STY Instruction (Store Index Register Y to Memory)

Writes the value of index register Y to the specified address in memory.

STY Overloads

Opcode	Syntax	Addressing mode	Bytes	Cycles	Notes
84	STY dp	DP.	2	3	1, 2
94	STY dp, X	DP. Idx X	2	4	1, 2
8C	STY abs	Abs.	3	4	1

Notes

Add 1 cycle when the index flag is clear.
Add 1 cycle when the direct page start address is not on a page boundary.

Flag changes

--------

This instruction does not change the status flags.

Explanation

The STY instruction writes the value of index register Y to memory according to the addressing mode specified by the opcode.
When the index flag in the status register is clear, it writes 16-bit data; when the index flag is set, it writes 8-bit data.
Data is written in little-endian order. That is, in memory the low byte always comes first.

Examples

Saving a value

    STY $12         ; save Y to $12

The only indexed mode available for STY is dp,X.