From 4f760de4d917c0484772bb0cc3a192797db4b529 Mon Sep 17 00:00:00 2001
From: harbaum <till@harbaum.org>
Date: Thu, 27 Feb 2014 20:17:51 +0000
Subject: [PATCH] Printer redirection via USB

---
 cores/mist/mist_top.v | 62 +++++++++++++++++++++++++++++++++++++++----
 cores/mist/user_io.v  | 19 +++++++++++++
 2 files changed, 76 insertions(+), 5 deletions(-)

diff --git a/cores/mist/mist_top.v b/cores/mist/mist_top.v
index 28d6344..1c5a84b 100644
--- a/cores/mist/mist_top.v
+++ b/cores/mist/mist_top.v
@@ -287,10 +287,10 @@ wire ste_dma_snd_xsirq, ste_dma_snd_xsirq_delayed;
 // mfp io7 is mono_detect which in ste is xor'd with the dma sound irq
 wire mfp_io7 = system_ctrl[8] ^ (ste?ste_dma_snd_xsirq:1'b0);
 
-// input 0 is busy from printer port which has a pullup
+// input 0 is busy from printer which is pulled up when the printer cannot accept further data
 // inputs 1,2 and 6 are inputs from serial which have pullups before an inverter
-wire [7:0] mfp_gpio_in = {mfp_io7, 1'b0, !dma_irq, !acia_irq, !blitter_irq, 3'b001 };
-wire [1:0] mfp_timer_in = {st_de, ste?ste_dma_snd_xsirq_delayed:1'b1};
+wire [7:0] mfp_gpio_in = {mfp_io7, 1'b0, !dma_irq, !acia_irq, !blitter_irq, 2'b00, parallal_fifo_full};
+wire [1:0] mfp_timer_in = {st_de, ste?ste_dma_snd_xsirq_delayed:parallal_fifo_full};
 
 mfp mfp (
 	// cpu register interface
@@ -457,11 +457,53 @@ sigma_delta_dac sigma_delta_dac_r (
 );
 
 //// ym2149 sound chip ////
+
+// ------ fifo to store printer data coming from psg ---------
+localparam FIFO_ADDR_BITS = 4;
+localparam FIFO_DEPTH = (1 << FIFO_ADDR_BITS);
+reg [7:0] fifoOut [FIFO_DEPTH-1:0];
+reg [FIFO_ADDR_BITS-1:0] writePout, readPout;
+
+wire parallal_fifo_full = (readPout === (writePout + 4'd1));
+assign parallel_data_out_available = (readPout != writePout);
+assign parallel_data_out = fifoOut[readPout];
+
+// parallel strobe signal
+reg parallel_strobeD, parallel_strobeD2;
+// strobe signal by io controller when reading from parallel fifo
+reg parallel_strobe_outD, parallel_strobe_outD2;
+
+always @(posedge clk_8) begin
+	// printer strobe generated by core/ST using the PSG
+	parallel_strobeD <= port_a_out[5];
+	parallel_strobeD2 <= parallel_strobeD;
+
+	// fifo read strobe generated by io controller
+	parallel_strobe_outD <= parallel_strobe_out;
+	parallel_strobe_outD2 <= parallel_strobe_outD;
+	
+	if(reset) begin
+		readPout <= 4'd0;
+		writePout <= 4'd0;
+	end else begin
+		// rising edge on fifo read strobe from io controller
+		if(parallel_strobe_outD && !parallel_strobe_outD2)
+			readPout <= readPout + 4'd1;
+			
+		// rising edge on strobe signal coming from psg
+		if(parallel_strobeD && !parallel_strobeD2) begin
+			fifoOut[writePout] <= port_b_out;
+			writePout <= writePout + 4'd1;
+		end
+	end
+end	
+	
 reg [1:0] sclk;
 always @ (posedge clk_8)
 	sclk <= sclk + 2'd1;
 
-wire [7:0] port_a_out;
+wire [7:0] port_a_out /* synthesis keep */;
+wire [7:0] port_b_out /* synthesis keep */;
 assign floppy_side = port_a_out[0];
 assign floppy_sel = port_a_out[2:1];
 
@@ -492,7 +534,7 @@ YM2149 ym2149 (
 
 	// port b
 	.I_IOB               ( 8'd0						),
-	.O_IOB              	(								),
+	.O_IOB              	( port_b_out				),
 	.O_IOB_OE_L         	(								),
   
 	//
@@ -1041,6 +1083,11 @@ wire serial_data_from_mfp_available;
 wire [7:0] serial_data_to_mfp;
 wire serial_strobe_to_mfp;
 
+// connection to transfer parallel data from psg to io controller
+wire [7:0] parallel_data_out;
+wire parallel_strobe_out;
+wire parallel_data_out_available;
+
 //// user io has an extra spi channel outside minimig core ////
 user_io user_io(
 		.SPI_CLK(SPI_SCK),
@@ -1063,6 +1110,11 @@ user_io user_io(
       .serial_strobe_in(serial_strobe_to_mfp),
       .serial_data_in(serial_data_to_mfp),
 		
+		// parallel interface
+      .parallel_strobe_out(parallel_strobe_out),
+      .parallel_data_out(parallel_data_out),
+      .parallel_data_out_available(parallel_data_out_available),
+
 		.CORE_TYPE(8'ha3)    // mist core id
 );
 
diff --git a/cores/mist/user_io.v b/cores/mist/user_io.v
index bb7b4d7..e919fed 100644
--- a/cores/mist/user_io.v
+++ b/cores/mist/user_io.v
@@ -23,6 +23,11 @@ module user_io(
 		output reg       serial_strobe_in,
 		output reg [7:0] serial_data_in,
 
+		// parallel data from psg/ym to io controller
+		output reg       parallel_strobe_out,
+		input            parallel_data_out_available,
+		input [7:0]      parallel_data_out,
+
 		output [1:0] 	  BUTTONS,
 		output [1:0]     SWITCHES
 	   );
@@ -55,6 +60,14 @@ module user_io(
 				else
 					SPI_MISO <= serial_data_out[15-cnt];
 			end
+			
+			// parallel psg/ym->io controller
+			if(cmd == 6) begin
+				if(!toggle)
+					SPI_MISO <= parallel_data_out_available;
+				else
+					SPI_MISO <= parallel_data_out[15-cnt];
+			end
 		end
 	end
 		
@@ -65,6 +78,7 @@ module user_io(
 		  ikbd_strobe_in <= 1'b0;
 		  ikbd_strobe_out <= 1'b0;
 		  serial_strobe_out <= 1'b0;
+		  parallel_strobe_out <= 1'b0;
 		end else begin
 			sbuf[6:1] <= sbuf[5:0];
 			sbuf[0] <= SPI_MOSI;
@@ -88,6 +102,7 @@ module user_io(
 				ikbd_strobe_out <= 1'b0;
 				serial_strobe_in <= 1'b0;
 				serial_strobe_out <= 1'b0;
+				parallel_strobe_out <= 1'b0;
 			end
 			
 			// payload byte
@@ -116,6 +131,10 @@ module user_io(
 				// give strobe after second serial byte (toggle ==1)
 			   if((cmd == 5) && toggle)
 					 serial_strobe_out <= 1'b1;
+					 
+				// give strobe after second parallel byte (toggle ==1)
+			   if((cmd == 6) && toggle)
+					 parallel_strobe_out <= 1'b1;
 			end
 		end
 	end