From: Joshua Wise <joshua@rebirth.joshuawise.com>
Date: Fri, 4 Apr 2008 07:55:37 +0000 (-0400)
Subject: First cut at timer
X-Git-Url: http://git.joshuawise.com/fpgaboy.git/commitdiff_plain/06ad3a30038ac8ca45dd7b0c34213c0c8335c17c

First cut at timer
---

diff --git a/FPGABoy.ise b/FPGABoy.ise
index b37a4cd..a4399b8 100644
Binary files a/FPGABoy.ise and b/FPGABoy.ise differ
diff --git a/Interrupt.v b/Interrupt.v
new file mode 100644
index 0000000..4e3d17d
--- /dev/null
+++ b/Interrupt.v
@@ -0,0 +1,50 @@
+`define ADDR_IF 16'hFF0F
+`define ADDR_IE 16'hFFFF
+
+module Interrupt(
+	input clk,
+	input rd,
+	input wr,
+	input [15:0] addr,
+	inout [7:0] data,
+	input vblank,
+	input lcdc,
+	input tovf,
+	input serial,
+	input buttons,
+	output master,
+	output [7:0] jaddr);
+
+	wire [7:0] iflag = {3'b0,buttons,serial,tovf,lcdc,vblank};
+	reg [7:0] imask = 16'hFFFF;
+	reg [7:0] ihold = 0;
+	wire [7:0] imasked = ihold & imask;
+
+	assign data = rd ?
+	                 (addr == `ADDR_IF) ? ihold :
+	                 (addr == `ADDR_IE) ? imask :
+	                 8'bzzzzzzzz :
+		      8'bzzzzzzzz;
+
+	assign master = (imasked) != 0;
+
+	assign jaddr = imasked[0] ? 8'h40 :
+		       imasked[1] ? 8'h48 :
+		       imasked[2] ? 8'h50 :
+		       imasked[3] ? 8'h58 :
+		       imasked[4] ? 8'h60 : 8'h00;
+
+	always @ (negedge clk)
+	begin
+		if (wr) begin
+			case(addr)
+			`ADDR_IF : ihold <= iflag | data;
+			`ADDR_IE : imask <= data;
+			endcase
+			
+		end
+		else
+			ihold <= ihold | iflag;
+	end
+
+endmodule
diff --git a/System.v b/System.v
index 8bc14e9..a5fee66 100644
--- a/System.v
+++ b/System.v
@@ -70,9 +70,7 @@ module CoreTop(
 	output wire [3:0] digits,
 	output wire [7:0] seven);
 	
-	wire clk;
-	//IBUFG ibuf (.O(clk), .I(iclk));
-	
+	wire clk;	
 	CPUDCM dcm (.CLKIN_IN(xtal), .CLKFX_OUT(clk));
 
 	wire [15:0] addr;	
@@ -111,7 +109,7 @@ module CoreTop(
 		.switches(switches)
 		);
 
-	UART nouart (
+	UART nouart (	/* no u */
     .clk(clk), 
     .wr(wr), 
     .rd(rd), 
@@ -126,6 +124,30 @@ module CoreTop(
 		.clk(clk),
 		.wr(wr),
 		.rd(rd));
+
+	wire irq, tmrirq;
+	wire [7:0] jaddr;
+	Timer tmr(
+		.clk(clk),
+		.wr(wr),
+		.rd(rd),
+		.addr(addr),
+		.data(data),
+		.irq(tmrirq));
+	
+	Interrupt intr(
+		.clk(clk),
+		.rd(rd),
+		.wr(wr),
+		.addr(addr),
+		.data(data),
+		.vblank(0),
+		.lcdc(0),
+		.tovf(tmrirq),
+		.serial(0),
+		.buttons(0),
+		.master(irq),
+		.jaddr(jaddr));
 endmodule
 
 module TestBench();
@@ -168,6 +190,30 @@ module TestBench();
 		.rd(rd),
 		.serial(serio));
 	
