SAX

SAX (short for "Store Accumulator AND X") is the mnemonic for the illegal opcode machine language instruction which stores the bitwise AND of the accumulator and the X index register at the RAM or I/O address specified. The contents of the both the accumulator and the X index register remains unchanged through the operation.

This illegal opcode is a combination of two operations with the same addressing mode: STA, STX

Function: {addr} = A & X

Addressing modes

Opcode		Addressing mode	Assembler format	Length in bytes	Number of cycles
Dec	Hex
143	8F	Absolute	SAX nnnn	3	4
135	87	Zeropage	SAX nn	2	3
151	97	Zeropage,Y	SAX nn,Y	2	4
131	83	Indexed-indirect	SAX (nn,X)	2	6

SAX supports the 4 different 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.

CPU flags

SAX does not affect any of the CPU's status flags.

Links

• NMOS 6510 Unintended Opcodes (No More Secrets)