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STAT IRQ bug and fine X scroll improvement

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paulb-nl
2021-01-06 11:54:48 +01:00
parent ca8b55dfb3
commit 0355ecb458
1 changed files with 23 additions and 17 deletions
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40
rtl/video.v
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@@ -152,7 +152,9 @@ wire lcdc_bg_prio = lcdc[0];
assign lcd_on = lcdc_on;
// ff41 STAT
reg [7:0] stat;
reg [7:0] stat_r;
// DMG STAT bug: IRQs are enabled for 1 cycle during a write
wire [7:0] stat = (cpu_sel_reg & cpu_wr & cpu_addr == 8'h41 & ~isGBC) ? 8'hFF : stat_r;
// ff42, ff43 background scroll registers
reg [7:0] scy;
@@ -330,7 +332,7 @@ assign SS_Video1_BACK[42:35] = scx;
assign SS_Video1_BACK[50:43] = wy;
assign SS_Video1_BACK[58:51] = wx;
assign SS_Video2_BACK[ 7: 0] = stat;
assign SS_Video2_BACK[ 7: 0] = stat_r;
assign SS_Video2_BACK[15: 8] = bgp;
assign SS_Video2_BACK[23:16] = obp0;
assign SS_Video2_BACK[31:24] = obp1;
@@ -373,7 +375,7 @@ always @(posedge clk) begin
scx <= SS_Video1[42:35]; // 8'h00;
wy <= SS_Video1[50:43]; // 8'h00;
wx <= SS_Video1[58:51]; // 8'h00;
stat <= SS_Video2[ 7: 0]; // 8'h00;
stat_r <= SS_Video2[ 7: 0]; // 8'h00;
bgp <= SS_Video2[15: 8]; // 8'hfc;
obp0 <= SS_Video2[23:16]; // 8'hff;
obp1 <= SS_Video2[31:24]; // 8'hff;
@@ -406,7 +408,7 @@ always @(posedge clk) begin
if(cpu_sel_reg && cpu_wr) begin
case(cpu_addr)
8'h40: lcdc <= cpu_di;
8'h41: stat <= cpu_di;
8'h41: stat_r <= cpu_di;
8'h42: scy <= cpu_di;
8'h43: scx <= cpu_di;
// a write to 4 is supposed to reset the v_cnt
@@ -472,7 +474,7 @@ assign cpu_do =
// --------------------------------------------------------------------
reg skip_en;
reg [7:0] skip;
reg [2:0] skip_cnt;
reg [7:0] pcnt;
wire sprite_fetch_hold;
wire bg_shift_empty;
@@ -481,31 +483,35 @@ assign pcnt_end = ( pcnt == (isGBC ? 8'd168 : 8'd167) );
assign pcnt_reset = (h_cnt[1:0] == 2'b11) & end_of_line & ~vblank;
assign SS_Video3_BACK[ 6] = skip_en;
assign SS_Video3_BACK[14: 7] = skip;
assign SS_Video3_BACK[22:15] = pcnt;
assign SS_Video3_BACK[ 9: 7] = skip_cnt;
assign SS_Video3_BACK[17:10] = pcnt;
assign SS_Video3_BACK[22:18] = 5'd0;
always @(posedge clk) begin
if (reset) begin
skip_en <= SS_Video3[ 6]; // 1'b0;
pcnt <= SS_Video3[14: 7]; // 8'd0;
skip <= SS_Video3[22:15]; // 8'd0;
skip_en <= SS_Video3[ 6]; // 1'b0;
skip_cnt <= SS_Video3[ 9: 7]; // 3'd0;
pcnt <= SS_Video3[17:10]; // 8'd0;
end else if (!lcd_on) begin
skip_en <= 1'b0;
pcnt <= 8'd0;
skip <= 8'd0;
skip_en <= 1'b0;
skip_cnt <= 3'd0;
pcnt <= 8'd0;
end else if (ce) begin
// Only skip when not paused for sprites and fifo is not empty.
// This makes it skip pixels when pcnt = 1 after the first tile fetch.
// If window_x = 0 then window starts at pcnt = 1 when it is skipping pixels which scrolls the window.
if (~sprite_fetch_hold & ~bg_shift_empty) begin
if ((pcnt == 0) && |scx[2:0]) begin
skip <= scx[2:0];
skip_cnt <= 3'd1;
skip_en <= 1'b1;
end
if(skip) skip <= skip - 1'd1;
if(skip == 1) skip_en <= 1'b0;
if (skip_en) begin
if(skip_cnt == scx[2:0] || &skip_cnt)
skip_en <= 1'b0;
else
skip_cnt <= skip_cnt + 1'd1;
end
// Pixels 0-7 are for fetching partially offscreen sprites and window.
// Pixels 8-167 are output to the display.