We've just updated MediaWiki and its underlying software. If anything doesn't look or work quite right, please mention it to us. --RanAS

MVP: Difference between revisions

From SnesLab
Jump to: navigation, search
(→‎Execution Sequence: destination bank)
(→‎External Links: de'nd page number)
Line 62: Line 62:


=== External Links ===
=== External Links ===
* [[Eyes & Lichty]] page 468 on MVP: https://archive.org/details/0893037893ProgrammingThe65816/page/n494
* [[Eyes & Lichty]] page 468 on MVP: https://archive.org/details/0893037893ProgrammingThe65816/page/468
* [[Labiak]] page 154 on MVP: https://archive.org/details/Programming_the_65816/page/n164
* [[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
* snes9x implementation of MVP: https://github.com/snes9xgit/snes9x/blob/master/cpuops.cpp#L3077

Revision as of 18:31, 31 July 2024

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

MVP works even in emulation mode.

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. The destination bank is written to DBR.

See Also

External Links