wbu_stb, wbu_we;

        wire    [31:0]   wbu_addr, wbu_data;

        // and then coming from devices

        wire            wbu_ack, wbu_stall, wbu_err;

        wire    [31:0]   wbu_idata;

        // And then headed back home

        wire    w_interrupt;

        // Oh, and the debug control for the ZIP CPU

        wire            wbu_zip_sel, zip_dbg_ack, zip_dbg_stall;

        assign  wbu_zip_sel =((wbu_cyc)&&(wbu_addr[24]));

        wire    [31:0]   zip_dbg_data;

        wire            wbu_dbg;

        wbubus  genbus(i_clk, i_rx_stb, i_rx_data,

                        wbu_cyc, wbu_stb, wbu_we, wbu_addr, wbu_data,

`ifdef  INCLUDE_ZIPCPU

                        ((~wbu_zip_sel)&&(wbu_ack))

                                ||((wbu_zip_sel)&&(zip_dbg_ack)),

                        ((~wbu_zip_sel)&&(wbu_stall))

                                ||((wbu_zip_sel)&&(zip_dbg_stall)),

                                wbu_err, (wbu_zip_sel)?zip_dbg_data:dwb_idata,

`else

                        wbu_ack, wbu_stall,

                                wbu_err, dwb_idata,

`endif

                        w_interrupt,

                        o_tx_stb, o_tx_data, i_tx_busy,

                        wbu_dbg);

        //

        //

        // Second BUS master source: The ZipCPU

        //

        //

        wire            zip_cyc, zip_stb, zip_we, zip_cpu_int;

        wire    [(ZA-1):0]       w_zip_addr;

        wire    [31:0]   zip_addr, zip_data;

        // and then coming from devices

        wire            zip_ack, zip_stall, zip_err;

        wire    dwb_we, dwb_stb, dwb_cyc, dwb_ack, dwb_stall, dwb_err;

        wire    [31:0]   dwb_addr, dwb_odata;

        wire    [8:0]    w_ints_to_zip_cpu;

`ifdef  INCLUDE_ZIPCPU

`ifdef  XULA25

        wire    [31:0]   zip_debug;

        zipsystem #(24'h2000,ZA,9,1,9)

                zippy(i_clk, 1'b0,

                        // Zippys wishbone interface

                        zip_cyc, zip_stb, zip_we, w_zip_addr, zip_data,

                                zip_ack, zip_stall, dwb_idata, zip_err,

                        w_ints_to_zip_cpu, zip_cpu_int,

                        // Debug wishbone interface

                        ((wbu_cyc)&&(wbu_zip_sel)),

                                ((wbu_stb)&&(wbu_zip_sel)),wbu_we, wbu_addr[0],

                                wbu_data,

                                zip_dbg_ack, zip_dbg_stall, zip_dbg_data,

                        zip_debug);

`else

        zipbones #(24'h2000,ZA,8,1)

                zippy(i_clk, 1'b0,

                        // Zippys wishbone interface

                        zip_cyc, zip_stb, zip_we, w_zip_addr, zip_data,

                                zip_ack, zip_stall, dwb_idata, zip_err,

                        w_interrupt, zip_cpu_int,

                        // Debug wishbone interface

                        ((wbu_cyc)&&(wbu_zip_sel)),

                                ((wbu_stb)&&(wbu_zip_sel)),wbu_we, wbu_addr[0],

                                wbu_data,

                                zip_dbg_ack, zip_dbg_stall, zip_dbg_data);

`endif

        generate

        if (ZA < 32)

                assign  zip_addr = { {(32-ZA){1'b0}}, w_zip_addr };

        else

                assign  zip_addr = w_zip_addr;

        endgenerate

        //

        //

        // And an arbiter to decide who gets to access the bus

        //

        //

        /*

        wbarbiter #(32,32) wbu_zip_arbiter(i_clk, i_rst,

                // The UART interface Master

                wbu_addr, wbu_data, wbu_we, (wbu_stb)&&(~wbu_zip_sel),

                        (wbu_cyc)&&(~wbu_zip_sel), wbu_ack, wbu_stall, wbu_err,

                // The ZIP CPU Master

                zip_addr, zip_data, zip_we, zip_stb,

                        zip_cyc, zip_ack, zip_stall, zip_err,

                // Common bus returns

                dwb_addr,dwb_odata,dwb_we,dwb_stb, dwb_cyc, dwb_ack, dwb_stall, dwb_err);

