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// Filename: busmaster.v
// Project: CMod S6 System on a Chip, ZipCPU demonstration project
// Purpose: This is the highest level, simulatable, file in the S6SoC
// project--of that portion of the project that includes the
// ZipCPU. This portion therefore contains references to all of the
// masters (ZipCPU) and slaves (flash, block RAM, I/O, Scope) on the
// wishbone bus, and connects them all together. Hence, this contains
// the wishbone interconnect logic as well.
// Creator: Dan Gisselquist, Ph.D.
// Gisselquist Technology, LLC
// Copyright (C) 2015-2017, 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.
// You should have received a copy of the GNU General Public License along
// with this program. (It's in the $(ROOT)/doc directory, run make with no
// target there if the PDF file isn't present.) If not, see
// <> for a copy.
// License: GPL, v3, as defined and found on,
`include "builddate.v"
`define DBG_SCOPE // About 204 LUTs, at 2^6 addresses
`define HAS_RXUART
`define LOWLOGIC_FLASH // Saves about 154 LUTs
`define USE_LITE_UART // Saves about 55 LUTs
module busmaster(i_clk, i_rst,
i_uart, o_uart_rts_n, o_uart, i_uart_cts_n,
// The SPI Flash lines
o_qspi_cs_n, o_qspi_sck, o_qspi_dat, i_qspi_dat, o_qspi_mod,
// The board I/O
i_btn, o_led, o_pwm, o_pwm_aux,
// Keypad connections
i_kp_row, o_kp_col,
// GPIO lines
i_gpio, o_gpio);
parameter BUS_ADDRESS_WIDTH=23,
UART_SETUP = 31'd25;
BAW=BUS_ADDRESS_WIDTH; // 24bits->2,258,23b->2181
// 2^14 bytes requires a LGMEMSZ of 14, and 12 address bits ranging from
// 0 to 11. As with many other devices, the wb_cyc line is more for
// form than anything else--it is ignored by the memory itself.
localparam LGMEMSZ=14; // Takes 8 BLKRAM16 elements for LGMEMSZ=14
// As with the memory size, the flash size is also measured in log_2 of
// the number of bytes.
localparam LGFLASHSZ = 24;
input i_clk, i_rst;
// UART parameters
input i_uart, i_uart_cts_n;
output wire o_uart, o_uart_rts_n;
// SPI flash control
output wire o_qspi_cs_n;
output wire [1:0] o_qspi_sck;
output wire o_qspi_sck;
output wire [3:0] o_qspi_dat;
input [3:0] i_qspi_dat;
output wire [1:0] o_qspi_mod;
// Board I/O
input [1:0] i_btn;
output wire [3:0] o_led;
output wire o_pwm;
output wire [1:0] o_pwm_aux;
// Keypad
input [3:0] i_kp_row;
output wire [3:0] o_kp_col;
// GPIO liines
input [15:0] i_gpio;
output wire [15:0] o_gpio;
// Master wishbone wires
wire wb_cyc, wb_stb, wb_we, wb_stall, wb_ack, wb_err;
wire [31:0] wb_data, wb_idata;
wire [3:0] wb_sel;
wire [(BAW-1):0] wb_addr;
// Wires going to devices
// And then headed back home
wire w_interrupt;
// Oh, and the debug control for the ZIP CPU
wire zip_dbg_ack, zip_dbg_stall;
wire [31:0] zip_dbg_data;
// The BUS master (source): The ZipCPU
wire zip_cyc, zip_stb, zip_we, zip_cpu_int;
wire [(ZA-1):0] w_zip_addr;
wire [(BAW-1):0] zip_addr;
wire [31:0] zip_data, zip_scope_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 [(BAW-1):0] dwb_addr;
wire [31:0] dwb_odata;
wire cpu_reset, watchdog_int;
reg btn_reset, x_button, r_button;
initial btn_reset = 1'b0;
initial x_button = 1'b0;
initial r_button = 1'b0;
always @(posedge i_clk)
x_button <= i_btn[1];
r_button <= x_button;
btn_reset <= ((r_button)&&(zip_cpu_int))||(watchdog_int);
assign cpu_reset = btn_reset;
assign cpu_reset = (watchdog_int);
swic(i_clk, cpu_reset, // 1'b0,
// Zippys wishbone interface
wb_cyc, wb_stb, wb_we, w_zip_addr, wb_data, wb_sel,
wb_ack, wb_stall, wb_idata, wb_err,
w_interrupt, zip_cpu_int,
// Debug wishbone interface -- not really used
1'b0, 1'b0,1'b0, 1'b0, 32'h00,
zip_dbg_ack, zip_dbg_stall, zip_dbg_data,
if (ZA < BAW)
assign wb_addr = { {(BAW-ZA){1'b0}}, w_zip_addr };
assign wb_addr = w_zip_addr;
// Signals to build/detect bus errors
wire none_sel, many_sel;
wire io_sel, flash_sel, flctl_sel, scop_sel, mem_sel;
wire flash_ack, scop_ack, cfg_ack, mem_ack, many_ack;
wire io_stall, flash_stall, scop_stall, cfg_stall, mem_stall;
reg io_ack;
wire [31:0] flash_data, scop_data, cfg_data, mem_data, pwm_data,
spio_data, gpio_data, uart_data;
reg [31:0] io_data;
reg [(BAW-1):0] bus_err_addr;
// wb_ack
// The returning wishbone ack is equal to the OR of every component that
// might possibly produce an acknowledgement, gated by the CYC line. To
// add new components, OR their acknowledgements in here.
