PM0214 datasheet(176/245 Pages) STMICROELECTRONICS

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The STM32 Cortex-M4 instruction set

PM0214

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DocID022708 Rev 4

3.11.10

SVC

Supervisor Call.

Syntax

SVC{cond} #imm

where:

•

‘cond’ is an optional condition code, see Conditional execution on page 64.

•

‘imm’ is an expression evaluating to an integer in the range 0-255 (8-bit value).

Operation

The SVC instruction causes the SVC exception. imm is ignored by the processor. If

required, it can be retrieved by the exception handler to determine what service is being

requested.

Condition flags

This instruction does not change the flags.

Examples

SVC

0x32

; Supervisor Call (SVC handler can extract the immediate

value

; by locating it via the stacked PC)

3.11.11

WFE

Wait For Event. WFE is a hint instruction.

Syntax

WFE{cond}

where: ‘cond’ is an optional condition code, see Conditional execution on page 64.

Operation

If the event register is 0, WFE suspends execution until one of the following events occurs:

•

An exception, unless masked by exception mask registers or the current priority level

•

An exception enters Pending state, if SEVONPEND in System Control Register is set

•

A Debug Entry request, if Debug is enabled

•

An event signaled by a peripheral or another processor in a multiprocessor system

using the SEV instruction.

If the event register is 1, WFE clears it to 0 and returns immediately.

For more information see Power management on page 46.

Condition flags

This instruction does not change the flags.

Examples

WFE

; Wait for event

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