+	wire irq, tmrirq;
+	wire [7:0] jaddr;
+	Timer tmr(
+		.clk(clk),
+		.wr(wr),
+		.rd(rd),
+		.addr(addr),
+		.data(data),
+		.irq(tmrirq));
+	
+	Interrupt intr(
+		.clk(clk),
+		.rd(rd),
+		.wr(wr),
+		.addr(addr),
+		.data(data),
+		.vblank(0),
+		.lcdc(0),
+		.tovf(tmrirq),
+		.serial(0),
+		.buttons(0),
+		.master(irq),
+		.jaddr(jaddr));
+	
 //	Switches sw(
 //		.clk(clk),
 //		.address(addr),
diff --git a/Timer.v b/Timer.v
new file mode 100644
index 0000000..0481614
--- /dev/null
+++ b/Timer.v
@@ -0,0 +1,65 @@
+`define ADDR_DIV  16'hFF04
+`define ADDR_TIMA 16'hFF05
+`define ADDR_TMA  16'hFF06
+`define ADDR_TAC  16'hFF07
+
+module Timer(
+	input clk,
+	input wr,
+	input rd,
+	input [15:0] addr,
+	inout [7:0] data,
+	output reg irq);
+
+	reg [7:0] tima = 0, tma = 0, tac = 0, div = 0;
+	reg ovf = 0;
+	reg [9:0] clkdv;
+
+	wire is_tima = addr == `ADDR_TIMA;
+	wire is_tma  = addr == `ADDR_TMA;
+	wire is_tac  = addr == `ADDR_TAC;
+
+	assign data = rd ?
+	                 is_tima ? tima :
+	                 is_tma ? tma :
+	                 is_tac ? tac :
+	                 8'bzzzzzzzz :
+	              8'bzzzzzzzz;
+
+	wire cksel = tac[2] ?
+	                (tac[1:0] == 2'b00) ? (clkdv == 10'b0)     :
+	                (tac[1:0] == 2'b01) ? (clkdv[3:0] == 4'b0) :
+	                (tac[1:0] == 2'b10) ? (clkdv[5:0] == 6'b0) :
+	                (clkdv[7:0] == 8'b0) :
+	             0;
+
+	always @ (negedge clk) 
+	begin
+		if(wr) begin
+			case(addr)
+			`ADDR_DIV: div <= 8'b0;
+			`ADDR_TIMA: tima <= data;
+			`ADDR_TMA: tma <= data;
+			`ADDR_TAC: tac <= data;
+			endcase
+		end
+		else begin
+			if(ovf) begin
+				tima <= tma;
+				ovf <= 0;
+				irq <= 1;
+			end
+			else begin
+				if(cksel)
+					{ovf,tima} <= {1'b0,tima} + 1;
+				if(irq)
+					irq <= 0;
+			end
+
+			if(clkdv[7:0] == 8'b0)
+				div <= div + 1;
+		end
+		clkdv <= clkdv + 1;
+	end
+
+endmodule
diff --git a/rom.asm b/rom.asm
index 2e98e13..93f8524 100644
--- a/rom.asm
+++ b/rom.asm
@@ -104,13 +104,20 @@ waitsw:
 	ld hl,waitswstr
 	call puts
 	
+	ld c, $07
+	ld a, $07	;start timer, 4.096KHz
+	ld [c], a
+	
 	ld c, $51
 	ld a, $00
 	ld [c],a
 	
+.loop1:
+	push bc
+	call testa
+	pop bc
 	ld c, $51
 	ld b, $0
-.loop1:
 	ld a,[c]
 	cp b
 	jr z,.loop1
@@ -121,7 +128,24 @@ waitsw:
 	ret
 
 waitswstr:
-	db "Diagnostic ROM complete; flip switches to nonzero and then to zero to reset.",$0D,$0A,0
+	db "Diagnostic ROM complete; flip switches to nonzero and then to zero to reset. Expect A.",$0D,$0A,0
+
+testa:
+	ld c, $0F
+	ld a, [c]
+	ld b, $00
+	cp b
+	ret z
+	xor a
+	ld [c], a
+	ld hl, $D000
+	ld c, [hl]
+	inc bc
+	ld [hl], c
+	ld a, c
+	ld c, $50
+	ld [c], a
+	ret
 
 ; Core instruction basic acceptance tests.
 insntest:
@@ -232,14 +256,12 @@ insntest:
 
 ; Serial port manipulation functions.
 putc:
-	push af
 	ld b, 0
 	ld c, $50
 .waitport:
 	ld a,[c]
 	cp b
 	jr nz,.waitport
-	pop af
 	ld [c],a
 	ret