// Note the reference to none_sel. If nothing is selected, the result
// is an error. Here, we do nothing more than insure that the erroneous
// request produces an ACK ... if it was ever made, rather than stalling
// the bus.
assign wb_ack = (wb_cyc)&&((io_ack)||(scop_ack)
// wb_stall
// The returning wishbone stall line really depends upon what device
// is requested. Thus, if a particular device is selected, we return
// the stall line for that device.
// To add a new device, simply and that devices select and stall lines
// together, and OR the result with the massive OR logic below.
assign wb_stall = ((io_sel)&&(io_stall))
// (none_sel)&&(1'b0)
// wb_idata
// This is the data returned on the bus. Here, we select between a
// series of bus sources to select what data to return. The basic
// logic is simply this: the data we return is the data for which the
// ACK line is high.
// The last item on the list is chosen by default if no other ACK's are
// true. Although we might choose to return zeros in that case, by
// returning something we can skimp a touch on the logic.
// To add another device, add another ack check, and another closing
// parenthesis.
assign wb_idata = (io_ack|scop_ack)?((io_ack )? io_data : scop_data)
: ((mem_ack)?(mem_data)
: flash_data);
// wb_err
// This is the bus error signal. It should never be true, but practice
// teaches us otherwise. Here, we allow for three basic errors:
// 1. STB is true, but no devices are selected
// This is the null pointer reference bug. If you try to access
// something on the bus, at an address with no mapping, the bus
// should produce an error--such as if you try to access something
// at zero.
// 2. STB is true, and more than one device is selected
// (This can be turned off, if you design this file well. For
// this line to be true means you have a design flaw.)
// 3. If more than one ACK is every true at any given time.
// This is a bug of bus usage, combined with a subtle flaw in the
// WB pipeline definition. You can issue bus requests, one per
// clock, and if you cross device boundaries with your requests,
// you may have things come back out of order (not detected here)
// or colliding on return (detected here). The solution to this
// problem is to make certain that any burst request does not cross
// device boundaries. This is a requirement of whoever (or
// whatever) drives the bus.
assign wb_err = ((wb_stb)&&(none_sel || many_sel)) || many_ack;
// Addresses ...
// dev_sel
// The device select lines
// The skipaddr bitfield below is our cheaters way of handling
// device selection. We grab particular wires from the bus to do
// this, and ignore all others. While this may lead to some
// surprising results for the CPU when it tries to access an
// inappropriate address, it also minimizes our logic while also
// placing every address at the right address. The only problem is
// ... devices will also be at some unexpected addresses, but ... this
// is still within our spec.
wire [3:0] skipaddr;
assign skipaddr = {
wb_addr[(LGFLASHSZ-2)], // Flash
wb_addr[(LGMEMSZ-2)], // RAM
wb_addr[ 9], // SCOPE
wb_addr[ 8] }; // I/O
// This might not be the most efficient way in hardware, but it will
// work for our purposes here. There are two phantom bits for each
// of these ... bits that tell the CPU which byte within the word, and
// another phantom bit because we allocated a minimum of two words to
// every device.
wire idle_n;
assign idle_n = wb_stb;
assign idle_n = 1'b1;
// `define ZERO_ON_IDLE
assign idle_n = (wb_cyc)&&(wb_stb);
assign idle_n = 1'b1;
assign io_sel =((idle_n)&&(skipaddr[3:0]==4'h1));
assign scop_sel =((idle_n)&&(skipaddr[3:1]==3'h1)); // = 4'h2
assign flctl_sel= 1'b0; // ((wb_cyc)&&(skipaddr[3:0]==4'h3));
assign mem_sel =((idle_n)&&(skipaddr[3:2]==2'h1));
assign flash_sel=((idle_n)&&(skipaddr[3]));
// none_sel
// This wire is true if wb_stb is true and no device is selected. This
// is an error condition, but here we present the logic to test for it.
