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MVN

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Basic Info
Addressing Mode Opcode Length Speed
Block Move 54 3 bytes 7 cycles per byte moved
mvn.png
Flags Affected
N V M X D I Z C
. . . . . . . .

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

In Eyes & Lichty, the "N" in the mnemonic stands for "Next" not "Negative."

MVN works even in emulation mode, but the blocks must be in the zeropage.

Parameters

  • the X index register specifies the starting (lowest) source address of the block
  • the Y index register specifies the starting (lowest) 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 incremented
  • C is decremented

If interrupted, the current byte finishes copying before servicing the interrupt. The destination bank is written to DBR.

Assembler Syntax

Asar:

MVN srds

where "sr" is the source bank, and "ds" is the destination bank, with nothing in between them.[1]

See Also

External Links

References

  1. https://github.com/InsaneFirebat/sm_practice_hack/blob/master/src/custompresets.asm#L260