working serial port for console and ppp (#6)

MacPlus.qsf

@@ -13,7 +13,7 @@ set_global_assignment -name PARTITION_NETLIST_TYPE SOURCE -section_id Top
 set_global_assignment -name PARTITION_FITTER_PRESERVATION_LEVEL PLACEMENT_AND_ROUTING -section_id Top
 set_global_assignment -name PARTITION_COLOR 16764057 -section_id Top
 
-set_global_assignment -name LAST_QUARTUS_VERSION "17.0.2 Standard Edition"
+set_global_assignment -name LAST_QUARTUS_VERSION "17.0.2 Lite Edition"
 
 set_global_assignment -name GENERATE_RBF_FILE ON
 set_global_assignment -name PROJECT_OUTPUT_DIRECTORY output_files

MacPlus.sv

@@ -175,7 +175,7 @@ module emu
 
 assign ADC_BUS  = 'Z;
 assign USER_OUT = '1;
-assign {UART_RTS, UART_TXD, UART_DTR} = 0;
+
 assign {DDRAM_CLK, DDRAM_BURSTCNT, DDRAM_ADDR, DDRAM_DIN, DDRAM_BE, DDRAM_RD, DDRAM_WE} = 0; 
 assign {SD_SCK, SD_MOSI, SD_CS} = 'Z;
 
@@ -201,7 +201,7 @@ video_freak video_freak
 
 `include "build_id.v" 
 localparam CONF_STR = {
-	"MACPLUS;;",
+	"MACPLUS;UART115200;",
 	"-;",
 	"F1,DSK,Mount Pri Floppy;",
 	"F2,DSK,Mount Sec Floppy;",
@@ -216,6 +216,8 @@ localparam CONF_STR = {
 	"ODE,CPU,68000,68010,68020;",
 	"O4,Memory,1MB,4MB;",
 	"-;",
+	//"OA,Serial,Off,On;",
+	//"-;",
 	"R0,Reset & Apply CPU+Memory;",
 	"V,v",`BUILD_DATE
 };
@@ -358,11 +360,44 @@ assign AUDIO_MIX = 0;
 
 
 // set the real-world inputs to sane defaults
-localparam serialIn = 1'b0,
+localparam 	  configROMSize = 1'b1;  // 128K ROM
-			  configROMSize = 1'b1;  // 128K ROM
 
 wire [1:0] configRAMSize = status_mem?2'b11:2'b10; // 1MB/4MB
 			  
+//
+// Serial Ports
+//
+wire serialOut;
+wire serialIn;
+wire serialCTS;
+wire serialRTS;
+
+/*
+assign serialIn = ~status[10] ? 0 : UART_RXD;
+assign UART_TXD = serialOut;
+assign serialCTS = UART_CTS;
+assign UART_RTS = serialRTS;
+assign UART_DTR = UART_DSR;
+*/
+
+//assign serialIn = ~status[10] ? 0 : UART_RXD;
+assign serialIn =  UART_RXD;
+assign UART_TXD = serialOut;
+//assign UART_RTS = UART_CTS;
+assign UART_RTS = serialRTS ;
+assign UART_DTR = UART_DSR;
+
+//assign {UART_RTS, UART_TXD, UART_DTR} = 0;
+/*
+	input         UART_CTS,
+	output        UART_RTS,
+	input         UART_RXD,
+	output        UART_TXD,
+	output        UART_DTR,
+	input         UART_DSR,
+*/
+
+
 // interconnects
 // CPU
 wire clk8, _cpuReset, _cpuReset_o, _cpuUDS, _cpuLDS, _cpuRW, _cpuAS;
@@ -618,7 +653,13 @@ dataController_top dc0
 	.ps2_key(ps2_key), 
 	.capslock(capslock),
 	.ps2_mouse(ps2_mouse),
+	// serial uart
 	.serialIn(serialIn),
+	.serialOut(serialOut),
+	.serialCTS(serialCTS),
+	.serialRTS(serialRTS),
+
+	// rtc unix ticks
 	.timestamp(TIMESTAMP),
 
 	// video

files.qip

@@ -8,6 +8,8 @@ set_global_assignment -name VERILOG_FILE rtl/floppy.v
 set_global_assignment -name SYSTEMVERILOG_FILE rtl/ps2_kbd.sv
 set_global_assignment -name VERILOG_FILE rtl/ps2_mouse.v
 set_global_assignment -name VERILOG_FILE rtl/scc.v
+set_global_assignment -name VERILOG_FILE rtl/uart/txuart.v
+set_global_assignment -name VERILOG_FILE rtl/uart/rxuart.v
 set_global_assignment -name VERILOG_FILE rtl/iwm.v
 set_global_assignment -name VHDL_FILE rtl/via6522.vhd
 set_global_assignment -name VERILOG_FILE rtl/addrDecoder.v

rtl/dataController_top.v

@@ -47,6 +47,8 @@ module dataController_top(
 	// serial:
 	input serialIn, 
 	output serialOut,	
+	input serialCTS,
+	output serialRTS,
 
 	// RTC
 	input [32:0] timestamp,
@@ -148,8 +150,6 @@ module dataController_top(
 		!_sccIrq?3'b101:
 		3'b111;
 		
