.binarymode TI8X

CurAble = 2
CurOn = 3
CurLock = 4
CurFlags = 12

appBackupScreen = $9872
TSRcode = appBackupScreen
TSRvectors = $9900

.org $9D93
.db $bb,$6d
start:
    ld de,TSRcode
    ld hl,ISR
    ld bc,ISR_end - ISR
    ldir

    ld hl,TSRcode
    ld (TSRvectors), hl
    ld hl,TSRvectors
    ld de,TSRvectors + 2
    ld bc, 254
    ldir

    ld a, TSRvectors >> 8
    ld i, a
    im 2
    ret

ISR:
    set CurLock, (IY+CurFlags)
    jp $0038
ISR_end: