NOP

NOP

No Operation (PREFIX)

Operation

Assembler Syntax

no operation

NOP

NOP

Description

NOP

This instruction is encoded as a one-word prefix inside the set, or alone. If the NOP is the only instruction in the execution set, it takes one cycle to execute although no operation is done. This is useful in case delays are needed in a program for various reasons (for example, to account for pipeline delays). The NOP instruction is not dispatched to any execution unit. As a prefix, it is identified by the dispatcher and is not dispatched further.

If grouped with other instructions (as an intra-group NOP), it functions as a program place-holder.

In a few isolated cases, the assembler adds this instruction inside an execution set to help arrange the instructions within that set for proper dispatching. These cases are implementation-dependent. The assembler issues a warning to make the user aware of the event.

Status and conditions that Affect Instruction

None.

Status and Conditions Changed by Instruction

None.

Example

nop

Instruction Formats and Opcodes

Instruction

Words

Cycles

Type

NOP

1

1

4

Opcode

15

8

7

0

1 0 0 1 0 0 0 0 1 1 0 0 0 0 0 0

SC140 DSP Core Reference Manual

A-333

Page 647
Image 647
Freescale Semiconductor SC140 specifications Nop, No Operation Prefix, No operation