        */

        wbpriarbiter #(32,32) wbu_zip_arbiter(i_clk,

                // The ZIP CPU Master -- gets priority in the arbiter

                zip_cyc, zip_stb, zip_we, zip_addr, zip_data,

                        zip_ack, zip_stall, zip_err,

                // The JTAG interface Master, secondary priority,

                // will suffer a 1clk delay in arbitration

                (wbu_cyc)&&(~wbu_zip_sel), (wbu_stb)&&(~wbu_zip_sel), wbu_we,

                        wbu_addr, wbu_data,

                        wbu_ack, wbu_stall, wbu_err,

                // Common bus returns

                dwb_cyc, dwb_stb, dwb_we, dwb_addr, dwb_odata,

                        dwb_ack, dwb_stall, dwb_err);

        // 

        // 

        // And because the ZIP CPU and the Arbiter create an unacceptable

        // delay, we fail timing.  So we add in a delay cycle ...

        // 

        // 

`ifdef  NO_ZIP_WBU_DELAY

        assign  wb_cyc    = dwb_cyc;

        assign  wb_stb    = dwb_stb;

        assign  wb_we     = dwb_we;

        assign  wb_addr   = dwb_addr;

        assign  wb_data   = dwb_odata;

        assign  dwb_idata = wb_idata;

        assign  dwb_ack   = wb_ack;

        assign  dwb_stall = wb_stall;

        assign  dwb_err   = wb_err;

`else

        busdelay        wbu_zip_delay(i_clk,

                        dwb_cyc, dwb_stb, dwb_we, dwb_addr, dwb_odata,

                                dwb_ack, dwb_stall, dwb_idata, dwb_err,

                        wb_cyc, wb_stb, wb_we, wb_addr, wb_data,

                                wb_ack, wb_stall, wb_idata, wb_err);

`endif

`else // if no ZIP_CPU

        assign  zip_cyc = 1'b0;

        assign  zip_stb = 1'b0;

        assign  zip_we  = 1'b0;

        assign  zip_cpu_int = 1'b0;

        assign  zip_addr = 32'h000;

        assign  zip_data = 32'h000;

        reg     r_zip_dbg_ack;

        initial r_zip_dbg_ack = 1'b0;

        always @(posedge i_clk)

                r_zip_dbg_ack <= ((wbu_cyc)&&(wbu_zip_sel)&(wbu_stb));

        assign  zip_dbg_ack = r_zip_dbg_ack;

        assign  zip_dbg_stall = 1'b0;

        assign  zip_dbg_data = 32'h000;

        assign  dwb_addr = wbu_addr;

        assign  dwb_odata = wbu_data;

        assign  dwb_we = wbu_we;

        assign  dwb_stb = (wbu_stb);

        assign  dwb_cyc = (wbu_cyc);

        assign  wbu_ack = dwb_ack;

        assign  wbu_stall = dwb_stall;

        assign  dwb_idata = wb_idata;

        assign  wbu_err = dwb_err;

`endif

        wire    io_sel, pwm_sel, uart_sel, flash_sel, flctl_sel, scop_sel,

                        cfg_sel, mem_sel, sdram_sel, sdcard_sel,

                        none_sel, many_sel, io_bank;

        wire    io_ack, flash_ack, scop_ack, cfg_ack, mem_ack,

                        sdram_ack, sdcard_ack, uart_ack, pwm_ack;

        wire    io_stall, flash_stall, scop_stall, cfg_stall, mem_stall,

                        sdram_stall, sdcard_stall, uart_stall, pwm_stall;

        wire    [31:0]   io_data, flash_data, scop_data, cfg_data, mem_data,

                        sdram_data, sdcard_data, uart_data, pwm_data;

        reg     [31:0]   bus_err_addr;

        assign  wb_ack = (wb_cyc)&&((io_ack)||(uart_ack)||(pwm_ack)

                                ||(scop_ack)||(cfg_ack)

