Svc; Wfe - ST STM32F0 Series Programming Manual

PM0215
3.7.10

SVC

Supervisor call.
Syntax
SVC #imm
where: 'imm' is an integer in the range 0-255.
Operation
The SVC instruction causes the SVC exception. imm is ignored by the processor. It can be
retrieved by the exception handler to determine what service is being requested.
Restrictions
Condition flags
This instruction does not change the flags.
Examples
SVC 0x32
3.7.11

WFE

Wait for event. WFE is a hint instruction.
Syntax
WFE
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
WFE is intended for power saving only. When writing software assume that WFE might
behave as NOP.
Restrictions
Condition flags
This instruction does not change the flags.
Examples
WFE ; Wait for event
: None
; Supervisor Call (SVC handler can extract the immediate value
; by locating it via the stacked PC)
28.
: None
Doc ID 022979 Rev 1
The STM32 Cortex-M0 instruction set
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