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improved version of mbc1/2 special case handling

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This commit is contained in:
Robert Peip
2021-01-28 18:13:53 +01:00
parent f702d5486b
commit 73cbb3a1cd
2 changed files with 4 additions and 16 deletions
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10
Gameboy.sv
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@@ -445,21 +445,15 @@ always @(posedge clk_sys) begin
//write to ROM bank register
if(cart_wr && (cart_addr[15:13] == 3'b001)) begin
if(~mbc5 && cart_di[6:0]==0) //special case mbc1-3 rombank 0=1
if(~mbc5 && (cart_di[6:0]==0 || (mbc1 && cart_di[4:0]==0) || (mbc2 && cart_di[3:0]==0))) //special case mbc1-3 rombank 0=1
mbc_rom_bank_reg <= 5'd1;
else if (mbc5) begin
if (cart_addr[13:12] == 2'b11) //3000-3FFF High bit
mbc_rom_bank_reg[8] <= cart_di[0];
else //2000-2FFF low 8 bits
mbc_rom_bank_reg[7:0] <= cart_di[7:0];
end else begin
end else
mbc_rom_bank_reg <= {2'b00,cart_di[6:0]}; //mbc1-3
if (mbc1 || mbc2) begin
if (cart_di[6:0] == 7'h20) mbc_rom_bank_reg <= 9'h021;
if (cart_di[6:0] == 7'h40) mbc_rom_bank_reg <= 9'h041;
if (cart_di[6:0] == 7'h60) mbc_rom_bank_reg <= 9'h061;
end
end
end
//write to RAM bank register

10
sim/src/gameboy/mbc.sv
View File

@@ -174,21 +174,15 @@ always @(posedge clk_sys) begin
//write to ROM bank register
if(cart_wr && (cart_addr[15:13] == 3'b001)) begin
if(~mbc5 && cart_di[6:0]==0) //special case mbc1-3 rombank 0=1
if(~mbc5 && (cart_di[6:0]==0 || (mbc1 && cart_di[4:0]==0) || (mbc2 && cart_di[3:0]==0))) //special case mbc1-3 rombank 0=1
mbc_rom_bank_reg <= 5'd1;
else if (mbc5) begin
if (cart_addr[13:12] == 2'b11) //3000-3FFF High bit
mbc_rom_bank_reg[8] <= cart_di[0];
else //2000-2FFF low 8 bits
mbc_rom_bank_reg[7:0] <= cart_di[7:0];
end else begin
end else
mbc_rom_bank_reg <= {2'b00,cart_di[6:0]}; //mbc1-3
if (mbc1 || mbc2) begin
if (cart_di[6:0] == 7'h20) mbc_rom_bank_reg <= 9'h021;
if (cart_di[6:0] == 7'h40) mbc_rom_bank_reg <= 9'h041;
if (cart_di[6:0] == 7'h60) mbc_rom_bank_reg <= 9'h061;
end
end
end
//write to RAM bank register