MVP: Difference between revisions

Revision as of 10:39, 15 July 2024


Basic Info
Addressing Mode	Opcode	Length	Speed
Block Move	44	3 bytes	7 cycles per byte moved


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

MVP (Block Move Positive) is a 65c816 instruction that copies a contiguous block of memory. It is intended to copy a block from a lower address to a higher address (moving it in the positive direction). No flags are affected.

In Eyes & Lichty, the "P" in the mnemonic stands for "Previous" not "Positive."

Parameters

the X index register specifies the ending (highest) source address of the block
the Y index register specifies the ending (highest) destination address of the block
the C double accumulator specifies the length of the block in bytes minus one
the first operand byte specifies the destination bank the block will be in
the second operand byte specifies the source bank the block starts out in

Execution Sequence

The following loop is repeated until the value in the C double accumulator is $FFFF:

one byte is copied from the address in X to the address in Y
both X and Y are decremented
C is decremented

If interrupted, the current byte finishes copying before servicing the interrupt.

External Links

Eyes & Lichty page 468 on MVP: https://archive.org/details/0893037893ProgrammingThe65816/page/n494
Labiak page 154 on MVP: https://archive.org/details/Programming_the_65816/page/n164
snes9x implementation of MVP: https://github.com/snes9xgit/snes9x/blob/master/cpuops.cpp#L3077
undisbeliever on MVP: https://undisbeliever.net/snesdev/65816-opcodes.html#mvp-block-move-previous

@@ Line 53: / Line 53: @@
 * both X and Y are decremented
 * C is decremented
+If interrupted, the current byte finishes copying before servicing the interrupt.
 === See Also ===