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| author | Daniel Harding <33dannye@gmail.com> | 2021-09-19 00:21:14 -0500 |
|---|---|---|
| committer | GitHub <noreply@github.com> | 2021-09-19 00:21:14 -0500 |
| commit | df67aac83b466dadf5f74c881bf84dd9ef19bdfc (patch) | |
| tree | 47501aced2d256052b8f78bc97328d5af5703add /src/home/time.asm | |
| parent | e4bce9b7ee5e89f8edfd921de2379f0fa06af206 (diff) | |
| parent | 8dee6b7a11e85d6d4b9f8ec9fb9d53a499fd37dc (diff) | |
Merge pull request #110 from ElectroDeoxys/master
Split Home bank
Diffstat (limited to 'src/home/time.asm')
| -rw-r--r-- | src/home/time.asm | 93 |
1 files changed, 93 insertions, 0 deletions
diff --git a/src/home/time.asm b/src/home/time.asm new file mode 100644 index 0000000..8b8cda2 --- /dev/null +++ b/src/home/time.asm @@ -0,0 +1,93 @@ +; timer interrupt handler +TimerHandler: + push af + push hl + push de + push bc + ei + call SerialTimerHandler + ; only trigger every fourth interrupt ≈ 60.24 Hz + ld hl, wTimerCounter + ld a, [hl] + inc [hl] + and $3 + jr nz, .done + ; increment the 60-60-60-255-255 counter + call IncrementPlayTimeCounter + ; check in-timer flag + ld hl, wReentrancyFlag + bit IN_TIMER, [hl] + jr nz, .done + set IN_TIMER, [hl] + ldh a, [hBankROM] + push af + ld a, BANK(SoundTimerHandler) + call BankswitchROM + call SoundTimerHandler + pop af + call BankswitchROM + ; clear in-timer flag + ld hl, wReentrancyFlag + res IN_TIMER, [hl] +.done + pop bc + pop de + pop hl + pop af + reti + +; increment play time counter by a tick +IncrementPlayTimeCounter: + ld a, [wPlayTimeCounterEnable] + or a + ret z + ld hl, wPlayTimeCounter + inc [hl] + ld a, [hl] + cp 60 + ret c + ld [hl], $0 + inc hl + inc [hl] + ld a, [hl] + cp 60 + ret c + ld [hl], $0 + inc hl + inc [hl] + ld a, [hl] + cp 60 + ret c + ld [hl], $0 + inc hl + inc [hl] + ret nz + inc hl + inc [hl] + ret + +; setup timer to 16384/68 ≈ 240.94 Hz +SetupTimer: + ld b, -68 ; Value for Normal Speed + call CheckForCGB + jr c, .set_timer + ldh a, [rKEY1] + and $80 + jr z, .set_timer + ld b, $100 - 2 * 68 ; Value for CGB Double Speed +.set_timer + ld a, b + ldh [rTMA], a + ld a, TAC_16384_HZ + ldh [rTAC], a + ld a, TAC_START | TAC_16384_HZ + ldh [rTAC], a + ret + +; return carry if not CGB +CheckForCGB: + ld a, [wConsole] + cp CONSOLE_CGB + ret z + scf + ret |