-	// Serial port
-	assign serialOut = 0;
 
 	reg [15:0] cpu_data;
 	always @(posedge clk32) if (cpuBusControl && memoryLatch) cpu_data <= memoryDataIn;
@@ -409,8 +409,13 @@ module dataController_top(
 		._irq(_sccIrq),
 		.dcd_a(mouseX1),
 		.dcd_b(mouseY1),
-		.wreq(sccWReq));
+		.wreq(sccWReq),
-		
+		.txd(serialOut),
+		.rxd(serialIn),
+		.cts(serialCTS),
+		.rts(serialRTS)
+		);
+				
 	// Video
 	videoShifter vs(
 		.clk32(clk32), 

rtl/ps2_kbd.sv

@@ -22,7 +22,7 @@ module ps2_kbd
 
 reg   [8:0] keymac;
 reg			key_pending;
-reg  [21:0] pacetimer;
+reg  [19:0] pacetimer;
 reg			inquiry_active;
 reg 			cmd_inquiry;
 reg 			cmd_instant;
@@ -68,8 +68,8 @@ always@(posedge clk or posedge reset) begin
 	end
 end
 
-wire tick_long  = pacetimer == 22'h3fffff;
+wire tick_long  = pacetimer == 20'hfffff;
-wire tick_short = pacetimer == 22'h000fff;
+wire tick_short = pacetimer == 20'h00fff;
 
 /* Delay inquiry responses to after tick_short */
 always@(posedge clk or posedge reset) begin

rtl/scc.v

@@ -62,7 +62,8 @@ module scc
 	wire		reset;
 
 	/* Data registers */
-	reg [7:0] 	data_a = 0;
+//	reg [7:0] 	data_a = 0;
+	wire[7:0] 	data_a ;
 	reg [7:0] 	data_b = 0;
 
 	/* Read registers */
@@ -84,6 +85,10 @@ module scc
 	reg [7:0] 	wr1_a;
 	reg [7:0] 	wr1_b;
 	reg [7:0] 	wr2;
+	reg [7:0] 	wr3_a;   /* synthesis keep */
+	reg [7:0] 	wr3_b;
+	reg [7:0] 	wr4_a;
+	reg [7:0] 	wr4_b;
 	reg [7:0] 	wr5_a;
 	reg [7:0] 	wr5_b;
 	reg [7:0] 	wr6_a;
@@ -105,8 +110,10 @@ module scc
 	/* Status latches */
 	reg		latch_open_a;
 	reg		latch_open_b;
+	reg		cts_latch_a;
 	reg		dcd_latch_a;
 	reg		dcd_latch_b;
+	wire		cts_ip_a;
 	wire		dcd_ip_a;
 	wire		dcd_ip_b;
 	wire		do_latch_a;
@@ -125,6 +132,10 @@ module scc
 	reg		ex_irq_ip_b;
 	wire [2:0] 	rr2_vec_stat;	
 
+	reg [7:0] tx_data_a;
+	reg wr8_wr_a;
+	reg wr8_wr_b;
+		
 	/* Register/Data access helpers */
 	assign wreg_a  = cs & we & (~rs[1]) &  rs[0];
 	assign wreg_b  = cs & we & (~rs[1]) & ~rs[0];
@@ -136,11 +147,28 @@ module scc
 	/* Register index is set by a write to WR0 and reset
 	 * after any subsequent write. We ignore the side
 	 */
-	always@(posedge clk or posedge reset) begin
+	reg wr_data_a;
+	reg wr_data_b;
+	
+	reg rx_wr_a_latch;
+	reg rx_first_a=1;
+	always@(posedge clk /*or posedge reset*/) begin
+	
+		if (rx_wr_a) begin
+			rx_wr_a_latch<=1;
+		end
+	
+	
+		wr_data_a<=0;
+		wr_data_b<=0;
 		if (reset) begin
 		  rindex_latch <= 0;
-			data_a <= 0;
+			//data_a <= 0;
-			data_b <= 0;
+			tx_data_a<=0;
+			data_b <= 0;
+			rx_wr_a_latch<=0;
+			wr_data_a<=0;
+			rx_first_a<=1;
 		end else if (cen && cs) begin
 			if (!rs[1]) begin
 				/* Default, reset index */
@@ -153,12 +181,33 @@ module scc
 				  
 					/* Add point high */
 					rindex_latch[3] <= (wdata[5:3] == 3'b001);
+					/* enable int on next rx char */
+					if (wdata[5:3] == 3'b100)
+						rx_first_a<=1;
 				end
 			end else begin
 				if (we) begin
-					if (rs[0]) data_a <= wdata;
+					if (rs[0]) begin 
-					else data_b <= wdata;
+						//data_a <= wdata;
-				end
+						tx_data_a <= wdata;
+						wr_data_a<=1;
+					end
+					else
+						begin
+						data_b <= wdata;
+						wr_data_b<=1;
+						end
+					end
+				else begin
+					// clear the read register?
+					if (rs[0]) begin 
+						rx_wr_a_latch<=0;
+						rx_first_a<=0;
+					end
+					else begin
+					
+					end
+				end
 			end
 		end
 	end
@@ -207,6 +256,37 @@ module scc
 		  wr2 <= wdata;			
 	end
 
+	/* WR3
+	 * Reset: unchanged 
+	 */
+	always@(posedge clk or posedge reset_hw) begin
+		if (reset_hw)
+		  wr3_a <= 0;
+		else if (cen && wreg_a && rindex == 3)
+		  wr3_a <= wdata;
+	end
+	always@(posedge clk or posedge reset_hw) begin
+		if (reset_hw)
+		  wr3_b <= 0;		
+		else if (cen && wreg_b && rindex == 3)
+		  wr3_b <= wdata;
+	end
+	/* WR4
+	 * Reset: unchanged 
+	 */
+	always@(posedge clk or posedge reset_hw) begin
+		if (reset_hw)
+		  wr4_a <= 0;
+		else if (cen && wreg_a && rindex == 4)
+		  wr4_a <= wdata;
+	end
+	always@(posedge clk or posedge reset_hw) begin
+		if (reset_hw)
+		  wr4_b <= 0;		
+		else if (cen && wreg_b && rindex == 4)
+		  wr4_b <= wdata;
+	end
+
 	/* WR5
 	 * Reset: Bits 7,4,3,2,1 to 0
 	 */
@@ -231,6 +311,39 @@ module scc
 		end
 	end
 
