LDY (short for "LoaD Y") is the mnemonic for a machine language instruction which retrieves a copy from the specified RAM or I/O address, and stores it in the Y index register. The content of the memory location is not affected by the operation.
Addressing modes[edit | edit source]
LDY supports the five addressing modes shown in the table at right.
In the assembler formats listed, nn represents a single-byte (8-bit) figure, and nnnn is a two-byte (16-bit) address.
With some addressing forms (marked with an asterisk, *, in the "Number of cycles" column) the execution time for LDY depends on the circumstances: In cases where the indexing requires the CPU to "reach across" a page boundary from the base address, the execution time is 1 cycle longer than listed here.
CPU flags[edit | edit source]
LDY affects 2 of the CPU's status flags: