diff options
Diffstat (limited to 'common')
| -rw-r--r-- | common/double_speed.asm | 31 | ||||
| -rw-r--r-- | common/handshake.asm | 38 | ||||
| -rw-r--r-- | common/init.asm | 2 | ||||
| -rw-r--r-- | common/item.asm | 76 | ||||
| -rw-r--r-- | common/predef.asm | 54 | ||||
| -rw-r--r-- | common/random.asm | 76 | ||||
| -rw-r--r-- | common/sram.asm | 34 |
7 files changed, 310 insertions, 1 deletions
diff --git a/common/double_speed.asm b/common/double_speed.asm new file mode 100644 index 000000000..fc1234215 --- /dev/null +++ b/common/double_speed.asm @@ -0,0 +1,31 @@ +; The CGB hardware introduces Double Speed Mode. +; While active, the clock speed is doubled. + +; The hardware can switch between normal speed +; and double speed at any time, but LCD output +; collapses during the switch. + +DoubleSpeed: ; 2fef + ld hl, rKEY1 + bit 7, [hl] + jr z, SwitchSpeed + ret +; 2ff7 + +NormalSpeed: ; 2ff7 + ld hl, rKEY1 + bit 7, [hl] + ret z +; 2ffd + +SwitchSpeed: ; 2ffd + set 0, [hl] + xor a + ld [rIF], a + ld [rIE], a + ld a, $30 + ld [rJOYP], a + stop ; rgbasm adds a nop after this instruction by default + ret +; 300b + diff --git a/common/handshake.asm b/common/handshake.asm new file mode 100644 index 000000000..8ed1473e4 --- /dev/null +++ b/common/handshake.asm @@ -0,0 +1,38 @@ +AskSerial: ; 2063 +; send out a handshake while serial int is off + ld a, [$c2d4] + bit 0, a + ret z + + ld a, [$c2d5] + and a + ret nz + +; once every 6 frames + ld hl, $ca8a + inc [hl] + ld a, [hl] + cp 6 + ret c + + xor a + ld [hl], a + + ld a, $c + ld [$c2d5], a + +; handshake + ld a, $88 + ld [rSB], a + +; switch to internal clock + ld a, %00000001 + ld [rSC], a + +; start transfer + ld a, %10000001 + ld [rSC], a + + ret +; 208a + diff --git a/common/init.asm b/common/init.asm index 3104c416d..ead75975c 100644 --- a/common/init.asm +++ b/common/init.asm @@ -156,7 +156,7 @@ Init: ; 17d ld a, [hCGB] and a jr z, .asm_22b - call Function2ff7 + call NormalSpeed .asm_22b xor a diff --git a/common/item.asm b/common/item.asm new file mode 100644 index 000000000..0906a19f6 --- /dev/null +++ b/common/item.asm @@ -0,0 +1,76 @@ +DoItemEffect: ; 2f3f + callba _DoItemEffect + ret +; 2f46 + +CheckTossableItem: ; 2f46 + push hl + push de + push bc + callba _CheckTossableItem + pop bc + pop de + pop hl + ret +; 2f53 + +TossItem: ; 2f53 + push hl + push de + push bc + ld a, [hROMBank] + push af + ld a, BANK(_TossItem) + rst Bankswitch + + call _TossItem + + pop bc + ld a, b + rst Bankswitch + pop bc + pop de + pop hl + ret +; 2f66 + +ReceiveItem: ; 2f66 + push bc + ld a, [hROMBank] + push af + ld a, BANK(_ReceiveItem) + rst Bankswitch + push hl + push de + + call _ReceiveItem + + pop de + pop hl + pop bc + ld a, b + rst Bankswitch + pop bc + ret +; 2f79 + +CheckItem: ; 2f79 + push hl + push de + push bc + ld a, [hROMBank] + push af + ld a, BANK(_CheckItem) + rst Bankswitch + + call _CheckItem + + pop bc + ld a, b + rst Bankswitch + pop bc + pop de + pop hl + ret +; 2f8c + diff --git a/common/predef.asm b/common/predef.asm new file mode 100644 