+	/* WR8 : write data to serial port -- a or b?
+	 * 
+	 */
+	always@(posedge clk or posedge reset_hw) begin
+		if (reset_hw) begin
+			wr8_a <= 0;
+			wr8_wr_a <= 1'b0;
+		end
+		else if (cen && (rs[1] & we ) && rindex == 8) begin
+			wr8_wr_a <= 1'b1;
+			wr8_a <= wdata;			
+		end
+		else begin
+	          wr8_wr_a <= 1'b0;
+		end
+	end
+
+	always@(posedge clk or posedge reset_hw) begin
+		if (reset_hw) begin
+		  wr8_b <= 0;
+	          wr8_wr_b <= 1'b0;
+		end
+		else if (cen && (wreg_b ) && rindex == 8)
+		begin
+	          wr8_wr_b <= 1'b1;
+		  wr8_b <= wdata;			
+		end
+		else
+		begin
+	          wr8_wr_b <= 1'b0;
+		end
+	end
+	
 	/* WR9. Special: top bits are reset, handled separately, bottom
 	 * bits are only reset by a hw reset
 	 */
@@ -378,12 +491,13 @@ module scc
 	/* RR0 */
 	assign rr0_a = { 1'b0, /* Break */
 			 1'b1, /* Tx Underrun/EOM */
-			 1'b0, /* CTS */
+			 wr15_a[5] ? cts_latch_a : cts_a, /* CTS */
 			 1'b0, /* Sync/Hunt */
 			 wr15_a[3] ? dcd_latch_a : dcd_a, /* DCD */
-			 1'b1, /* Tx Empty */
+			 //1'b1, /*TX EMPTY */
+			 ~tx_busy_a, /* Tx Empty */
 			 1'b0, /* Zero Count */
-			 1'b0  /* Rx Available */
+			 rx_wr_a_latch  /* Rx Available */
 			 };
 	assign rr0_b = { 1'b0, /* Break */
 			 1'b1, /* Tx Underrun/EOM */
@@ -397,13 +511,13 @@ module scc
 
 	/* RR1 */
 	assign rr1_a = { 1'b0, /* End of frame */
-			 1'b0, /* CRC/Framing error */
+			 1'b0,//frame_err_a, /* CRC/Framing error */
 			 1'b0, /* Rx Overrun error */
-			 1'b0, /* Parity error */
+			 1'b0,//parity_err_a, /* Parity error */
 			 1'b0, /* Residue code 0 */
 			 1'b1, /* Residue code 1 */
 			 1'b1, /* Residue code 2 */
-			 1'b1  /* All sent */
+			 ~tx_busy_a  /* All sent */
 			 };
 	
 	assign rr1_b = { 1'b0, /* End of frame */
@@ -483,15 +597,110 @@ module scc
 	 *
 	 * Need to add latches. Tx irq is latched when buffer goes from full->empty,
 	 * it's not a permanent state. For now keep it clear. Will have to fix that.
+	* TODO: AJS - look at tx and interrupt logic
 	 */
-	assign rx_irq_pend_a = 0;
+	 
-	assign tx_irq_pend_a = 0 /*& wr1_a[1]*/; /* Tx always empty for now */
+	 /*
-	assign ex_irq_pend_a = ex_irq_ip_a;
+	 The TxIP is reset either by writing data to the transmit buffer or by issuing the Reset Tx Int command in WR0
+	 */
+
+reg tx_fin_pre;
+reg tx_ip;
+reg tx_mip;
+
+/*
+reg tx_ie;
+always @(posedge clk) begin
+	if (reset_a|reset_hw|reset)
+		tx_ie<=0;
+	else if (wreg_a & (rindex == 1) )
+		tx_ie<=wdata[1];
+end
+*/
+
+always @(posedge clk) begin
+	if (reset) begin
+      tx_ip<=0;
+      tx_mip<=0;
+	end
+	else begin
+      tx_fin_pre<=tx_busy_a;
+		 
+		if (wr5_a[3] &  wr1_a[1] & tx_busy_a & ~tx_fin_pre) begin
+			tx_ip<=~tx_mip;
+			tx_mip<=0;
+		end
+		if (wreg_a & (rindex == 0) & (wdata[5:3] == 3'b111)) begin
+			tx_ip<=0;
+		end
+		if (wreg_a & (rindex == 0) & (wdata[5:3] == 3'b101)) begin
+          // If CIP=1, inhibit generation of next TX interrupt
+          // Actually, "Reset TxInt pend." clears current interrupt
+          tx_mip<= ~tx_ip;
+          tx_ip<=0;
+		end
+		if (wr5_a[3]==0)begin
+			tx_mip<=0;
+			tx_ip<=0;
+		end
+	end	
+end
+
+
+
+
+
+	 reg tx_busy_a_r;
+	 reg tx_latch_a;
+	 always @(posedge clk) begin
+		tx_busy_a_r <= tx_busy_a;
+		// when we transition from empty to full, we create an interrupt
+		if (reset | reset_hw | reset_a)
+			tx_latch_a<=0;
+		else if  (tx_busy_a_r ==1 && tx_busy_a==0)
+			tx_latch_a<=1;
+		// cleared when we write again
+		else if (wr_data_a)
+			tx_latch_a<=0;
+		// or when we set the reset in wr0
+		else if (wreg_a & (rindex == 0) & (wdata[5:3] == 3'b010))
+			tx_latch_a<=0;
+		//else if (wreg_a & (rindex == 0) & (wdata[5:3] == 3'b111)) // clear highest under service?
+	 end
+
+	 
+	 
+	 wire wreq_n;
+	//assign rx_irq_pend_a =  rx_wr_a_latch & ( (wr1_a[3] &&  ~wr1_a[4])|| (~wr1_a[3] &&  wr1_a[4])) & wr3_a[0];	/* figure out the interrupt on / off */
+	//assign rx_irq_pend_a =  rx_wr_a_latch & ( (wr1_a[3] &  ~wr1_a[4])| (~wr1_a[3] &  wr1_a[4])) & wr3_a[0];	/* figure out the interrupt on / off */
+
+	/* figure out the interrupt on / off */
+	/* rx enable: wr3_a[0] */
+	/* wr1_a  4  3
+	          0  0  = rx int disable
+	          0  1  = rx int on first char or special
+				 1  0  = rx int on all rx chars or special
+				 1  1  = rx int on special cond only
+	*/
+	//                       rx enable   char waiting        01,10 only             first char    
+	assign rx_irq_pend_a =   wr3_a[0] & rx_wr_a_latch & (wr1_a[3] ^ wr1_a[4]) & ((wr1_a[3] & rx_first_a )|(wr1_a[4]));
+
+//	assign tx_irq_pend_a = 0;
+//	assign tx_irq_pend_a = tx_busy_a & wr1_a[1];
+
+	assign tx_irq_pend_a = tx_ip;
+//assign tx_irq_pend_a =  wr1_a[1]; /* Tx always empty for now */
+
+   wire cts_interrupt = wr1_a[0] &&  wr15_a[5] || (tx_busy_a_r ==1 && tx_busy_a==0) || (tx_busy_a_r ==0 && tx_busy_a==1);/* if cts changes */
+
+	assign ex_irq_pend_a = ex_irq_ip_a ; 
 	assign rx_irq_pend_b = 0;
 	assign tx_irq_pend_b = 0 /*& wr1_b[1]*/; /* Tx always empty for now */
 	assign ex_irq_pend_b = ex_irq_ip_b;
 