// If you add another device, add another OR into the select lines
// associated with this term.
assign none_sel =((wb_stb)&&(skipaddr==4'h0));
// many_sel
// This should *never* be true .... unless you mess up your address
// decoding logic. Since I've done that before, I test/check for it
// here.
// To add a new device here, simply add it to the list. Make certain
// that the width of the add, however, is greater than the number
// of devices below. Hence, for 3 devices, you will need an add
// at least 3 bits in width, for 7 devices you will need at least 4
// bits, etc.
// Because this add uses the {} operator, the individual components to
// it are by default unsigned ... just as we would like.
// There's probably another easier/better/faster/cheaper way to do this,
// but I haven't found any such that are also easier to adjust with
// new devices. I'm open to options.
assign many_sel = 1'b0;
// many_ack
// Normally this would capture the error when multiple things creates acks
// at the same time. The S6 is small, though, and doesn't have the logic
// we need to do this right. Hence we just declare (and hope) that this
// will never be true and work with that.
assign many_ack = 1'b0;
wire flash_interrupt, scop_interrupt, timer_int,
gpio_int, pwm_int, keypad_int,button_int;
// bus_err_addr
// We'd like to know, after the fact, what (if any) address caused a
// bus error. So ... if we get a bus error, let's record the address
// on the bus for later analysis.
initial bus_err_addr = 0;
always @(posedge i_clk)
if (wb_err)
bus_err_addr <= wb_addr;
// Interrupt processing
// The interrupt controller will be used to tell us if any interrupts
// take place.
// To add more interrupts, you can just add more wires to this
// int_vector.
reg rx_rdy;
wire [10:0] int_vector;
assign int_vector = {
gpio_int, pwm_int, keypad_int,
(!tx_stb), rx_rdy,
1'b0, timer_int,
1'b0, scop_interrupt,
wb_err, button_int };
wire [31:0] pic_data;
icontrol #(11) pic(i_clk, 1'b0, (wb_stb)&&(io_sel)
wb_data, pic_data, int_vector, w_interrupt);
wire [31:0] timer_data, watchdog_data;
wire zta_ack, zta_stall, ztb_ack, ztb_stall;
ziptimer #(32,31,1)
thetimer(i_clk, 1'b0, 1'b1, wb_cyc,
wb_we, wb_data, zta_ack, zta_stall, timer_data,
ziptimer #(32,31,0)
watchdog(i_clk, cpu_reset, 1'b1, wb_cyc,
wb_we, wb_data, ztb_ack, ztb_stall, watchdog_data,
always @(posedge i_clk)
4'h0: io_data <= pic_data;
4'h1: io_data <= { {(30-BAW){1'b0}}, bus_err_addr, 2'b00 };
4'h2: io_data <= timer_data;
4'h3: io_data <= watchdog_data;
4'h4: io_data <= pwm_data;
4'h5: io_data <= spio_data;
4'h6: io_data <= gpio_data;
4'h7: io_data <= uart_data;
default: io_data <= `DATESTAMP;
// 4'h8: io_data <= `DATESTAMP;
always @(posedge i_clk)
io_ack <= (wb_stb)&&(io_sel);
assign io_stall = 1'b0;
wire pwm_ack, pwm_stall;
wbpwmaudio #(14'd10000,2,0,14)
theaudio(i_clk, wb_cyc,
wb_we, 1'b0, wb_data,
pwm_ack, pwm_stall, pwm_data, o_pwm,
o_pwm_aux, //={pwm_shutdown_n,pwm_gain}
// Special Purpose I/O: Keypad, button, LED status and control
wire [3:0] w_led;
spio thespio(i_clk, wb_cyc,(wb_stb)&&(io_sel)&&(wb_addr[3:0]==4'h5),
wb_we, wb_data, spio_data,
o_kp_col, i_kp_row, i_btn, w_led,
keypad_int, button_int);
assign o_led = { w_led[3]|w_interrupt,w_led[2]|zip_cpu_int,
w_led[1], w_led[0] };
// General purpose (sort of) I/O: (Bottom two bits robbed in each
// direction for an I2C link at the toplevel.v design)
wbgpio #(16,16,16'hffff) thegpio(i_clk, wb_cyc,
(wb_stb)&&(io_sel)&&(wb_addr[3:0]==4'h6), wb_we,
wb_data, gpio_data, i_gpio, o_gpio, gpio_int);
// UART device: our console
wire [30:0] uart_setup;
wire rx_break, rx_parity_err, rx_frame_err, rx_ck_uart, rx_stb;
wire [7:0] rx_data;
assign uart_setup = UART_SETUP;
rxuartlite #(UART_SETUP[23:0])
rcvuart(i_clk, i_uart, rx_stb, rx_data);
assign rx_break = 1'b0;
assign rx_parity_err = 1'b0;
assign rx_frame_err = 1'b0;
assign rx_ck_uart = 1'b0;
rxuart #(UART_SETUP)
rcvuart(i_clk, 1'b0, uart_setup, i_uart, rx_stb, rx_data,
rx_break, rx_parity_err, rx_frame_err, rx_ck_uart);
assign rx_break = 1'b0;
assign rx_parity_err = 1'b0;
assign rx_frame_err = 1'b0;
assign rx_ck_uart = 1'b0;
assign rx_stb = 1'b0;
assign rx_data = 8'h0;
wire tx_break, tx_busy;
reg tx_stb;
reg [7:0] tx_data;
assign tx_break = 1'b0;
txuartlite #(UART_SETUP[23:0])
tcvuart(i_clk, tx_stb, tx_data, o_uart, tx_busy);
txuart #(UART_SETUP)
tcvuart(i_clk, 1'b0, uart_setup, tx_break, tx_stb, tx_data,
i_uart_cts_n, o_uart, tx_busy);
// Rudimentary serial port control
reg [7:0] r_rx_data;
// Baud rate is set by clock rate / baud rate.
