Here's the source code and hex for the checksumming routine
  di
  in a,($06)
  push af
  ld hl,$0000
  ld bc,$0700
  jr go
ComeBack:
  in a,($02)
  bit 5,a
  jr nz,TI84P
  bit 7,a
  jr nz,TI83PSE
  ld bc,$1F18
  jr go
TI83PSE:
  ld b,$7F78
  jr go
TI84P:
  in a,($21)
  bit 0,a
  jr nz,TI84PSE
  ld bc,$3F34
  jr go
TI84PSE:
  ld bc,$7F74
go:
  ld a,b
  out ($06),a
  ld de,$4000
loopi:
  ld a,(de)
  add a,l
  ld l,a
  adc a,h
  sub l
  ld h,a
  inc de
  ld a,d
  cp $80
  jr c,loopi
  dec b
  ld a,c
  cp b
  jr c,go
  ld a,c
  or a
  jr z,ComeBack
  pop af
  out ($06),a
  retF3DB06F52100000100071821DB02CB6F200DCB7F200501181F18120678180EDB21CB47200501343F180301747F78D3061100401A856F8C9567137AFE8038F40579B838E979B728C4F1D306C9I've tested it and it doesn't crash. Note that it should be its own subroutine because it returns when it's done.
On my calc, it took a couple seconds to run (I enclosed it in an Axe program).

Here's the source code and hex for the checksumming routine

Code: [Select]

 di
  in a,($06)
  push af
  ld hl,$0000
  ld bc,$0700
  jr go
ComeBack:
  in a,($02)
  bit 5,a
  jr nz,TI84P
  bit 7,a
  jr nz,TI83PSE
  ld bc,$1F18
  jr go
TI83PSE:
  ld b,$7F78
  jr go
TI84P:
  in a,($21)
  bit 0,a
  jr nz,TI84PSE
  ld bc,$3F34
  jr go
TI84PSE:
  ld bc,$7F74
go:
  ld a,b
  out ($06),a
  ld de,$4000
loopi:
  ld a,(de)
  add a,l
  ld l,a
  adc a,h
  sub l
  ld h,a
  inc de
  ld a,d
  cp $80
  jr c,loopi
  dec b
  ld a,c
  cp b
  jr c,go
  ld a,c
  or a
  jr z,ComeBack
  pop af
  out ($06),a
  ret

Code: [Select]

F3DB06F52100000100071821DB02CB6F200DCB7F200501181F18120678180EDB21CB47200501343F180301747F78D3061100401A856F8C9567137AFE8038F40579B838E979B728C4F1D306C9I've tested it and it doesn't crash. Note that it should be its own subroutine because it returns when it's done.
On my calc, it took a couple seconds to run (I enclosed it in an Axe program).

Ran it. It returns 0. Is that right, or is it not working?  And what var does it return into? How do I access it from Axe?

Excellent. And how would I save the result into an arbitrary appvar?

thanks