index 000000000..bd34a87a1 --- /dev/null +++ b/common/predef.asm @@ -0,0 +1,54 @@ +Predef: ; 2d83 +; Call predefined function a. +; Preserves bc, de, hl and f. + + ld [PredefID], a + ld a, [hROMBank] + push af + + ld a, BANK(GetPredefPointer) + rst Bankswitch + call GetPredefPointer ; stores hl in PredefTemp + +; Switch to the new function's bank + rst Bankswitch + +; Instead of directly calling stuff, +; push it to the stack in reverse. + + ld hl, .Return + push hl + +; Call the Predef function + ld a, [PredefAddress] + ld h, a + ld a, [PredefAddress + 1] + ld l, a + push hl + +; Get hl back + ld a, [PredefTemp] + ld h, a + ld a, [PredefTemp + 1] + ld l, a + ret + +.Return +; Clean up after the Predef call + + ld a, h + ld [PredefTemp], a + ld a, l + ld [PredefTemp+1], a + + pop hl + ld a, h + rst Bankswitch + + ld a, [PredefTemp] + ld h, a + ld a, [PredefTemp + 1] + ld l, a + ret +; 2dba + diff --git a/common/random.asm b/common/random.asm new file mode 100644 index 000000000..0f46da9e4 --- /dev/null +++ b/common/random.asm @@ -0,0 +1,76 @@ +Random: ; 2f8c +; A simple hardware-based random number generator (RNG). + +; Two random numbers are generated by adding and subtracting +; the divider to the respective values every time it's called. + +; The divider is a register that increments at a rate of 16384Hz. +; For comparison, the Game Boy operates at a clock speed of 4.2MHz. + +; Additionally, an equivalent function is executed in VBlank. + +; This leaves a with the value in hRandomSub. + + push bc + + ld a, [rDIV] + ld b, a + ld a, [hRandomAdd] + adc b + ld [hRandomAdd], a + + ld a, [rDIV] + ld b, a + ld a, [hRandomSub] + sbc b + ld [hRandomSub], a + + pop bc + ret +; 2f9f + +BattleRandom: ; 2f9f +; _BattleRandom lives in another bank. + +; It handles all RNG calls in the battle engine, allowing +; link battles to remain in sync using a shared PRNG. + + ld a, [hROMBank] + push af + ld a, BANK(_BattleRandom) + rst Bankswitch + + call _BattleRandom + + ld [$cfb6], a + pop af + rst Bankswitch + ld a, [$cfb6] + ret +; 2fb1 + + +Function2fb1: ; 2fb1 + push bc + ld c, a + xor a + sub c +.asm_2fb5 + sub c + jr nc, .asm_2fb5 + add c + ld b, a + push bc +.asm_2fbb + call Random + ld a, [hRandomAdd] + ld c, a + add b + jr c, .asm_2fbb + ld a, c + pop bc + call SimpleDivide + pop bc + ret +; 2fcb + diff --git a/common/sram.asm b/common/sram.asm new file mode 100644 index 000000000..3c42e7618 --- /dev/null +++ b/common/sram.asm @@ -0,0 +1,34 @@ +GetSRAMBank: ; 2fcb +; load sram bank a +; if invalid bank, sram is disabled + cp NUM_SRAM_BANKS + jr c, OpenSRAM + jr CloseSRAM +; 2fd1 + +OpenSRAM: ; 2fd1 +; switch to sram bank a + push af +; latch clock data + ld a, 1 + ld [MBC3LatchClock], a +; enable sram/clock write + ld a, SRAM_ENABLE + ld [MBC3SRamEnable], a +; select sram bank + pop af + ld [MBC3SRamBank], a + ret +; 2fe1 + +CloseSRAM: ; 2fe1 + push af + ld a, SRAM_DISABLE +; reset clock latch for next time + ld [MBC3LatchClock], a +; disable sram/clock write + ld [MBC3SRamEnable], a + pop af + ret +; 2fec + |