Apple-1-HW
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verilog-apple-one
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VGA module works. Still no hardware scrolling though

This commit is contained in:
Alan Garfield 2018-02-06 00:29:56 +11:00
parent 7b3c65b8d9
commit 25aff9cdc3
5 changed files with 123 additions and 96 deletions
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80
roms/vga_vram.bin
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8
rtl/apple1.v
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@ -58,12 +58,10 @@ module apple1(
// Clocks
wire cpu_clken;
wire blink_clken;
clock my_clock(
.clk25(clk25),
.rst_n(rst_n),
.cpu_clken(cpu_clken),
.blink_clken(blink_clken)
.cpu_clken(cpu_clken)
);
//////////////////////////////////////////////////////////////////////////
@ -196,9 +194,7 @@ module apple1(
.address(ab[0]),
.w_en(we & vga_cs),
.din(dbo),
.blink_clken(blink_clken)
.din(dbo)
);
//////////////////////////////////////////////////////////////////////////

19
rtl/clock.v
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@ -28,8 +28,7 @@ module clock(
input rst_n, // active low synchronous reset
// Clock enables
output reg cpu_clken, // 1MHz clock enable for the CPU and devices
output reg blink_clken // 1Hz clock enable for cursor blink
output reg cpu_clken // 1MHz clock enable for the CPU and devices
);
// generate clock enable once every
@ -70,20 +69,4 @@ module clock(
end
`endif
reg [20:0] bclk_div;
always @(posedge clk25)
begin
// note: bclk_div should be compared to
// N-1, where N is the clock divisor
if (cpu_clken)
begin
if ((bclk_div == 500000) || (rst_n == 1'b0))
bclk_div <= 0;
else
bclk_div <= bclk_div + 1'b1;
blink_clken <= (bclk_div[20:0] == 0);
end
end
endmodule

2
rtl/vga/font_rom.v
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@ -48,7 +48,7 @@ module font_rom(
wire [3:0] line_ptr = line[4:1];
always @(posedge clk)
out <= rom[(character * 10) + {2'd0, line_ptr}][pixel_ptr];
out <= (line[0] & pixel[0]) ? rom[(character * 10) + {2'd0, line_ptr}][pixel_ptr] : 1'b0;
endmodule