 	assign _irq = ~(wr9[3] & (rx_irq_pend_a |
+				  
+				  
 				  rx_irq_pend_b |
 				  tx_irq_pend_a |
 				  tx_irq_pend_b |
@@ -514,12 +723,13 @@ module scc
 	 * corresponding interrupt is enabled in WR15
 	 */
 	assign dcd_ip_a = (dcd_a != dcd_latch_a) & wr15_a[3];
+	assign cts_ip_a = (cts_a != cts_latch_a) & wr15_a[5];
 	assign dcd_ip_b = (dcd_b != dcd_latch_b) & wr15_b[3];
 
 	/* Latches close when an enabled IP bit is set and latches
 	 * are currently open
 	 */
-	assign do_latch_a = latch_open_a & (dcd_ip_a /* | cts... */);
+	assign do_latch_a = latch_open_a & (dcd_ip_a | cts_ip_a  /* | cts... */);
 	assign do_latch_b = latch_open_b & (dcd_ip_b /* | cts... */);
 
 	/* "Master" interrupt, set when latch close & WR1[0] is set */
@@ -570,10 +780,12 @@ module scc
 	always@(posedge clk or posedge reset) begin
 		if (reset) begin
 			dcd_latch_a <= 0;
+			cts_latch_a <= 0;
 			/* cts ... */
 		end else if(cep) begin
 			if (do_latch_a)
 			  dcd_latch_a <= dcd_a;
+			  cts_latch_a <= cts_a;
 			/* cts ... */
 		end
 	end
@@ -587,10 +799,151 @@ module scc
 			/* cts ... */
 		end
 	end
+	
+
 
 	/* NYI */
-	assign txd = 1;
+//	assign txd = 1;
-	assign rts = 1;
+//	assign rts = 1;
 
