BRA: Difference between revisions

Latest revision as of 03:38, 8 August 2024


Basic Info
Addressing Mode	Opcode	Length	Speed
Program Counter Relative	80	2 bytes	3 cycles*


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

BRA (BRanch Always) is a 65c816 instruction that performs an unconditional jump. The signed displacement ranges from -128 to 127. The displacement is sign-extended to 16 bits and added to the program counter. The displacement is measured from the instruction following BRA.

BRA is relocatable. No flags are affected.

Syntax

BRA nearlabel

BRA has the same timing as other branches, it just has no "branch not taken" case.

Cycle Penalty

BRA takes one additional cycle if the branch crosses a page boundary in emulation mode.

External Links

Eyes & Lichty, page 435 on BRA
Labiak, page 125 on BRA
snes9x implementation of BRA: https://github.com/snes9xgit/snes9x/blob/master/cpuops.cpp#L1390
Clark, Bruce. http://www.6502.org/tutorials/65c816opcodes.html#6.2.1.1

@@ Line 1: / Line 1: @@
-'''BRA''' is a [[65c816]] instruction that performs an unconditional jump.
+{| class="wikitable" style="float:right;clear:right;width:40%"
+!colspan="8"|Basic Info
+|+
+|'''Addressing Mode'''
+|'''Opcode'''
+|'''Length'''
+|'''Speed'''
+|+
+|[[Program Counter Relative]]
+|80
+|2 bytes
+|3 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 22: / Line 34: @@
 |.
 |}
+'''BRA''' (BRanch Always) is a [[65c816]] instruction that performs an unconditional jump.  The signed displacement ranges from -128 to 127.  The displacement is sign-extended to 16 bits and added to the [[program counter]].  The displacement is measured from the instruction following BRA.
+BRA is relocatable.  No flags are affected.
+==== Syntax ====
+<pre>
+BRA nearlabel
+</pre>
+BRA has the same timing as other branches, it just has no "branch not taken" case.
+===== Cycle Penalty =====
+* BRA takes one additional cycle if the branch crosses a page boundary in [[emulation mode]].
+=== See Also ===
+* [[JMP]]
+* [[BRA (Super FX)]]
+=== External Links ===
+* [[Eyes & Lichty]], [https://archive.org/details/0893037893ProgrammingThe65816/page/435 page 435] on BRA
+* [[Labiak]], [https://archive.org/details/Programming_the_65816/page/n135 page 125] on BRA
+* snes9x implementation of BRA: https://github.com/snes9xgit/snes9x/blob/master/cpuops.cpp#L1390
+* Clark, Bruce. http://www.6502.org/tutorials/65c816opcodes.html#6.2.1.1
 [[Category:ASM]]
+[[Category:65c02 additions]]
+[[Category:Unconditional Branches]]
+[[Category:Two-byte Instructions]]
+[[Category:Relocatable Instructions]]
+[[Category:Single Admode Mnemonics]]