Skip to content
New issue

Have a question about this project? Sign up for a free GitHub account to open an issue and contact its maintainers and the community.

Sign up for GitHub

By clicking “Sign up for GitHub”, you agree to our terms of service and privacy statement. We’ll occasionally send you account related emails.

Already on GitHub? Sign in to your account

Jump to bottom

Fix Chip8 HiRes mode #37

Merged
merged 1 commit into from Oct 4, 2020
Merged

Fix Chip8 HiRes mode #37

Changes from all commits
Commits
Show all changes
1 commit
Select commit
File filter

Filter by extension

Filter by extension
Conversations
Failed to load comments.
Jump to
Jump to file
Failed to load files.
Diff view
Diff view
19 changes: 17 additions & 2 deletions src/chip8/chip8.cpp
View file
Open in desktop
Expand Up @@ -160,11 +160,26 @@ inline void Chip8::setSuperhires(bool enabled) {
inline void Chip8::groupJump(uint16_t inst) {
// Hack for handling original 64x64 Hi-Res mode
// HiRes ML routines were at 200-248, hi-res
// programs started at 0x260.
// programs started at 0x2c0. They always start
// with a jump to 0x0260, which runs a setup routine
// in chip8/native asm:
// * 6012 61be a200 f155
// Rewrite the first chip8 instruction to be a jump to 0x12be
// * A series of reads of 0x200 space followed by writes to 0x000
// space, presumably copying some native 1802 code contained in
// the Chip8 rom into the emulator space.
// * It ends with 0x02ac at program address 0x02ac,
// which jumps to a native RCA1802 routine at that location.
// That routine eventually returns to running the chip8
// program. So in the emulator.
if(mState.PC == 0x200 && inst == 0x1260) {
// Do what the ML code would do.
mRender.setMode(CHIP8HI);
// Re-enter 0x0200, which is just going to jump to 0x02be.
mState.NextPC = 0x02c0;
} else {
mState.NextPC = imm12(inst);
}
mState.NextPC = imm12(inst);
}

// 02nnn call
Expand Down