ROR: Difference between revisions

Latest revision as of 19:24, 8 January 2024


Basic Info
Addressing Mode	Opcode	Length	Speed
Accumulator	6A	1 byte	2 cycles
Absolute	6E	3 bytes	6 cycles*
Direct Page	66	2 bytes	5 cycles*
absolute indexed by X	7E	3 bytes	7 cycles*
direct page indexed by X	76	2 bytes	6 cycles*


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

ROR (Rotate Right) is a 65x instruction that rotates a value and the carry flag right one bit. The least significant bit is shifted into the carry flag. The carry flag is shifted into the most significant bit.

Cycle Penalties

Except in accumulator addressing, ROR takes two extra cycles when the accumulator is 16 bits wide.
In direct page addressing modes, ROR takes another extra cycle if the low byte of the direct page register is nonzero.

External Links

Eyes & Lichty page 491, on ROR: https://archive.org/details/0893037893ProgrammingThe65816/page/n517
lbid, page 191, before & after diagram on ROR: https://archive.org/details/0893037893ProgrammingThe65816/page/n217
Labiak page 175 on ROR: https://archive.org/details/Programming_the_65816/page/n185
MCS6500 Manual page 150 on ROR: https://archive.org/details/mos_microcomputers_programming_manual/page/n171
Carr page 269 on ROR: https://archive.org/details/6502UsersManual/page/n282
Leventhal page 3-87 on ROR: https://archive.org/details/6502-assembly-language-programming/page/n136
snes9x implementation of ROR: https://github.com/snes9xgit/snes9x/blob/master/cpuops.cpp#L1070
undisbeliever on ROR: https://undisbeliever.net/snesdev/65816-opcodes.html#ror-rotate-right

@@ Line 1: / Line 1: @@
-'''ROR''' (Rotate Right) is a 65x instruction that rotates a value and the [[carry flag]] right one bit.  The least significant bit is shifted into the carry flag.  The carry flag is shifted into the most significant bit.
+{| class="wikitable" style="float:right;clear:right;width:40%"
-{| class="wikitable" style="float:right;clear:right;width:30%"
 !colspan="8"|Basic Info
 |+
@@ Line 9: / Line 7: @@
 |'''Speed'''
 |+
-|accumulator
+|[[Accumulator Addressing|Accumulator]]
 |6A
 |1 byte
 |2 cycles
 |+
-|absolute
+|[[Absolute]]
 |6E
 |3 bytes
-|6 cycles
+|6 cycles*
 |+
-|direct page
+|[[Direct Page Addressing|Direct Page]]
 |66
 |2 bytes
-|5 cycles
+|5 cycles*
 |+
 |absolute indexed by X
 |7E
 |3 bytes
-|7 cycles
+|7 cycles*
 |+
 |direct page indexed by X
 |76
 |2 bytes
-|6 cycles
+|6 cycles*
 |}
 {| class="wikitable" style="float:right;clear:right;width:30%"
-!colspan="9"|Flags Clobbered
+!colspan="9"|Flags Affected
 |+
-|N
+|[[N Flag|N]]
-|V
+|[[V Flag|V]]
-|M
+|[[M Flag|M]]
-|X
+|[[X Flag|X]]
-|D
+|[[D Flag|D]]
-|I
+|[[I Flag|I]]
-|Z
+|[[Z Flag|Z]]
-|C
+|[[C Flag|C]]
 |+
 |
@@ Line 56: / Line 54: @@
 |
 |}
+'''ROR''' (Rotate Right) is a 65x instruction that rotates a value and the [[carry flag]] right one bit.  The least significant bit is shifted into the carry flag.  The carry flag is shifted into the most significant bit.
+===== Cycle Penalties =====
+* Except in [[accumulator addressing]], ROR takes two extra cycles when the accumulator is 16 bits wide.
+* In [[direct page addressing]] modes, ROR takes another extra cycle if the low byte of the [[direct page register]] is nonzero.
 === See Also ===
 * [[ROL]]
+* [[ROR (SPC700)]]
+* [[ROR (Super FX)]]
 === External Links ===
-* [[Eyes & Lichty]] page on ROR: https://archive.org/details/0893037893ProgrammingThe65816/page/n517
+* [[Eyes & Lichty]] page 491, on ROR: https://archive.org/details/0893037893ProgrammingThe65816/page/n517
-* [[Labiak]] page on ROR: https://archive.org/details/Programming_the_65816/page/n185
+* lbid, page 191, before & after diagram on ROR: https://archive.org/details/0893037893ProgrammingThe65816/page/n217
-* [[MCS6500 Manual]] page on ROR: https://archive.org/details/mos_microcomputers_programming_manual/page/n171
+* [[Labiak]] page 175 on ROR: https://archive.org/details/Programming_the_65816/page/n185
-* [[Carr]] page on ROR: https://archive.org/details/6502UsersManual/page/n282
+* [[MCS6500 Manual]] page 150 on ROR: https://archive.org/details/mos_microcomputers_programming_manual/page/n171
-* [[Leventhal]] page on ROR: https://archive.org/details/6502-assembly-language-programming/page/n136
+* [[Carr]] page 269 on ROR: https://archive.org/details/6502UsersManual/page/n282
+* [[Leventhal]] page 3-87 on ROR: https://archive.org/details/6502-assembly-language-programming/page/n136
 * snes9x implementation of ROR: https://github.com/snes9xgit/snes9x/blob/master/cpuops.cpp#L1070
+* undisbeliever on ROR: https://undisbeliever.net/snesdev/65816-opcodes.html#ror-rotate-right
 [[Category:ASM]]