                                ||(mem_ack)||(flash_ack)||(sdram_ack)

                                ||(sdcard_ack)

                                ||((none_sel)&&(1'b1)));

        assign  wb_stall = ((io_sel)&&(io_stall))

                        ||((uart_sel)&&(uart_stall))

                        ||((pwm_sel)&&(pwm_stall))

                        ||((scop_sel)&&(scop_stall))

                        ||((cfg_sel)&&(cfg_stall))

                        ||((mem_sel)&&(mem_stall))

                        ||((sdram_sel)&&(sdram_stall))

                        ||((sdcard_sel)&&(sdcard_stall))

                        ||((flash_sel||flctl_sel)&&(flash_stall));

                        // (none_sel)&&(1'b0)

        /*

        assign  wb_idata = (io_ack)?io_data

                        : ((scop_ack)?scop_data

                        : ((cfg_ack)?cfg_data

                        : ((mem_ack)?mem_data

                        : ((flash_ack)?flash_data

                        : 32'h00))));

        */

        assign  wb_idata =  (io_ack|scop_ack)?((io_ack )? io_data  : scop_data)

                        : ((uart_ack|pwm_ack)?((uart_ack)?uart_data: pwm_data)

                        : ((cfg_ack) ? cfg_data

                        : ((sdram_ack|sdcard_ack)

                                        ?((sdram_ack)? sdram_data : sdcard_data)

                        : ((mem_ack)?mem_data:flash_data)))); // if (flash_ack)

        assign  wb_err = ((wb_cyc)&&(wb_stb)&&(none_sel || many_sel)) || many_ack;

        // Addresses ...

        //      0000 xxxx       configuration/control registers

        //      001x xxxx       Down-sampler taps       (64 taps, 2 at a time)

        //      1xxx xxxx       Up-sampler taps

        //      1 xxxx xxxx xxxx xxxx xxxx      Up-sampler taps

`ifndef SPEEDY_IO

        wire    pre_io, pre_pwm, pre_uart, pre_flctl, pre_scop;

        assign  io_bank  = (wb_cyc)&&(wb_addr[31:5] == 27'h8);

        assign  pre_io   = (~pre_flctl)&&(~pre_pwm)&&(~pre_uart)&&(~pre_scop);

        assign  io_sel   = (io_bank)&&(pre_io);

        assign  pre_pwm  = (wb_addr[4: 1]== 4'h4);

        assign  pwm_sel  = (io_bank)&&(pre_pwm);

        assign  pre_uart = (wb_addr[4: 1]== 4'h5)||(wb_addr[4:0]==5'h7);

        assign  uart_sel = (io_bank)&&(pre_uart);

        assign  pre_flctl= (wb_addr[4: 2]== 3'h3);

        assign  flctl_sel= (io_bank)&&(pre_flctl);

        assign  pre_scop = (wb_addr[4: 3]== 2'h3);

        assign  scop_sel = (io_bank)&&(pre_scop);

        assign  cfg_sel  =((wb_cyc)&&(wb_addr[31: 6]== 26'h05));

        // zip_sel is not on the bus at this point

        assign  mem_sel  =((wb_cyc)&&(wb_addr[31:13]== 19'h01));

        assign  flash_sel=((wb_cyc)&&(wb_addr[31:18]== 14'h01));

`ifdef  SDCARD_ACCESS

        assign  sdcard_sel=((wb_cyc)&&(wb_addr[31:2]== 30'h48));

`else

        assign  sdcard_sel=1'b0;

`endif

        assign  sdram_sel=((wb_cyc)&&(wb_addr[31:23]== 9'h01));

`else

        // While the following would make the bus infinitely easier to decode,

        // it would also scramble where everything on the bus is located at,

        // while also making it difficult to access these values via offsets

        // of a register.  Further, while simpler, everything would alias all

        // over the place as well--that is, devices would show up at multiple

        // locations on the bus.  It's all a tradeoff.

        assign  iovec = { wb_addr[23],wb_addr[18],wb_addr[15:13] }

        assign  sdram_sel =((wb_cyc)&&(io_vec[4]));

        assign  flash_sel =((wb_cyc)&&(io_vec[4:3]==2'b01));

        assign  mem_sel   =((wb_cyc)&&(io_vec[4:0]==5'h07));

        assign  cfg_sel   =((wb_cyc)&&(io_vec[4:0]==5'h06));

