STY: Difference between revisions

Latest revision as of 06:41, 22 August 2024


Basic Info
Addressing Mode	Opcode	Length	Speed
Absolute	8C	3 bytes	4 cycles*
Direct Page	84	2 bytes	3 cycles*
Direct Page Indexed by X	94	2 bytes	4 cycles*


Flags Affected
N	V	M	X	D	I	Z	C
.	.	.	.	.	.	.	.

STY (Store Y) is a 65x instruction that stores the value of the Y index register. If Y is 16-bit, its high byte is stored to the effective address plus one.

No flags are affected.

Syntax

STY addr
STY dp
STY dp, X

Cycle Penalties

STY takes one additional cycle when the index registers are 16 bits wide, in all addressing modes.
In both direct page addressing modes only, STY takes another additional cycle if the low byte of the direct page register is nonzero.

External Links

Eyes & Lichty, page 506 on STY
Labiak, page 187 on STY
7.3 on MCS6500 Manual, page 97 on STY
Carr, page 274 on STY
Leventhal, page 3-98 on STY
snes9x implementation of STY: https://github.com/snes9xgit/snes9x/blob/master/cpuops.cpp#L1302
undisbeliever on STY: https://undisbeliever.net/snesdev/65816-opcodes.html#sty-store-index-register-y-to-memory
Pickens, John. http://www.6502.org/tutorials/6502opcodes.html#STY

@@ Line 1: / Line 1: @@
-'''STY''' (Store Y) is a 65x instruction that stores the value of the [[Y index register]].
 {| class="wikitable" style="float:right;clear:right;width:40%"
 !colspan="8"|Basic Info
@@ Line 9: / Line 7: @@
 |'''Speed'''
 |+
-|absolute
+|[[Absolute]]
 |8C
 |3 bytes
-|4 cycles
+|4 cycles*
 |+
-|direct page
+|[[Direct Page Addressing|Direct Page]]
 |84
 |2 bytes
-|3 cycles
+|3 cycles*
 |+
-|direct page indexed Y
+|[[Direct Page Indexed by X]]
-|96
+|94
 |2 bytes
-|4 cycles
+|4 cycles*
 |}
 {| class="wikitable" style="float:right;clear:right;width:30%"
-!colspan="9"|Flags Clobbered
+!colspan="9"|Flags Affected
 |+
-|N
+|[[Negative Flag|N]]
-|V
+|[[Overflow Flag|V]]
-|M
+|[[M Flag|M]]
-|X
+|[[X Flag|X]]
-|D
+|[[Decimal Flag|D]]
-|I
+|[[I Flag|I]]
-|Z
+|[[Zero Flag|Z]]
-|C
+|[[Carry Flag|C]]
 |+
 |.
@@ Line 46: / Line 44: @@
 |.
 |}
+'''STY''' (Store Y) is a 65x instruction that stores the value of the [[Y index register]].  If Y is 16-bit, its high byte is stored to the effective address plus one.
+No flags are affected.
+==== Syntax ====
+<pre>
+STY addr
+STY dp
+STY dp, X
+</pre>
+==== Cycle Penalties ====
+* STY takes one additional cycle when the index registers are 16 bits wide, in all [[addressing modes]].
+* In both [[direct page addressing]] modes only, STY takes another additional cycle if the low byte of the [[direct page register]] is nonzero.
 === See Also ===
+* [[LDY]]
 * [[STA]]
 * [[STX]]
 * [[STZ]]
+* [[TYA]]
+* [[TYX]]
 === External Links ===
-* [[Eyes & Lichty]] page on STY: https://archive.org/details/0893037893ProgrammingThe65816/page/n532
+* [[Eyes & Lichty]], [https://archive.org/details/0893037893ProgrammingThe65816/page/506 page 506] on STY
-* [[Labiak]] page on STY: https://archive.org/details/Programming_the_65816/page/n197
+* [[Labiak]], [https://archive.org/details/Programming_the_65816/page/n197 page 187] on STY
-* [[MCS6500 Manual]] page on STY: https://archive.org/details/mos_microcomputers_programming_manual/page/n115
+* 7.3 on [[MCS6500 Manual]], [https://archive.org/details/mos_microcomputers_programming_manual/page/n115 page 97] on STY
-* [[Carr]] page on STY: https://archive.org/details/6502UsersManual/page/n287
+* [[Carr]], [https://archive.org/details/6502UsersManual/page/n287 page 274] on STY
-* [[Leventhal]] page on STY: https://archive.org/details/6502-assembly-language-programming/page/n147
+* [[Leventhal]], [https://archive.org/details/6502-assembly-language-programming/page/n147 page 3-98] on STY
 * snes9x implementation of STY: https://github.com/snes9xgit/snes9x/blob/master/cpuops.cpp#L1302
 * undisbeliever on STY: https://undisbeliever.net/snesdev/65816-opcodes.html#sty-store-index-register-y-to-memory
+* Pickens, John. http://www.6502.org/tutorials/6502opcodes.html#STY
 [[Category:ASM]]
 [[Category:Group Three Instructions]]
 [[Category:Inherited from 6502]]
+[[Category:Load/Store Instructions]]