-	assign wreq = 1;	
+	/* UART */
+
+//wr_3_a
+//wr_3_b
+// bit 
+wire parity_ena_a= wr4_a[0];
+wire parity_even_a= wr4_a[1];
+reg [1:0] stop_bits_a= 2'b00;
+reg [1:0] bit_per_char_a = 2'b00;
+/*
+76543210
+data>>2 & 3
+wr4_a[3:2] 
+case(wr4_a[3:2])
+2'b00:
+// sync mode enable
+2'b01:
+// 1 stop bit
+	stop_bits_a <= 2'b0;
+2'b10:
+// 1.5 stop bit
+	stop_bits_a <= 2'b0;
+2'b11:
+// 2 stop bit
+	stop_bits_a <= 2'b1;
+default:
+	stop_bits_a <= 2'b0;
+endcase
+
+*/
+/*
+76543210
+^__ 76 
+wr_3_a[7:6]  -- bits per char
+
+                case (wr_3_a[7:6]})
+                        2'b00:  // 5
+				bit_per_char_a  <= 2'b11;
+                        2'b01:  // 7
+				bit_per_char_a  <= 2'b01;
+                        2'b10:  // 6 
+				bit_per_char_a  <= 2'b10;
+                        2'b11:  // 8
+				bit_per_char_a  <= 2'b00;
+		endcase
+*/
+/*
+300 -- 62.668800 /  =  208896
+600 -- 62.668800 /  =  104448
+1200-- 62.668800 /  =  69632
+2400 -- 62.668800 / 2400 = 26112
+4800 -- 62.668800 / 4800  = 13056
+9600 -- 62.668800 / 9600 = 6528
+1440 -- 62.668800 / 14400 = 4352
+19200 -- 62.668800 /  19200= 3264
+38400 -- 62.668800 / 28800 =  2176
+38400 -- 62.668800 / 38400 =  1632
+57600 -- 62.668800 / 57600 = 1088
+115200 -- 62.668800 / 115200 = 544
+230400 -- 62.668800 / 230400 = 272
+
+
+32.5 / 115200 = 
+
+*/
+// case the baud rate based on wr12_a and 13_a
+// wr_12_a  -- contains the baud rate lower byte
+// wr_13_a  -- contains the baud rate high byte
+/*
+        always @(posedge clk) begin
+                case ({wr13_a,wr12_a})
+                        16'd380:  // 300 baud
+                                baud_divid_speed_a <= 24'd108333;
+                        16'd94:  // 1200 baud
+                                baud_divid_speed_a <= 24'd27083;
+                        16'd46:  // 2400 baud
+                                baud_divid_speed_a <= 24'd13542;
+                        16'd22:  // 4800 baud
+                                baud_divid_speed_a <= 24'd6770;
+                        16'd10:  // 9600 baud
+                                baud_divid_speed_a <= 24'd3385;
+                        16'd6:  // 14400 baud
+                                baud_divid_speed_a <= 24'd2257;
+                        16'd4:  // 19200 baud
+                                baud_divid_speed_a <= 24'd1693;
+                        16'd2:  // 28800 baud
+                                baud_divid_speed_a <= 24'd1128;
+                        16'd1:  // 38400 baud
+                                baud_divid_speed_a <= 24'd846;
+                        16'd0:  // 57600 baud
+                                baud_divid_speed_a <= 24'd564;
+                        default: 
+                                baud_divid_speed_a <= 24'd282;
+                endcase
+        end
+
+*/
+
+
+
+//reg [23:0] baud_divid_speed_a = 24'd1088;
+//reg [23:0] baud_divid_speed_a = 24'd544;
+reg [23:0] baud_divid_speed_a = 24'd282;
+//reg [23:0] baud_divid_speed_a = 24'd564;
+wire tx_busy_a;
+wire rx_wr_a;
+wire [30:0] uart_setup_rx_a = { 1'b0, bit_per_char_a, 1'b0, parity_ena_a, 1'b0, parity_even_a, baud_divid_speed_a  } ;
+wire [30:0] uart_setup_tx_a = { 1'b0, bit_per_char_a, 1'b0, parity_ena_a, 1'b0, parity_even_a, baud_divid_speed_a  } ;
+//wire [30:0] uart_setup_rx_a = { 1'b0, 1'b0, 1'b0, 1'b0, 1'b0, 1'b0, baud_divid_speed_a  } ;
+//wire [30:0] uart_setup_tx_a = { 1'b0, 1'b0, 1'b0, 1'b0, 1'b0, 1'b0, baud_divid_speed_a  } ;
+rxuart rxuart_a (
+	.i_clk(clk), 
+	.i_reset(reset_a|reset_hw), 
+	.i_setup(uart_setup_rx_a), 
+	.i_uart_rx(rxd), 
+	.o_wr(rx_wr_a), // TODO -- check on this flag
+	.o_data(data_a),   // TODO we need to save this off only if wreq is set, and mux it into data_a in the right spot
+	.o_break(break_a),
+	.o_parity_err(parity_err_a), 
+	.o_frame_err(frame_err_a), 
+	.o_ck_uart()
+	);
+txuart txuart_a
+	(
+	.i_clk(clk), 
+	.i_reset(reset_a|reset_hw), 
+	.i_setup(uart_setup_tx_a), 
+	.i_break(1'b0), 
+	.i_wr(wr_data_a),   // TODO -- we need to send data when we get the register command i guess???
+	.i_data(tx_data_a),
+	//.i_cts_n(~cts), 
+	.i_cts_n(1'b0), 
+	.o_uart_tx(txd), 
+	.o_busy(tx_busy_a)); // TODO -- do we need this busy line?? probably 
+
+	wire cts_a = ~tx_busy_a;
+	
+	// RTS and CTS are active low
+	assign rts = rx_wr_a_latch;
+	assign wreq=1;
 endmodule

