hello.z80

#include "ti83plus.inc"
.org userMem-2
.db $BB,$6D


    bcall(_RclAns)
    bcall(_ConvOp1)
    ld a,e
    or a
    jr z,Install_Interrupt
    dec a
    ret nz
Uninstall_Interrupt:
    im 1
    ret
Install_Interrupt:

    di
    ld hl,$9900
    ld de,$9901
    ld bc,256
    ld (hl),$9a
    ldir


    ld  hl,interrupt_start
    ld  de,$9a9a
    ld  bc,interrupt_end-interrupt_start
    ldir
    ld  a,$99
    ld  i,a
    im  2           ;switch to mode 2
    ei              ;enable interrupts
    ret




Interrupt_Start:
    ex af,af'
    exx
    in a,($03)
    and %11111110
    out ($03),a
    call $003A
    reti
Interrupt_End:
.end