`ifdef  SDCARD_ACCESS

        assign  sdcard_sel=((wb_cyc)&&(io_vec[4:0]==5'h05));

`else

        assign  sdcard_sel=1'b0;

`endif

        assign  scop_sel  =((wb_cyc)&&(io_vec[4:0]==5'h04));

        assign  rtc_sel   =((wb_cyc)&&(io_vec[4:0]==5'h03));

        assign  rtc_sel   =((wb_cyc)&&(io_vec[4:0]==5'h03));

        assign  puf_sel   =((wb_cyc)&&(io_vec[4:0]==5'h02));

        assign  io_sel    =((wb_cyc)&&(io_vec[4:0]==5'h01));

        assign  wb_err    =((wb_cyc)&&(io_vec[4:0]==5'h00));

        assign  flctl_sel = (puf_sel)&&(wb_addr[3]);

        assign  pwm_sel   = (puf_sel)&&(wb_addr[3:2]==2'b00);

        // Note that in the following definition, the UART is given four words

        // despite the fact that it can probably only use 3.

        assign  uart_sel  = (puf_sel)&&(wb_addr[3:2]==2'b01);

`endif

        assign  none_sel =((wb_cyc)&&(wb_stb)&&(~

                        (io_sel

                        ||uart_sel

                        ||pwm_sel

                        ||flctl_sel

                        ||scop_sel

                        ||cfg_sel

                        ||mem_sel

                        ||sdram_sel

                        ||sdcard_sel

                        ||flash_sel)));

        assign  many_sel =((wb_cyc)&&(wb_stb)&&(

                         {3'h0, io_sel}

                        +{3'h0, uart_sel}

                        +{3'h0, pwm_sel}

                        +{3'h0, flctl_sel}

                        +{3'h0, scop_sel}

                        +{3'h0, cfg_sel}

                        +{3'h0, mem_sel}

                        +{3'h0, sdram_sel}

                        +{3'h0, sdcard_sel}

                        +{3'h0, flash_sel} > 1));

        wire    many_ack;

        assign  many_ack =((wb_cyc)&&(

                         {3'h0, io_ack}

                        +{3'h0, uart_ack}

                        +{3'h0, pwm_ack}

                        // FLCTL acks through the flash, so one less check here

                        +{3'h0, scop_ack}

                        +{3'h0, cfg_ack}

                        +{3'h0, mem_ack}

                        +{3'h0, sdram_ack}

                        +{3'h0, sdcard_ack}

                        +{3'h0, flash_ack} > 1));

        always @(posedge i_clk)

                if (wb_err)

                        bus_err_addr <= wb_addr;

        wire            flash_interrupt, sdcard_interrupt, scop_interrupt,

                        uart_rx_int, uart_tx_int, pwm_int;

        wire    [(NGPO-1):0]     w_gpio;

        // The I/O processor, herein called an ioslave

        ioslave #(NGPO, NGPI) runio(i_clk,

                        wb_cyc, (io_sel)&&(wb_stb), wb_we, wb_addr[4:0],

                                wb_data, io_ack, io_stall, io_data,

                        i_gpio, w_gpio,

                        bus_err_addr,

                        {

                        sdcard_interrupt,

                        uart_tx_int, uart_rx_int, pwm_int, scop_interrupt,

                                flash_interrupt,

`ifdef  XULA25

                                zip_cpu_int

`else

                                1'b0

`endif

                                },

                        w_ints_to_zip_cpu,

                        w_interrupt);

                // 8684

                // 1'bx, 4'h0, scop_sel, scop_ack, ~scop_stall, 

                //      wb_err, ~vga_interrupt, 2'b00, flash_interrupt

        //

        //

        //      UART device

        //

        wire    [31:0]   uart_debug;

        uartdev serialport(i_clk, i_rx_uart, o_tx_uart,

                        wb_cyc, (wb_stb)&&(uart_sel), wb_we,

                                        { ~wb_addr[2], wb_addr[0]}, wb_data,

                        uart_ack, uart_stall, uart_data,

                        uart_rx_int, uart_tx_int,

                        uart_debug);

        //

        //      PWM (audio) device

        //

        // The audio rate is given by the number of clock ticks between

        // samples.  If we are running at 80 MHz, then divide that by the

        // sample rate to get the first parameter for the PWM device.  The

        // second parameter is zero or one, indicating whether or not the

        // audio rate can be adjusted (1), or whether it is fixed within the

        // build (0).

`ifdef  XULA25

`define FMHACK

`ifdef  FMHACK

        wbfmtxhack      #(16'd1813)     // 44.1 kHz, user adjustable

`else

        wbpwmaudio      #(16'd1813,1)   // 44.1 kHz, user adjustable

`endif

`else

        wbpwmaudio      #(16'h270f,0,16) //  8   kHz, fixed audio rate

`endif

                pwmdev(i_clk,

                        wb_cyc, (wb_stb)&&(pwm_sel), wb_we, wb_addr[0],

                        wb_data, pwm_ack, pwm_stall, pwm_data, o_pwm, pwm_int);

`ifdef  FMHACK

        assign  o_gpio = {(NGPO){o_pwm}};

`else

        assign  o_gpio = w_gpio;

`endif

        //

        //      FLASH MEMORY CONFIGURATION ACCESS

        //

        wire    flash_cs_n, flash_sck, flash_mosi;

        wire    spi_user, sdcard_grant, flash_grant;

`ifdef  FLASH_ACCESS

        wbspiflash      flashmem(i_clk,

                wb_cyc,(wb_stb&&flash_sel),(wb_stb)&&(flctl_sel),wb_we,

                        wb_addr[17:0], wb_data,

                flash_ack, flash_stall, flash_data,

                flash_sck, flash_cs_n, o_sf_cs_n, flash_mosi, i_spi_miso,

                flash_interrupt, flash_grant);

`else

        reg     r_flash_ack;

        initial r_flash_ack = 1'b0;

        always @(posedge i_clk)

                r_flash_ack <= (wb_cyc)&&(wb_stb)&&((flash_sel)||(flctl_sel));

        assign  flash_ack = r_flash_ack;

        assign  flash_stall = 1'b0;

        assign  flash_data = 32'h0000;

        assign  flash_interrupt = 1'b0;

        assign  flash_cs_n = 1'b1;

        assign  flash_sck  = 1'b1;

        assign  flash_mosi = 1'b1;

`endif

        //

        //      SDCARD ACCESS

        //

        wire    sdcard_cs_n, sdcard_sck, sdcard_mosi;

        wire    [31:0]   sdspi_scope;

`ifdef  SDCARD_ACCESS

        sdspi   sdcard_controller(i_clk,

                // Wishbone interface

                wb_cyc, (wb_stb)&&(sdcard_sel), wb_we, wb_addr[1:0], wb_data,

                //      return

                        sdcard_ack, sdcard_stall, sdcard_data,

                // SPI interface

                sdcard_cs_n, sdcard_sck, sdcard_mosi, i_spi_miso,

                sdcard_interrupt, sdcard_grant, sdspi_scope);

`else

        reg     r_sdcard_ack;

        initial r_sdcard_ack = 1'b0;

        always @(posedge i_clk)

                r_sdcard_ack <= (wb_cyc)&&(wb_stb)&&(sdcard_sel);

        assign  sdcard_stall = 1'b0;

        assign  sdcard_ack = r_sdcard_ack;

        assign  sdcard_data = 32'h0000;

        assign  sdcard_interrupt= 1'b0;

`endif  // SDCARD_ACCESS

`ifdef  FLASH_ACCESS

`ifdef  SDCARD_ACCESS

        spiarbiter      spichk(i_clk,

                // Channel zero

                flash_cs_n, flash_sck, flash_mosi,

                // Channel one

                sdcard_cs_n, sdcard_sck, sdcard_mosi,

                o_sf_cs_n, o_sd_cs_n, o_spi_sck, o_spi_mosi,

                spi_user);

        assign  sdcard_grant =  spi_user;

        assign  flash_grant  = ~spi_user;

`else

        // Flash access, but no SD card access