rtl/uart/rxuart.v

@@ -0,0 +1,467 @@
+////////////////////////////////////////////////////////////////////////////////
+//
+// Filename: 	rxuart.v
+//
+// Project:	wbuart32, a full featured UART with simulator
+//
+// Purpose:	Receive and decode inputs from a single UART line.
+//
+//
+//	To interface with this module, connect it to your system clock,
+//	pass it the 32 bit setup register (defined below) and the UART
+//	input.  When data becomes available, the o_wr line will be asserted
+//	for one clock cycle.  On parity or frame errors, the o_parity_err
+//	or o_frame_err lines will be asserted.  Likewise, on a break 
+//	condition, o_break will be asserted.  These lines are self clearing.
+//
+//	There is a synchronous reset line, logic high.
+//
+//	Now for the setup register.  The register is 32 bits, so that this
+//	UART may be set up over a 32-bit bus.
+//
+//	i_setup[30]	True if we are not using hardware flow control.  This bit
+//		is ignored within this module, as any receive hardware flow
+//		control will need to be implemented elsewhere.
+//
+//	i_setup[29:28]	Indicates the number of data bits per word.  This will
+//		either be 2'b00 for an 8-bit word, 2'b01 for a 7-bit word, 2'b10
+//		for a six bit word, or 2'b11 for a five bit word.
+//
+//	i_setup[27]	Indicates whether or not to use one or two stop bits.
+//		Set this to one to expect two stop bits, zero for one.
+//
+//	i_setup[26]	Indicates whether or not a parity bit exists.  Set this
+//		to 1'b1 to include parity.
+//
+//	i_setup[25]	Indicates whether or not the parity bit is fixed.  Set
+//		to 1'b1 to include a fixed bit of parity, 1'b0 to allow the
+//		parity to be set based upon data.  (Both assume the parity
+//		enable value is set.)
+//
+//	i_setup[24]	This bit is ignored if parity is not used.  Otherwise,
+//		in the case of a fixed parity bit, this bit indicates whether
+//		mark (1'b1) or space (1'b0) parity is used.  Likewise if the
+//		parity is not fixed, a 1'b1 selects even parity, and 1'b0
+//		selects odd.
+//
+//	i_setup[23:0]	Indicates the speed of the UART in terms of clocks.
+//		So, for example, if you have a 200 MHz clock and wish to
+//		run your UART at 9600 baud, you would take 200 MHz and divide
+//		by 9600 to set this value to 24'd20834.  Likewise if you wished
+//		to run this serial port at 115200 baud from a 200 MHz clock,
+//		you would set the value to 24'd1736
+//
+//	Thus, to set the UART for the common setting of an 8-bit word, 
+//	one stop bit, no parity, and 115200 baud over a 200 MHz clock, you
+//	would want to set the setup value to:
+//
+//	32'h0006c8		// For 115,200 baud, 8 bit, no parity
+//	32'h005161		// For 9600 baud, 8 bit, no parity
+//	
+//
+//
+// Creator:	Dan Gisselquist, Ph.D.
+//		Gisselquist Technology, LLC
+//
+////////////////////////////////////////////////////////////////////////////////
+//
+// Copyright (C) 2015-2019, 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
+// <http://www.gnu.org/licenses/> for a copy.
+//
+// License:	GPL, v3, as defined and found on www.gnu.org,
+//		http://www.gnu.org/licenses/gpl.html
+//
+//
+////////////////////////////////////////////////////////////////////////////////
+//
+//
+`default_nettype	none
+//
+// States: (@ baud counter == 0)
+//	0	First bit arrives
+//	..7	Bits arrive
+//	8	Stop bit (x1)
+//	9	Stop bit (x2)
+//	c	break condition
+//	d	Waiting for the channel to go high
+//	e	Waiting for the reset to complete
+//	f	Idle state
+`define	RXU_BIT_ZERO		4'h0
+`define	RXU_BIT_ONE		4'h1
+`define	RXU_BIT_TWO		4'h2
+`define	RXU_BIT_THREE		4'h3
+`define	RXU_BIT_FOUR		4'h4
+`define	RXU_BIT_FIVE		4'h5
+`define	RXU_BIT_SIX		4'h6
+`define	RXU_BIT_SEVEN		4'h7
+`define	RXU_PARITY		4'h8
+`define	RXU_STOP		4'h9
+`define	RXU_SECOND_STOP		4'ha
+// Unused 4'hb
+// Unused 4'hc
+`define	RXU_BREAK		4'hd
+`define	RXU_RESET_IDLE		4'he
+`define	RXU_IDLE		4'hf
+
+module rxuart(i_clk, i_reset, i_setup, i_uart_rx, o_wr, o_data, o_break,
+			o_parity_err, o_frame_err, o_ck_uart);
+	parameter [30:0] INITIAL_SETUP = 31'd868;
+	// 8 data bits, no parity, (at least 1) stop bit
+	input	wire		i_clk, i_reset;
+	/* verilator lint_off UNUSED */
+	input	wire	[30:0]	i_setup;
+	/* verilator lint_on UNUSED */
+	input	wire		i_uart_rx;
+	output	reg		o_wr;
+	output	reg	[7:0]	o_data;
+	output	reg		o_break;
+	output	reg		o_parity_err, o_frame_err;
+	output	wire		o_ck_uart;
+
+
+	wire	[27:0]	clocks_per_baud, break_condition, half_baud;
+	wire	[1:0]	data_bits;
+	wire		use_parity, parity_even, dblstop, fixd_parity;
+	reg	[29:0]	r_setup;
+	reg	[3:0]	state;
+
+	assign	clocks_per_baud = { 4'h0, r_setup[23:0] };
+	// assign hw_flow_control = !r_setup[30];
+	assign	data_bits   = r_setup[29:28];
+	assign	dblstop     = r_setup[27];
+	assign	use_parity  = r_setup[26];
+	assign	fixd_parity = r_setup[25];
+	assign	parity_even = r_setup[24];
+	assign	break_condition = { r_setup[23:0], 4'h0 };
+	assign	half_baud = { 5'h00, r_setup[23:1] }-28'h1;
+	reg	[27:0]	baud_counter;
+	reg		zero_baud_counter;
+
+
+	// Since this is an asynchronous receiver, we need to register our
+	// input a couple of clocks over to avoid any problems with 
+	// metastability.  We do that here, and then ignore all but the
+	// ck_uart wire.
+	reg	q_uart, qq_uart, ck_uart;
+	initial	q_uart  = 1'b0;
