BPL: Difference between revisions

Latest revision as of 22:39, 15 August 2024


Basic Info
Addressing Mode	Opcode	Length	Speed
Program Counter Relative	10	2 bytes	2 cycles*


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

BPL (Branch if PLus) is a 65x instruction that performs a jump if the negative flag is clear. Note that zero is considered positive in the 65x architecture, so this instruction's behavior might be more accurately be described as "branch if non-negative."

The signed displacement of the target address can range from -128 to 127.

If the negative flag is set, control simply falls through to the instruction following BPL.

No flags are affected.

Syntax

BPL nearlabel

Cycle Penalties

BPL takes one additional cycle if the branch is taken
BPL takes another extra cycle if that branch taken crosses a page boundary in emulation mode.

External Links

Eyes & Lichty, page 434 on BPL
Labiak, page 124 on BPL
4.1.2.2 on MCS6500 Manual, page 40 on BPL
Carr, page 251 on BPL
Leventhal, page 3-48 on BPL
snes9x implementation of BPL: https://github.com/snes9xgit/snes9x/blob/master/cpuops.cpp#L1385

@@ Line 7: / Line 7: @@
 |'''Speed'''
 |+
-|relative
+|[[Program Counter Relative]]
 |10
-|2 byte
+|2 bytes
-|3 cycles
+|2 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 35: / Line 35: @@
 |}
 '''BPL''' (Branch if PLus) is a 65x instruction that performs a jump if the [[negative flag]] is clear.  Note that zero is considered positive in the 65x architecture, so this instruction's behavior might be more accurately be described as "branch if non-negative."
+The signed displacement of the target address can range from -128 to 127.
+If the negative flag is set, control simply falls through to the instruction following BPL.
+No flags are affected.
+==== Syntax ====
+<pre>
+BPL nearlabel
+</pre>
+==== Cycle Penalties ====
+* BPL takes one additional cycle if the branch is taken
+* BPL takes another extra cycle if that branch taken crosses a page boundary in [[emulation mode]].
 === See Also ===
+* [[BMI]]
 * [[BNE]]
 * [[BPL (SPC700)]]
@@ Line 43: / Line 59: @@
 === External Links ===
-* [[Eyes & Lichty]] page on BPL: https://archive.org/details/0893037893ProgrammingThe65816/page/n460
+* [[Eyes & Lichty]], [https://archive.org/details/0893037893ProgrammingThe65816/page/434 page 434] on BPL
-* [[Labiak]] page on BPL: https://archive.org/details/Programming_the_65816/page/n133
+* [[Labiak]], [https://archive.org/details/Programming_the_65816/page/n134 page 124] on BPL
-* [[MCS6500 Manual]] page on BPL: https://archive.org/details/mos_microcomputers_programming_manual/page/n55
+* 4.1.2.2 on [[MCS6500 Manual]], [https://archive.org/details/mos_microcomputers_programming_manual/page/n55 page 40] on BPL
-* [[Carr]] page on BPL: https://archive.org/details/6502UsersManual/page/n264
+* [[Carr]], [https://archive.org/details/6502UsersManual/page/n264 page 251] on BPL
-* [[Leventhal]] page on BPL: https://archive.org/details/6502-assembly-language-programming/page/n97
+* [[Leventhal]], [https://archive.org/details/6502-assembly-language-programming/page/n97 page 3-48] on BPL
 * snes9x implementation of BPL: https://github.com/snes9xgit/snes9x/blob/master/cpuops.cpp#L1385
 [[Category:ASM]]
 [[Category:Inherited from 6502]]
+[[Category:Conditional Branches]]
+[[Category:Two-byte Instructions]]