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General Form



IDLE ; /* (a) */

Instruction Length

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

Functional Description

Typically, the Idle instruction is part of a sequence to place the Blackfin processor in a quiescent state so that the external system can switch between core clock frequencies.

The IDLE instruction requests an idle state by setting the idle_req bit in SEQSTAT register. Setting the idle_req bit precedes placing the Blackfin processor in a quiescent state. If you intend to place the processor in Idle mode, the IDLE instruction must immediately precede an SSYNC instruction.

The first instruction following the SSYNC is the first instruction to execute when the processor recovers from Idle mode.

The Idle instruction is the only way to set the idle_req bit in SEQSTAT. The architecture does not support explicit writes to SEQSTAT.

Flags Affected


Required Mode

The Idle 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

This instruction cannot be issued in parallel with other instructions.


idle ;

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Special Applications