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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,
		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;
	memdev	#(.LGMEMSZ(LGMEMSZ))
		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;

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