The MVN & MVP instructions moves/copies a block of memory from one location to another.

The source, destination and length of the block are taken from the X, Y & C registers.

The source address is in X, the destination address is in Y.

The length of the block minus 1 is in the C double accumulator. So if you are moving 42 bytes then C should have 41.

The two bytes of the operand consists of the source bank in the first byte and the destination bank in the second.

Processor modes

These instructions should be run in 16-bit native mode. If the index registers are in 8-bit mode (x=1) or the processor is in 6502 emulation mode (e=1) then the blocks specified will be in zero page due to the high byte of the index registers will be 0.

Interrupts

If a block move instruction is interrupted, it may be resumed automatically when RTI is executed by the handler, as long as the registers are left intact. The address pushed to the stack when it is interrupted is the address of the block move instruction so it resumes where it left off. The byte currently being moved will complete first before the interrupt is serviced.

MVN

MVN copies a block from the start of the source block to the start of the destination block.

The source and destination addresses need to point to the first byte of each block to be moved.

When execution is complete, the C accumulator will be &FFFF X & Y will point to the byte after the end of the source & destination blocks respectively.

MVP - Block Move Previous

MVP copies a block from the end of the source block to the end of the destination block.

The source and destination addresses need to point to the last byte of each block to be moved.

When execution is complete, the C accumulator will be &FFFF X & Y will point to the byte before the start of the source & destination blocks respectively.