110
rtl/vga/vga.v
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@ -9,12 +9,11 @@ module vga(
output vga_blu, // blue VGA signal
input address, // address bus
input w_en, // active high write enable strobe
input [7:0] din, // 8-bit data bas (input)
input blink_clken // cursor blink enable strobe
input [7:0] din // 8-bit data bas (input)
);
//////////////////////////////////////////////////////////////////////////
// VGA Sync Generation
// Registers and Parameters
// video structure constants
parameter h_pixels = 799; // horizontal pixels per line
@ -32,17 +31,41 @@ module vga(
wire [3:0] h_dot;
reg [4:0] v_dot;
// hardware cursor registers
wire [9:0] cursor;
reg [5:0] h_cursor;
reg [4:0] v_cursor;
reg [9:0] v_cursor;
// vram indexing registers
reg [9:0] vram_start_addr;
reg [5:0] vram_h_addr;
reg [9:0] vram_v_addr;
// vram registers
wire [9:0] vram_r_addr;
reg [9:0] vram_w_addr;
reg vram_w_en;
reg [5:0] vram_din;
wire [5:0] vram_dout;
// font rom registers
wire [5:0] font_char;
wire [3:0] font_pixel;
wire [4:0] font_line;
wire font_out;
// cpu control registers
reg char_seen;
// active region strobes
wire h_active;
wire v_active;
assign h_active = (h_cnt >= hbp && h_cnt < hfp);
assign v_active = (v_cnt >= vbp && v_cnt < vfp);
assign vga_h_sync = (h_cnt < h_pulse) ? 0 : 1;
assign vga_v_sync = (v_cnt < v_pulse) ? 0 : 1;
//////////////////////////////////////////////////////////////////////////
// VGA Sync Generation
//
always @(posedge clk25 or posedge rst)
begin
if (rst)
@ -90,11 +113,6 @@ module vga(
//////////////////////////////////////////////////////////////////////////
// Character ROM
wire [5:0] font_char;
wire [3:0] font_pixel;
wire [4:0] font_line;
wire font_out;
font_rom my_font_rom(
.clk(clk25),
.character(font_char),
@ -106,12 +124,6 @@ module vga(
//////////////////////////////////////////////////////////////////////////
// Video RAM
wire [9:0] vram_r_addr;
reg [9:0] vram_w_addr;
reg vram_w_en;
reg [5:0] vram_din;
wire [5:0] vram_dout;
vram my_vram(
.clk(clk25),
.read_addr(vram_r_addr),
@ -122,10 +134,6 @@ module vga(
.dout(vram_dout)
);
reg [5:0] vram_h_addr;
reg [9:0] vram_v_addr;
//////////////////////////////////////////////////////////////////////////
// Video Signal Generation
@ -151,25 +159,53 @@ module vga(
end
end
assign vram_r_addr = ({4'd0, vram_h_addr} + vram_v_addr);
assign font_char = vram_dout;
//////////////////////////////////////////////////////////////////////////
// Cursor blink
reg blink;
reg [22:0] blink_div;
always @(posedge clk25 or posedge rst)
begin
if (rst)
blink_div <= 0;
else
begin
blink_div <= blink_div + 1;
if (blink_div == 23'd0)
blink <= ~blink;
end
end
//////////////////////////////////////////////////////////////////////////
// Pipeline and VGA signals
// vram to font rom to display pipeline assignments
assign cursor = ({4'd0, h_cursor} + v_cursor);
assign vram_r_addr = (vram_start_addr + {4'd0, vram_h_addr} + vram_v_addr);
assign font_char = (vram_r_addr != cursor) ? vram_dout : (blink) ? 6'd0 : 6'd32;
assign font_pixel = h_dot + 1; // offset by one to get pixel into right cycle,
// font output one pixel clk behind
assign font_line = v_dot;
// vga signals out to monitor
assign vga_red = font_out;
assign vga_grn = font_out;
assign vga_blu = font_out;
assign vga_h_sync = (h_cnt < h_pulse) ? 0 : 1;
assign vga_v_sync = (v_cnt < v_pulse) ? 0 : 1;
reg char_seen;
//////////////////////////////////////////////////////////////////////////
// CPU control and hardware cursor
always @(posedge clk25 or posedge rst)
begin
if (rst)
begin
h_cursor <= 6'd0;
v_cursor <= 5'd0;
v_cursor <= 10'd0;
char_seen <= 0;
vram_start_addr <= 0;
end
else
begin
@ -187,16 +223,16 @@ module vga(
begin
// handle carriage return
h_cursor <= 0;
v_cursor <= v_cursor + 1;
v_cursor <= v_cursor + 10'h28;
end
8'h7F:
// ignore the DDR call to the PIA
h_cursor <= h_cursor + 1;
h_cursor <= 0;
default:
begin
vram_w_addr <= ((v_cursor * 40) + {4'b0, h_cursor});
vram_w_addr <= cursor;
vram_din <= {~din[6], din[4:0]};
vram_w_en <= 1;
@ -210,13 +246,25 @@ module vga(
v_cursor <= v_cursor + 1;
end
if (v_cursor == 920)
begin
// force cursor to start at bottom of screen
// FIXME: now we need to scroll
v_cursor <= 920;
vram_start_addr <= vram_start_addr + 10'h28;
end
if (vram_start_addr >= 920)
vram_start_addr <= 0;
/*
if (v_cursor == 23)
begin
// here we need to add the scroll, probably by moving the
// HEAD of vram up one line
v_cursor <= 0;
vram_start_addr <= vram_start_addr + 10'h28;
end
*/
end
else if(~enable & ~w_en)
char_seen <= 0;