From fd003c7a793fb17fb6dc7ba52873b883b28a578b Mon Sep 17 00:00:00 2001
From: Joshua Wise <joshua@rebirth.joshuawise.com>
Date: Sat, 24 Jan 2009 05:08:28 -0500
Subject: [PATCH] System, Terminal: Provide real-world outputs on non-Verilator
 to avoid optimizing the whole system to nothing.

---
 Terminal.v | 20 +++++++++++++++++++-
 system.v   | 17 +++++++++++++++--
 2 files changed, 34 insertions(+), 3 deletions(-)

diff --git a/Terminal.v b/Terminal.v
index dd041d0..9ddd5d3 100644
--- a/Terminal.v
+++ b/Terminal.v
@@ -7,7 +7,14 @@ module Terminal(
 	output reg cp_busy,
 	input cp_rnw,
 	output reg [31:0] cp_read = 0,
-	input [31:0] cp_write);
+	input [31:0] cp_write
+`ifdef verilator
+`else
+	, output reg [8:0] sys_odata = 0,
+	input [8:0] sys_idata,
+	output reg sys_tookdata = 0
+`endif
+);
 	
 	/* Terminal pretends to be cp5. */
 	reg towrite = 0;
@@ -41,5 +48,16 @@ module Terminal(
 			$c("{extern void term_output(unsigned char d); term_output(",data,");}");
 		else if (didread || !indata[8])
 			indata = $c("({extern unsigned int term_input(); term_input();})");
+`else
+	always @(posedge clk)
+	begin
+		sys_odata = {towrite,data};
+		if (didread || !indata[8])
+		begin
+			indata = sys_idata;
+			sys_tookdata = 1;
+		end else
+			sys_tookdata = 0;
+	end
 `endif
 endmodule
diff --git a/system.v b/system.v
index 07adfd8..f134ffc 100644
--- a/system.v
+++ b/system.v
@@ -1,7 +1,15 @@
 `define BUS_ICACHE 1
 `define BUS_DCACHE 0
 
-module System(input clk);
+module System(input clk
+`ifdef verilator
+`else
+	, output wire [8:0] sys_odata,
+	input [8:0] sys_idata,
+	output wire sys_tookdata
+`endif
+	);
+	
 	wire [7:0] bus_req;
 	wire [7:0] bus_ack;
 	wire [31:0] bus_addr;
@@ -208,7 +216,12 @@ module System(input clk);
 	Terminal terminal(	
 		.clk(clk),
 		.cp_req(cp_req), .cp_insn(cp_insn), .cp_ack(cp_ack_terminal), .cp_busy(cp_busy_terminal), .cp_rnw(cp_rnw),
-		.cp_read(cp_read_terminal), .cp_write(cp_write));
+		.cp_read(cp_read_terminal), .cp_write(cp_write)
+`ifdef verilator
+`else
+		, .sys_odata(sys_odata), .sys_tookdata(sys_tookdata), .sys_idata(sys_idata)
+`endif
+		);
 	
 	Writeback writeback(
 		.clk(clk),
-- 
2.39.2