rtl/gfx: implement double-buffered scanout

1 files changed, 31 insertions, 0 deletions

diff --git a/rtl/gfx/gfx_mask_sram.sv b/rtl/gfx/gfx_mask_sram.sv
new file mode 100644
index 0000000..730ee12
--- /dev/null
+++ b/rtl/gfx/gfx_mask_sram.sv
@@ -0,0 +1,31 @@
+`include "gfx/gfx_defs.sv"
+
+module gfx_mask_sram
+(
+	input  logic        clk,
+
+	input  logic        set,
+	                    write,
+	input  linear_coord write_addr,
+	                    read_addr,
+	output logic        mask
+);
+
+	logic mem[`GFX_LINEAR_RES];
+	logic mask_hold, write_hold, set_hold;
+	linear_coord read_addr_hold, write_addr_hold;
+
+	always_ff @(posedge clk) begin
+		mask <= mask_hold;
+		mask_hold <= mem[read_addr_hold];
+		read_addr_hold <= read_addr;
+
+		set_hold <= set;
+		write_hold <= write;
+		write_addr_hold <= write_addr;
+
+		if (write_hold)
+			mem[write_addr_hold] <= set_hold;
+	end
+
+endmodule