84PCE:Syscalls:021D7C - Revision history

MateoConLechuga: /* Synopsis */

2015-09-04T20:04:56Z

‎Synopsis

MateoConLechuga at 20:04, 4 September 2015

2015-09-04T20:04:45Z

MateoConLechuga: /* Synopsis */

2015-09-04T19:58:02Z

‎Synopsis

MateoConLechuga at 19:57, 4 September 2015

2015-09-04T19:57:53Z

MateoConLechuga at 19:57, 4 September 2015

2015-09-04T19:57:35Z

MateoConLechuga: /* Synopsis */

2015-09-01T21:02:02Z

‎Synopsis

MateoConLechuga: /* Synopsis */

2015-05-05T01:41:05Z

‎Synopsis

MateoConLechuga at 01:40, 5 May 2015

2015-05-05T01:40:19Z

MateoConLechuga at 01:39, 5 May 2015

2015-05-05T01:39:55Z

MateoConLechuga: Created page with "SignExtendDE_broken 021D7C - SignExtendDE_broken == Synopsis == '''Hypothesized Official Name:''' Si..."

2015-05-05T01:39:21Z

Created page with "SignExtendDE_broken 021D7C - SignExtendDE_broken == Synopsis == '''Hypothesized Official Name:''' Si..."

New page

[[Category:84PCE:Syscalls:By Name|SignExtendDE_broken]]
[[Category:84PCE:Syscalls:By Address|021D7C - SignExtendDE_broken]]
== 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.

<nowiki> 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</nowiki>

@@ Line 6: / Line 6: @@
 '''Syscall Address:''' 021D7Ch
-This was originally a broken 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 is known to work in OS 5.1.0.0110.
+This was originally a broken 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.
 === Inputs ===

@@ Line 6: / Line 6: @@
 '''Syscall Address:''' 021D7Ch
-This was originally a broken 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. It is known to work in OS 5.1.0.0110.
+This was originally a broken 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 is known to work in OS 5.1.0.0110.
 === Inputs ===

@@ Line 9: / Line 9: @@
 === Inputs ===
-HL - 16-bit signed value
+DE - 16-bit signed value
 === Outputs ===
-HL - 24-bit signed value
+DE - 24-bit signed value
 === Destroys ===
-* HLU
+* DEU

@@ Line 2: / Line 2: @@
 [[Category:84PCE:Syscalls:By Address|021D7C - SignExtendDE]]
 == Synopsis ==
-'''Hypothesized Official Name:''' SignExtendDE_broken
+'''Hypothesized Official Name:''' SignExtendDE
 '''Syscall Address:''' 021D7Ch

@@ Line 1: / Line 1: @@
-[[Category:84PCE:Syscalls:By Name|SignExtendDE_broken]]
+[[Category:84PCE:Syscalls:By Name|SignExtendDE]]
-[[Category:84PCE:Syscalls:By Address|021D7C - SignExtendDE_broken]]
+[[Category:84PCE:Syscalls:By Address|021D7C - SignExtendDE]]
 == Synopsis ==
 '''Hypothesized Official Name:''' SignExtendDE_broken
@@ Line 6: / Line 6: @@
 '''Syscall Address:''' 021D7Ch
-This is supposed to extend the signed 16-bit DE value to be 24-bit signed.
+This was originally a broken 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. It is known to work in OS 5.1.0.0110.
-However, due to what looks like a copy-paste error by TI, this routine is pretty much useless.
+=== Inputs ===
-It looks like they tried to use code from SignExtendBC, and forgot to change a byte.
+=== Outputs ===
-Here is what this routine calls, if you can find a particular use for it, go for it.
+=== Destroys ===
+* HLU
- <nowiki>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 </nowiki>

@@ Line 14: / Line 14: @@
 Here is what this routine calls, if you can find a particular use for it, go for it.
-<nowiki> push af
+ <nowiki> push af
   xor a
   ld (0D02AD7h), de
@@ Line 24: / Line 24: @@
   ld de, (0D02AD7h)
   pop af
-  ret</nowiki>
+  ret </nowiki>