84PCE:Syscalls:021D80

Synopsis

Hypothesized Official Name: SignExtendHL_broken

Syscall Address: 021D80h

This is supposed to extend the signed 16-bit HL value to be 24-bit signed.

However, due to what looks like a copy-paste error by TI, this routine is pretty much useless.

It looks like they tried to use code from SignExtendBC, and forgot to change a byte.

Here is what this routine calls, if you can find a particular use for it, go for it.

SignExtendHL_broken:
 push af
  xor a
  ld (0D02AD7h), hl
  bit 7, b                ; This should be h, not b
  jr z, +_
  dec a
_:
  ld (0D02AD9h), a
  ld de, (0D02AD7h)
 pop af
 ret