Difference between revisions of "84PCE:Syscalls:021D7C"

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Line 16: Line 16:
 
  <nowiki>SignExtendDE_broken:
 
  <nowiki>SignExtendDE_broken:
 
  push af
 
  push af
−
xor a
+
  xor a
−
ld (0D02AD7h), de
+
  ld (0D02AD7h), de
−
bit 7, b                ; This should be d, not b
+
  bit 7, b                ; This should be d, not b
−
jr z, _+
+
  jr z, _+
−
dec a
+
  dec a
 
_+:
 
_+:
−
ld (0D02AD9h), a
+
  ld (0D02AD9h), a
−
ld de, (0D02AD7h)
+
  ld de, (0D02AD7h)
 
  pop af
 
  pop af
 
  ret </nowiki>
 
  ret </nowiki>

Revision as of 17:41, 4 May 2015

Synopsis

Hypothesized Official Name: SignExtendDE_broken

Syscall Address: 021D7Ch

This is supposed to extend the signed 16-bit DE 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. 

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