+	initial	qq_uart = 1'b0;
+	initial	ck_uart = 1'b0;
+	always @(posedge i_clk)
+	begin
+		q_uart <= i_uart_rx;
+		qq_uart <= q_uart;
+		ck_uart <= qq_uart;
+	end
+
+	// In case anyone else wants this clocked, stabilized value, we
+	// offer it on our output.
+	assign	o_ck_uart = ck_uart;
+
+	// Keep track of the number of clocks since the last change.
+	//
+	// This is used to determine if we are in either a break or an idle
+	// condition, as discussed further below.
+	reg	[27:0]	chg_counter;
+	initial	chg_counter = 28'h00;
+	always @(posedge i_clk)
+		if (i_reset)
+			chg_counter <= 28'h00;
+		else if (qq_uart != ck_uart)
+			chg_counter <= 28'h00;
+		else if (chg_counter < break_condition)
+			chg_counter <= chg_counter + 1;
+
+	// Are we in a break condition?
+	//
+	// A break condition exists if the line is held low for longer than
+	// a data word.  Hence, we keep track of when the last change occurred.
+	// If it was more than break_condition clocks ago, and the current input
+	// value is a 0, then we're in a break--and nothing can be read until
+	// the line idles again.
+	initial	o_break    = 1'b0;
+	always @(posedge i_clk)
+		o_break <= ((chg_counter >= break_condition)&&(~ck_uart))? 1'b1:1'b0;
+
+	// Are we between characters?
+	//
+	// The opposite of a break condition is where the line is held high
+	// for more clocks than would be in a character.  When this happens,
+	// we know we have synchronization--otherwise, we might be sampling
+	// from within a data word.
+	//
+	// This logic is used later to hold the RXUART in a reset condition
+	// until we know we are between data words.  At that point, we should
+	// be able to hold on to our synchronization.
+	reg	line_synch;
+	initial	line_synch = 1'b0;
+	always @(posedge i_clk)
+		line_synch <= ((chg_counter >= break_condition)&&(ck_uart));
+
+	// Are we in the middle of a baud iterval?  Specifically, are we
+	// in the middle of a start bit?  Set this to high if so.  We'll use
+	// this within our state machine to transition out of the IDLE
+	// state.
+	reg	half_baud_time;
+	initial	half_baud_time = 0;
+	always @(posedge i_clk)
+		half_baud_time <= (~ck_uart)&&(chg_counter >= half_baud);
+
+
+	// Allow our controlling processor to change our setup at any time
+	// outside of receiving/processing a character.
+	initial	r_setup     = INITIAL_SETUP[29:0];
+	always @(posedge i_clk)
+		if (state >= `RXU_RESET_IDLE)
+			r_setup <= i_setup[29:0];
+
+
+	// Our monster state machine.  YIKES!
+	//
+	// Yeah, this may be more complicated than it needs to be.  The basic
+	// progression is:
+	//	RESET -> RESET_IDLE -> (when line is idle) -> IDLE
+	//	IDLE -> bit 0 -> bit 1 -> bit_{ndatabits} -> 
+	//		(optional) PARITY -> STOP -> (optional) SECOND_STOP
+	//		-> IDLE
+	//	ANY -> (on break) BREAK -> IDLE
+	//
+	// There are 16 states, although all are not used.  These are listed
+	// at the top of this file.
+	//
+	//	Logic inputs (12):	(I've tried to minimize this number)
+	//		state	(4)
+	//		i_reset
+	//		line_synch
+	//		o_break
+	//		ckuart
+	//		half_baud_time
+	//		zero_baud_counter
+	//		use_parity
+	//		dblstop
+	//	Logic outputs (4):
+	//		state
+	//
+	initial	state = `RXU_RESET_IDLE;
+	always @(posedge i_clk)
+	begin
+		if (i_reset)
+			state <= `RXU_RESET_IDLE;
+		else if (state == `RXU_RESET_IDLE)
+		begin
+			if (line_synch)
+				// Goto idle state from a reset
+				state <= `RXU_IDLE;
+			else // Otherwise, stay in this condition 'til reset
+				state <= `RXU_RESET_IDLE;
+		end else if (o_break)
+		begin // We are in a break condition
+			state <= `RXU_BREAK;
+		end else if (state == `RXU_BREAK)
+		begin // Goto idle state following return ck_uart going high
+			if (ck_uart)
+				state <= `RXU_IDLE;
+			else
+				state <= `RXU_BREAK;
+		end else if (state == `RXU_IDLE)
+		begin // Idle state, independent of baud counter
+			if ((~ck_uart)&&(half_baud_time))
+			begin
+				// We are in the center of a valid start bit
+				case (data_bits)
+				2'b00: state <= `RXU_BIT_ZERO;
+				2'b01: state <= `RXU_BIT_ONE;
+				2'b10: state <= `RXU_BIT_TWO;
+				2'b11: state <= `RXU_BIT_THREE;
+				endcase
+			end else // Otherwise, just stay here in idle
+				state <= `RXU_IDLE;
+		end else if (zero_baud_counter)
+		begin
+			if (state < `RXU_BIT_SEVEN)
+				// Data arrives least significant bit first.
+				// By the time this is clocked in, it's what
+				// you'll have.
+				state <= state + 1;
+			else if (state == `RXU_BIT_SEVEN)
+				state <= (use_parity) ? `RXU_PARITY:`RXU_STOP;
+			else if (state == `RXU_PARITY)
+				state <= `RXU_STOP;
+			else if (state == `RXU_STOP)
+			begin // Stop (or parity) bit(s)
+				if (~ck_uart) // On frame error, wait 4 ch idle
+					state <= `RXU_RESET_IDLE;
+				else if (dblstop)
+					state <= `RXU_SECOND_STOP;
+				else
+					state <= `RXU_IDLE;
+			end else // state must equal RX_SECOND_STOP
+			begin
+				if (~ck_uart) // On frame error, wait 4 ch idle
+					state <= `RXU_RESET_IDLE;
+				else
+					state <= `RXU_IDLE;
+			end
+		end
+	end
+
+	// Data bit capture logic.
+	//
+	// This is drastically simplified from the state machine above, based
+	// upon: 1) it doesn't matter what it is until the end of a captured
+	// byte, and 2) the data register will flush itself of any invalid
+	// data in all other cases.  Hence, let's keep it real simple.
