MOVW (SPC700): Difference between revisions

Latest revision as of 11:52, 28 November 2023


Basic Info
Direction	Addressing Mode	Opcode	Length	Speed
to YA	Direct Page	BA	2 bytes	5 cycles
from YA	Direct Page	DA	2 bytes	4 cycles


Flags Affected
Direction	N	V	P	B	H	I	Z	C
to YA		.	.	.	.	.
from YA	.	.	.	.	.	.	.	.

MOVW (Move Word) is an SPC700 instruction that moves a 16-bit direct page value to or from the YA register. There are no variations of MOVW that do not operate on YA. MOVW performs a read cycle on the low byte of the destination, but not the source.^[2]

The operands are stored in the instruction stream in the opposite order they appear in the assembler source. In the assembler source, the operand on the right is the source and the operand on the left is the destination.

Example

From the IPL ROM,

MOVW YA, $F6	; load the byte at direct page location $F6 into A and the byte at direct page location $F7 into Y
MOVW $00, YA	; store the value in Y to direct page location $01 and the value in A to direct page location $00

References

Official Super Nintendo development manual on MOVW: Table C-11 in Appendix C-8 of Book I
anomie's SPC700 doc

@@ Line 1: / Line 1: @@
-'''MOVW''' is an [[SPC700]] instruction that moves a value to or from [[YA]].
+{| class="wikitable" style="float:right;clear:right;width:40%"
+!colspan="5"|Basic Info
-{| class="wikitable" style="float:right;clear:right;width:30%"
-!colspan="8"|Basic Info (to YA)
 |+
+|'''Direction'''
 |'''Addressing Mode'''
 |'''Opcode'''
@@ Line 9: / Line 8: @@
 |'''Speed'''
 |+
-|
+|to YA
+|[[Direct Page Addressing | Direct Page]]
 |BA
 |2 bytes
 |5 cycles
+|+
+|from YA
+|[[Direct Page Addressing | Direct Page]]
+|DA
+|2 bytes
+|4 cycles
 |}
 {| class="wikitable" style="float:right;clear:right;width:30%"
-!colspan="8"|Flags Clobbered (to YA)
+!colspan="9"|Flags Affected
 |+
-|N
+|Direction
-|V
+|[[Negative Flag|N]]
-|P
+|[[Overflow Flag|V]]
-|B
+|[[Direct Page Flag|P]]
-|H
+|[[Break Flag|B]]
-|I
+|[[Half-Carry Flag|H]]
-|Z
+|[[Interrupt Enable Flag|I]]
-|C
+|[[Zero Flag|Z]]
+|[[Carry Flag|C]]
 |+
+|to YA
 |
 |.
@@ Line 35: / Line 43: @@
 |
 |
-|}
-{| class="wikitable" style="float:right;clear:right;width:30%"
-!colspan="8"|Basic Info (from YA)
-|+
-|'''Addressing Mode'''
-|'''Opcode'''
-|'''Length'''
-|'''Speed'''
-|+
-|
-|DA
-|2 bytes
-|4 cycles
-|}
-{| class="wikitable" style="float:right;clear:right;width:30%"
-!colspan="8"|Flags Clobbered (from YA)
-|+
-|N
-|V
-|P
-|B
-|H
-|I
-|Z
-|C
 |+
+|from YA
 |.
 |.
@@ Line 72: / Line 54: @@
 |.
 |}
+'''MOVW''' (Move Word) is an [[SPC700]] instruction that moves a 16-bit [[direct page]] value to or from the [[YA]] register.  There are no variations of MOVW that do not operate on YA.  MOVW performs a read cycle on the low byte of the destination, but not the source.<sup>[2]</sup>
+The operands are stored in the instruction stream in the opposite order they appear in the assembler source. In the assembler source, the operand on the right is the source and the operand on the left is the destination.
+=== Example ===
+From the [[IPL ROM]],
+<pre>
+MOVW YA, $F6	; load the byte at direct page location $F6 into A and the byte at direct page location $F7 into Y
+MOVW $00, YA	; store the value in Y to direct page location $01 and the value in A to direct page location $00
+</pre>
 === See Also ===
 * [[MOV]]
+* [[MOV1]]
+* [[ADDW]]
+* [[SUBW]]
+* [[CMPW]]
+=== References ===
+# Official Super Nintendo development manual on MOVW: Table C-11 in [https://archive.org/details/SNESDevManual/book1/page/n233 Appendix C-8 of Book I]
+# [https://www.romhacking.net/documents/197 anomie's SPC700 doc]
 [[Category:ASM]]
 [[Category:SPC700]]
 [[Category:16-bit Data Transmission Commands]]
+[[Category:Two-byte Instructions]]