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Disable Interrupts

General Form



CLI Dreg ; /* previous state of IMASK moved to Dreg (a) */

Syntax Terminology


Instruction Length

In the syntax, comment (a) identifies 16-bit instruction length.

Functional Description

The Disable Interrupts instruction globally disables general interrupts by setting IMASK to all zeros. In addition, the instruction copies the previous contents of IMASK into a user-specified register in order to save the state of the interrupt system.

The Disable Interrupts instruction does not mask NMI, reset, exceptions and emulation.

Flags Affected


Required Mode

The Disable Interrupts instruction executes only in Supervisor mode. If execution is attempted in User mode, the instruction produces an Illegal Use of Protected Resource exception.

Parallel Issue

The Disable Interrupts instruction cannot be issued in parallel with other instructions.


cli r3 ;

Also See

Special Applications

This instruction is often issued immediately before an IDLE instruction.