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OpenSNES
Modern Open-Source SNES Development SDK
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OpenSNES
Modern Open-Source SNES Development SDK
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Volatile types for hardware register access. More...
Macros | |
| #define | FAR /* host compilers (the clang syntax lint) have no address spaces */ |
| Place a global in bank $7E WRAM, outside the 8 KB bank-0 band. | |
| #define | RAM_CODE /* host compilers (the clang syntax lint) */ |
| Run a function from WRAM instead of ROM. | |
Typedefs | |
| typedef volatile s16 | vs16 |
| typedef volatile s32 | vs32 |
| typedef volatile s8 | vs8 |
| typedef volatile u16 | vu16 |
| typedef volatile u32 | vu32 |
| typedef volatile u8 | vu8 |
Volatile types for hardware register access.
Use these when accessing memory-mapped I/O registers to prevent the compiler from optimizing away reads/writes.
| #define FAR /* host compilers (the clang syntax lint) have no address spaces */ |
Place a global in bank $7E WRAM, outside the 8 KB bank-0 band.
FAR u8 buffer[4096]; — the object lives in $7E:2000-$FFFF and every access to it (direct, buffer[i], or through a u8 FAR * pointer) is compiled with bank-honouring addressing. Use it for bulk state that does not fit the 8 KB band: HDMA tables, tilemaps built in RAM, entity pools. Restrictions: static storage only (the stack is bank 0) and not const (ROM is already reachable from any bank). Initialisers work (the boot data-init copy carries the bank); everything else is zero at boot. Handing a FAR pointer to code expecting a plain pointer is a compile error, as with const; a plain pointer converts to FAR silently and just takes the far path. A T FAR * converts to const T * without a cast — a read through a const pointee is already a far read — so the DMA/HDMA/asset helpers take FAR buffers as they are. Cost: arr[i] on a FAR array is one absolute-long-indexed instruction (cheaper than bank 0); a pointer walk is within 4 % of the bank-0 path.
| #define RAM_CODE /* host compilers (the clang syntax lint) */ |
Run a function from WRAM instead of ROM.
RAM_CODE void wait_for_job(void) { ... } — the function is linked in the RAM code window (RAM_CODE_SIZE in the Makefile, at the top of bank $7E), stored in ROM and copied there by crt0 at boot; callers reach it with an ordinary call. It is for code that must run while the CPU cannot read the ROM (a Super FX job with RON = 1): then it must not call a ROM function (library, runtime helpers such as multiplication, other non-RAM_CODE functions) nor read const data, which lives in ROM. A project with no window fails to assemble with a message naming the function.
1.16.1