DBNZ (SPC700): Difference between revisions

Revision as of 17:16, 24 July 2023


Basic Info
Addressing Mode	Opcode	Length	Speed
Direct Page / Program Counter Relative	6E	3 bytes	when condition is false: 5 cycles when condition is true: 7 cycles
Implied (type 1) / Program Counter Relative	FE	2 bytes	when condition is false: 4 cycles when condition is true: 6 cycles


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

DBNZ is an SPC700 instruction that decrements a direct page location or the Y index register and then jumps if that value is nonzero. The direct page index is the first operand and also the first byte immediately following the opcode. The relative branch offset is the second operand, the second byte following the opcode.^[2]

References

Official Super Nintendo development manual on DBNZ: Appendix C-8 of Book I
anomie's SPC700 doc

@@ Line 42: / Line 42: @@
 |}
-'''DBNZ''' is an [[SPC700]] instruction that decrements a [[direct page]] location or the [[Y index register]] and then jumps if that value is nonzero.
+'''DBNZ''' is an [[SPC700]] instruction that decrements a [[direct page]] location or the [[Y index register]] and then jumps if that value is nonzero.  The direct page index is the first operand and also the first byte immediately following the opcode.  The relative branch offset is the second operand, the second byte following the opcode.<sup>[2]</sup>
 === See Also ===
@@ Line 48: / Line 48: @@
 * [[JNZ]]
-=== External Links ===
+=== References ===
-* Official Super Nintendo development manual on DBNZ: [https://archive.org/details/SNESDevManual/book1/page/n234 Appendix C-8 of Book I]
+# Official Super Nintendo development manual on DBNZ: [https://archive.org/details/SNESDevManual/book1/page/n234 Appendix C-8 of Book I]
+# [https://www.romhacking.net/documents/197 anomie's SPC700 doc]
 [[Category:ASM]]
 [[Category:SPC700]]
 [[Category:Branching Commands]]