BBS (SPC700): Difference between revisions

Latest revision as of 07:53, 18 December 2023


Basic Info
Addressing Mode	Opcode	Length	Speed
Direct Page Bit Relative	03	3 bytes	when condition false: 5 cycles when condition true: 7 cycles
Direct Page Bit Relative	23	3 bytes	when condition false: 5 cycles when condition true: 7 cycles
Direct Page Bit Relative	43	3 bytes	when condition false: 5 cycles when condition true: 7 cycles
Direct Page Bit Relative	63	3 bytes	when condition false: 5 cycles when condition true: 7 cycles
Direct Page Bit Relative	83	3 bytes	when condition false: 5 cycles when condition true: 7 cycles
Direct Page Bit Relative	A3	3 bytes	when condition false: 5 cycles when condition true: 7 cycles
Direct Page Bit Relative	C3	3 bytes	when condition false: 5 cycles when condition true: 7 cycles
Direct Page Bit Relative	E3	3 bytes	when condition false: 5 cycles when condition true: 7 cycles


Flags Affected
N	V	P	B	H	I	Z	C
.	.	.	.	.	.	.	.

BBS (Branch on Bit Set) is an SPC700 instruction that performs a branch when a bit in the direct page is set. The index to the direct page byte that bit lives in is the first operand byte. Which bit within that byte is a specified by the top 3 bits of the opcode. The target relative address to jump to is the second operand byte.

In assembly source, the two operands appear in the same order that they do in the instruction stream.

References

Table C-15, Appendix C-8 of Book I of the official Super Nintendo development manual

@@ Line 1: / Line 1: @@
-'''BBS''' (Branch on Bit Set) is an [[SPC700]] that performs a branch when the [[direct page flag]] is set.
+{| class="wikitable" style="float:right;clear:right;width:50%"
-{| class="wikitable" style="float:right;clear:right;width:30%"
 !colspan="8"|Basic Info
 |+
@@ Line 9: / Line 7: @@
 |'''Speed'''
 |+
-|
+|[[Direct Page Bit Relative]]
-|x3
+|03
+|3 bytes
+|when condition false: 5 cycles
+when condition true: 7 cycles
+|+
+|[[Direct Page Bit Relative]]
+|23
+|3 bytes
+|when condition false: 5 cycles
+when condition true: 7 cycles
+|+
+|[[Direct Page Bit Relative]]
+|43
+|3 bytes
+|when condition false: 5 cycles
+when condition true: 7 cycles
+|+
+|[[Direct Page Bit Relative]]
+|63
+|3 bytes
+|when condition false: 5 cycles
+when condition true: 7 cycles
+|+
+|[[Direct Page Bit Relative]]
+|83
 |3 bytes
-|5 or 7 cycles
+|when condition false: 5 cycles
+when condition true: 7 cycles
+|+
+|[[Direct Page Bit Relative]]
+|A3
+|3 bytes
+|when condition false: 5 cycles
+when condition true: 7 cycles
+|+
+|[[Direct Page Bit Relative]]
+|C3
+|3 bytes
+|when condition false: 5 cycles
+when condition true: 7 cycles
+|+
+|[[Direct Page Bit Relative]]
+|E3
+|3 bytes
+|when condition false: 5 cycles
+when condition true: 7 cycles
 |}
 {| class="wikitable" style="float:right;clear:right;width:30%"
-!colspan="8"|Flags Clobbered
+!colspan="8"|Flags Affected
 |+
-|N
+|[[Negative Flag|N]]
-|V
+|[[Overflow Flag|V]]
-|P
+|[[Direct Page Flag|P]]
-|B
+|[[Break Flag|B]]
-|H
+|[[Half-Carry Flag|H]]
-|I
+|[[Interrupt Enable Flag|I]]
-|Z
+|[[Zero Flag|Z]]
-|C
+|[[Carry Flag|C]]
 |+
 |.
@@ Line 36: / Line 77: @@
 |.
 |}
+'''BBS''' (Branch on Bit Set) is an [[SPC700]] instruction that performs a branch when a bit in the [[direct page]] is set.  The index to the direct page byte that bit lives in is the first operand byte.  Which bit within that byte is a specified by the top 3 bits of the opcode.  The target relative address to jump to is the second operand byte.
+In assembly source, the two operands appear in the same order that they do in the instruction stream.
 === See Also ===
-* [[BBS]]
+* [[BBC]]
 === References ===
-* [https://archive.org/details/SNESDevManual/book1/page/n233 Appendix C-8 of Book I] of the official Super Nintendo development manual
+* Table C-15,  [https://archive.org/details/SNESDevManual/book1/page/n233 Appendix C-8 of Book I] of the official Super Nintendo development manual
 [[Category:ASM]]
 [[Category:SPC700]]
 [[Category:Branching Commands]]