interupt_loader.c

#pragma once
 
 
// Location of line 45 at:
// https://github.com/z88dk/z88dk/blob/master/lib/target/ti83p/classic/intwrap83p.asm
//
 
#define interrupt_rst38 24 + 0x8A8A
 
#define basepage 0x8AFF
// Only have 69 bytes to work with
#define loader_point 48 + 0x8A8A
 
#define interrupt_mask  0b00001011
#define interrupt_acknowledge 0b00001000
 
 
// Effectivly "ret" but to +3 of normal value, and acknowledges that interupt ran
#define CI_RET pop de \ ld hl, 7 \ add hl, de \\
         ld a, interrupt_mask \ out (3), a \
         \ jp (hl) 
 
 
// Restore old opcodes to the interupt ram
void unpatch_ram() __naked{
    #asm
    di
#ifdef FLASH_APP
    ld hl, interrupt_rst38-2
#else
    ld hl, 0x8A8A+1
    ld e, (hl)
    inc hl
    ld d, (hl)
    ld hl, 24-2 // Calculate where location based on the jp instruction 
    add hl, de  // created by the interupt loader   
#endif
    ld (hl), $D9 // Exx
    inc hl
    ld (hl), $08 // ex af, af
    inc hl
    ld (hl), $FF // rst 38h
    inc hl
    ld (hl), $F3 // di
    inc hl
    ld (hl), $F3 // di
    inc hl
    ld (hl), $08 // ex af, af
    inc hl
    ld (hl), $D9 // Exx
    
 
    ret
 
 
    #endasm
}
 
void patch_ram() __naked{
    #asm
    di
 
#ifdef FLASH_APP
    in a,(6)
    ld (basepage), a
 
    ld hl, interrupt_rst38-2
    
#else
    ld hl, 0x8A8A+1
    ld e, (hl)
    inc hl
    ld d, (hl)
    ld hl, 24-2 // Calculate where location based on the jp instruction 
    add hl, de  // created by the interupt loader
    
#endif
    ld a, 0xF3
    ld (hl), a // Replace "exx" with "di"
    inc hl
    xor a, a
    ld (hl), a // Replace "ex af,af" with "nop"
    inc hl
 
 
 
    // replace calling the default system interupts with calling the interupt loader
    ld (hl), 0xCd // "Call" opcode
    inc hl
    #ifdef FLASH_APP
    ld (hl), (loader_point) &0xFF
    inc hl
    ld (hl), (loader_point) >> 8
    #else
    ld (hl), (USER_INTERUPT_LOADER) &0xFF
    inc hl
    ld (hl), (USER_INTERUPT_LOADER) >> 8
    #endif
    xor a, a
    inc hl
    ld (hl), a // Replace "ex af,af" with "nop"
    inc hl
    ld (hl), a // Replace "exx" with "nop"
 
    #ifdef FLASH_APP
    ld hl, USER_INTERUPT_LOADER
    ld de, loader_point
    ld bc, END_OF_USER_INTERUPT_LOADER-USER_INTERUPT_LOADER
 
    ldir
    #endif
    ei
    ret
    #endasm
 
 
 
 
    #asm
USER_INTERUPT_LOADER:
#ifdef FLASH_APP
 
    in a,(6)
    push af
    ld a,(basepage)
    out (6),a
#endif
    call USER_INTERUPT
 
    exx
    ex af, af
 
    rst $38         ;
    di              ; 'BIG' HOLE HERE... (TIOS does ei...)
    di
    exx
    ex af, af
 
    // Effectivly rets here on CI_RET by adding to the return value
 
#ifdef FLASH_APP
    pop af
    out (6),a
#endif
    ret
END_OF_USER_INTERUPT_LOADER:
    #endasm
 
 
 
 
}