+	// The only trick, though, is that if we have parity, then the data
+	// register needs to be held through that state without getting
+	// updated.
+	reg	[7:0]	data_reg;
+	always @(posedge i_clk)
+		if ((zero_baud_counter)&&(state != `RXU_PARITY))
+			data_reg <= { ck_uart, data_reg[7:1] };
+
+	// Parity calculation logic
+	//
+	// As with the data capture logic, all that must be known about this
+	// bit is that it is the exclusive-OR of all bits prior.  The first
+	// of those will follow idle, so we set ourselves to zero on idle.
+	// Then, as we walk through the states of a bit, all will adjust this
+	// value up until the parity bit, where the value will be read.  Setting
+	// it then or after will be irrelevant, so ... this should be good
+	// and simplified.  Note--we don't need to adjust this on reset either,
+	// since the reset state will lead to the idle state where we'll be
+	// reset before any transmission takes place.
+	reg		calc_parity;
+	always @(posedge i_clk)
+		if (state == `RXU_IDLE)
+			calc_parity <= 0;
+		else if (zero_baud_counter)
+			calc_parity <= calc_parity ^ ck_uart;
+
+	// Parity error logic
+	//
+	// Set during the parity bit interval, read during the last stop bit
+	// interval, cleared on BREAK, RESET_IDLE, or IDLE states.
+	initial	o_parity_err = 1'b0;
+	always @(posedge i_clk)
+		if ((zero_baud_counter)&&(state == `RXU_PARITY))
+		begin
+			if (fixd_parity)
+				// Fixed parity bit--independent of any dat
+				// value.
+				o_parity_err <= (ck_uart ^ parity_even);
+			else if (parity_even)
+				// Parity even: The XOR of all bits including
+				// the parity bit must be zero.
+				o_parity_err <= (calc_parity != ck_uart);
+			else
+				// Parity odd: the parity bit must equal the
+				// XOR of all the data bits.
+				o_parity_err <= (calc_parity == ck_uart);
+		end else if (state >= `RXU_BREAK)
+			o_parity_err <= 1'b0;
+
+	// Frame error determination
+	//
+	// For the purpose of this controller, a frame error is defined as a
+	// stop bit (or second stop bit, if so enabled) not being high midway
+	// through the stop baud interval.   The frame error value is
+	// immediately read, so we can clear it under all other circumstances.
+	// Specifically, we want it clear in RXU_BREAK, RXU_RESET_IDLE, and
+	// most importantly in RXU_IDLE.
+	initial	o_frame_err  = 1'b0;
+	always @(posedge i_clk)
+		if ((zero_baud_counter)&&((state == `RXU_STOP)
+						||(state == `RXU_SECOND_STOP)))
+			o_frame_err <= (o_frame_err)||(~ck_uart);
+		else if ((zero_baud_counter)||(state >= `RXU_BREAK))
+			o_frame_err <= 1'b0;
+
+	// Our data bit logic doesn't need nearly the complexity of all that
+	// work above.  Indeed, we only need to know if we are at the end of
+	// a stop bit, in which case we copy the data_reg into our output
+	// data register, o_data.
+	//
+	// We would also set o_wr to be true when this is the case, but ... we
+	// won't know if there is a frame error on the second stop bit for 
+	// another baud interval yet.  So, instead, we set up the logic so that
+	// we know on the next zero baud counter that we can write out.  That's
+	// the purpose of pre_wr.
+	initial	o_data = 8'h00;
+	reg	pre_wr;
+	initial	pre_wr = 1'b0;
+	always @(posedge i_clk)
+		if (i_reset)
+		begin
+			pre_wr <= 1'b0;
+			o_data <= 8'h00;
+		end else if ((zero_baud_counter)&&(state == `RXU_STOP))
+		begin
+			pre_wr <= 1'b1;
+			case (data_bits)
+			2'b00: o_data <= data_reg;
+			2'b01: o_data <= { 1'b0, data_reg[7:1] };
+			2'b10: o_data <= { 2'b0, data_reg[7:2] };
+			2'b11: o_data <= { 3'b0, data_reg[7:3] };
+			endcase
+		end else if ((zero_baud_counter)||(state == `RXU_IDLE))
+			pre_wr <= 1'b0;
+
+	// Create an output strobe, true for one clock only, once we know
+	// all we need to know.  o_data will be set on the last baud interval,
+	// o_parity_err on the last parity baud interval (if it existed,
+	// cleared otherwise, so ... we should be good to go here.)
+	initial	o_wr   = 1'b0;
+	always @(posedge i_clk)
+		if ((zero_baud_counter)||(state == `RXU_IDLE))
+			o_wr <= (pre_wr)&&(!i_reset);
+		else
+			o_wr <= 1'b0;
+
+	// The baud counter
+	//
+	// This is used as a "clock divider" if you will, but the clock needs
+	// to be reset before any byte can be decoded.  In all other respects,
+	// we set ourselves up for clocks_per_baud counts between baud
+	// intervals.
+	always @(posedge i_clk)
+		if (i_reset)
+			baud_counter <= clocks_per_baud-28'h01;
+		else if (zero_baud_counter)
+			baud_counter <= clocks_per_baud-28'h01;
+		else case(state)
+			`RXU_RESET_IDLE:baud_counter <= clocks_per_baud-28'h01;
+			`RXU_BREAK:	baud_counter <= clocks_per_baud-28'h01;
+			`RXU_IDLE:	baud_counter <= clocks_per_baud-28'h01;
+			default:	baud_counter <= baud_counter-28'h01;
+		endcase
+
+	// zero_baud_counter
+	//
+	// Rather than testing whether or not (baud_counter == 0) within our
+	// (already too complicated) state transition tables, we use
+	// zero_baud_counter to pre-charge that test on the clock
+	// before--cleaning up some otherwise difficult timing dependencies.
+	initial	zero_baud_counter = 1'b0;
+	always @(posedge i_clk)
+		if (state == `RXU_IDLE)
+			zero_baud_counter <= 1'b0;
+		else
+		zero_baud_counter <= (baud_counter == 28'h01);
+
+
+endmodule
+
+