LSR (Logical Shift Right)¶

[operand] = [operand] >> 1

LSR shifts all the bits of an operand one place to the right.

The Carry flag is set to the value of the least significant bit that is shifted out of the operand. Before the shift, the Carry flag has no effect on the operation.

LSR can operate on both memory locations and the accumulator register (A). When used on memory, the operand is the value stored at the specified memory address.

Addressing Modes¶

LSR supports the following addressing modes:

Mode	Syntax	Bytes	Cycles
Implied	LSR A	`4A`	2
Zero Page	LSR zp	`46 nn`	5
Zero Page + X	LSR zp,X	`56 nn`	6
Absolute	LSR addr	`4E ll hh`	6
Absolute + X	LSR addr,X	`5E ll hh`	7

Flags Affected¶

N (Negative) – Set to 0, since the most significant bit is always 0.
Z (Zero) – Set if the result is zero; otherwise, it is cleared.
C (Carry) – Set to the value of the least significant bit before it is shifted out.

Examples¶

Shift Accumulator Right¶

    LDA #5    ; load A with binary 00000101
    LSR A     ; A now contains binary 00000010, C is set to 1

Shift Memory Right¶

    LDX #$10  ; load X with 16
    LSR $00,X ; Shift the value at address $0010 right