Difference between revisions of "84PCE:Syscalls:021D80"

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(Synopsis)
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[[Category:84PCE:Syscalls:By Name|SignExtendHL_broken]]
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[[Category:84PCE:Syscalls:By Name|SignExtendHL]]
[[Category:84PCE:Syscalls:By Address|021D80 - SignExtendHL_broken]]
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[[Category:84PCE:Syscalls:By Address|021D80 - SignExtendHL]]
 
== Synopsis ==
 
== Synopsis ==
'''Hypothesized Official Name:''' SignExtendHL_broken
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'''Hypothesized Official Name:''' SignExtendHL
  
 
'''Syscall Address:''' 021D80h
 
'''Syscall Address:''' 021D80h
  
This is supposed to extend the signed 16-bit HL value to be 24-bit signed.
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This was originally a buggy call, and still is in OS 5.0.0.0089 (and others, perchance?) But after sending in information, TI did an amazing job and fixed this call. It basically performs a sign extension on a 16bit HL to 24bit HL.
 
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However, due to what looks like a copy-paste error by TI, this routine is pretty much useless.
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It looks like they tried to use code from SignExtendBC, and forgot to change a byte.
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Here is what this routine calls, if you can find a particular use for it, go for it.
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<nowiki>SignExtendHL_broken:
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push af
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  xor a
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  ld (0D02AD7h), hl
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  bit 7, b                ; This should be h, not b
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  jr z, +_
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  dec a
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_:
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  ld (0D02AD9h), a
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  ld de, (0D02AD7h)
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pop af
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ret </nowiki>
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Revision as of 11:29, 4 September 2015

Synopsis

Hypothesized Official Name: SignExtendHL

Syscall Address: 021D80h

This was originally a buggy call, and still is in OS 5.0.0.0089 (and others, perchance?) But after sending in information, TI did an amazing job and fixed this call. It basically performs a sign extension on a 16bit HL to 24bit HL.