initial tx_stb = 1'b0;
initial tx_data = 8'h00;
always @(posedge i_clk)
if ((wb_stb)&&(io_sel)&&(wb_addr[3:0]==4'h7)&&(wb_we))
tx_data <= wb_data[7:0];
tx_stb <= 1'b1;
else if ((tx_stb)&&(!tx_busy))
tx_stb <= 1'b0;
initial rx_rdy = 1'b0;
always @(posedge i_clk)
if (rx_stb)
r_rx_data <= rx_data;
always @(posedge i_clk)
rx_rdy <= rx_stb;
rx_rdy <= (rx_rdy | rx_stb);
assign o_uart_rts_n = (rx_rdy);
assign uart_data = { 23'h0, !rx_rdy, r_rx_data };
assign o_uart_rts_n = 1'b1;
assign uart_data = 32'h00;
// uart_ack gets returned as part of io_ack, since that happens when
// io_sel and wb_stb are defined
// always @(posedge i_clk)
// uart_ack<= ((wb_stb)&&(io_sel)&&(wb_addr[3:0]==4'h7));
qflashxpress flashmem(i_clk, 1'b0,
flash_ack, flash_stall, flash_data,
o_qspi_sck, o_qspi_cs_n, o_qspi_mod, o_qspi_dat, i_qspi_dat);
assign flash_interrupt = 1'b0;
wbqspiflash #(LGFLASHSZ) flashmem(i_clk,
wb_addr[(LGFLASHSZ-3):0], wb_data,
flash_ack, flash_stall, flash_data,
o_qspi_sck, o_qspi_cs_n, o_qspi_mod, o_qspi_dat, i_qspi_dat,
reg r_flash_ack;
initial r_flash_ack = 1'b0;
always @(posedge i_clk)
r_flash_ack <= (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 o_qspi_sck = 1'b1;
assign o_qspi_cs_n = 1'b1;
assign o_qspi_mod = 2'b01;
assign o_qspi_dat = 4'b1111;
ram(i_clk, wb_cyc, (wb_stb)&&(mem_sel), wb_we,
wb_addr[(LGMEMSZ-3):0], wb_data, wb_sel,
mem_ack, mem_stall, mem_data);
assign mem_data = 32'h00;
assign mem_stall = 1'b0;
reg r_mem_ack;
always @(posedge i_clk)
r_mem_ack <= (wb_stb)&&(mem_sel);
assign mem_ack = r_mem_ack;
wire [31:0] scop_cpu_data;
wire scop_cpu_ack, scop_cpu_stall, scop_cpu_interrupt;
`ifdef DBG_SCOPE
wire scop_trigger = (zip_cpu_int) || (cpu_reset);
wbscopc #(5'ha)
wbscope #(.LGMEM(5'h6), .HOLDOFFBITS(9))
cpuscope(i_clk, 1'b1, scop_trigger,
// cfg_scope[30:0],
// cfg_scope[31:0],
// Wishbone interface
i_clk, wb_cyc, (wb_stb)&&(scop_sel),
wb_we, wb_addr[0], wb_data,
scop_cpu_ack, scop_cpu_stall, scop_cpu_data,
reg r_scop_cpu_ack;
always @(posedge i_clk)
r_scop_cpu_ack <= (wb_stb)&&(scop_sel);
assign scop_cpu_ack = r_scop_cpu_ack;
assign scop_cpu_data = 32'h000;
assign scop_cpu_stall= 1'b0;
assign scop_interrupt = scop_cpu_interrupt;
assign scop_ack = scop_cpu_ack;
assign scop_stall = scop_cpu_stall;
assign scop_data = scop_cpu_data;