Intrinsic Functions for CPU Instructions

Functions that generate specific Cortex-M CPU Instructions. More...

Functions
void	__BKPT (uint8_t value)
	Set Breakpoint.
void	__CLREX (void)
	Remove the exclusive lock [not for Cortex-M0, Cortex-M0+, or SC000].
uint8_t	__CLZ (uint32_t value)
	Count leading zeros.
void	__DMB (void)
	Data Memory Barrier.
void	__DSB (void)
	Data Synchronization Barrier.
void	__ISB (void)
	Instruction Synchronization Barrier.
uint32_t	__LDA (volatile uint32_t *ptr)
	Load-Acquire (32 bit)
uint8_t	__LDAB (volatile uint8_t *ptr)
	Load-Acquire (8 bit)
uint32_t	__LDAEX (volatile uint32_t *ptr)
	Load-Acquire Exclusive (32 bit)
uint8_t	__LDAEXB (volatile uint32_t *ptr)
	Load-Acquire Exclusive (8 bit)
uint16_t	__LDAEXH (volatile uint32_t *ptr)
	Load-Acquire Exclusive (16 bit)
uint16_t	__LDAH (volatile uint16_t *ptr)
	Load-Acquire (16 bit)
uint8_t	__LDRBT (uint8_t ptr)
	LDRT Unprivileged (8 bit)
uint8_t	__LDREXB (volatile uint8_t *addr)
	LDR Exclusive (8 bit) [not for Cortex-M0, Cortex-M0+, or SC000].
uint16_t	__LDREXH (volatile uint16_t *addr)
	LDR Exclusive (16 bit) [not for Cortex-M0, Cortex-M0+, or SC000].
uint32_t	__LDREXW (volatile uint32_t *addr)
	LDR Exclusive (32 bit) [not for Cortex-M0, Cortex-M0+, or SC000].
uint16_t	__LDRHT (uint16_t ptr)
	LDRT Unprivileged (16 bit)
uint32_t	__LDRT (uint32_t ptr)
	LDRT Unprivileged (32 bit)
void	__NOP (void)
	No Operation.
uint32_t	__RBIT (uint32_t value)
	Reverse bit order of value.
uint32_t	__REV (uint32_t value)
	Reverse byte order (32 bit)
uint32_t	__REV16 (uint32_t value)
	Reverse byte order (16 bit)
int16_t	__REVSH (int16_t value)
	Reverse byte order (16 bit)
uint32_t	__ROR (uint32_t value, uint32_t shift)
	Rotate a value right by a number of bits.
uint32_t	__RRX (uint32_t value)
	Rotate Right with Extend (32 bit)
void	__SEV (void)
	Send Event.
int32_t	__SSAT (int32_t value, uint32_t sat)
	Signed Saturate.
void	__STL (uint32_t value, volatile uint32_t *ptr)
	Store-Release (32 bit)
void	__STLB (uint8_t value, volatile uint8_t *ptr)
	Store-Release (8 bit)
uint32_t	__STLEX (uint32_t value, volatile uint32_t *ptr)
	Store-Release Exclusive (32 bit)
uint32_t	__STLEXB (uint8_t value, volatile uint8_t *ptr)
	Store-Release Exclusive (8 bit)
uint32_t	__STLEXH (uint16_t value, volatile uint16_t *ptr)
	Store-Release Exclusive (16 bit)
void	__STLH (uint16_t value, volatile uint16_t *ptr)
	Store-Release (16 bit)
void	__STRBT (uint8_t value, uint8_t ptr)
	STRT Unprivileged (8 bit)
uint32_t	__STREXB (uint8_t value, volatile uint8_t *addr)
	STR Exclusive (8 bit) [not for Cortex-M0, Cortex-M0+, or SC000].
uint32_t	__STREXH (uint16_t value, volatile uint16_t *addr)
	STR Exclusive (16 bit) [not for Cortex-M0, Cortex-M0+, or SC000].
uint32_t	__STREXW (uint32_t value, volatile uint32_t *addr)
	STR Exclusive (32 bit) [not for Cortex-M0, Cortex-M0+, or SC000].
void	__STRHT (uint16_t value, uint16_t ptr)
	STRT Unprivileged (16 bit)
void	__STRT (uint32_t value, uint32_t ptr)
	STRT Unprivileged (32 bit)
uint32_t	__USAT (int32_t value, uint32_t sat)
	Unsigned Saturate.
void	__WFE (void)
	Wait For Event.
void	__WFI (void)
	Wait For Interrupt.

Description

Functions that generate specific Cortex-M CPU Instructions.

The following functions generate specific Cortex-M instructions that cannot be directly accessed by the C/C++ Compiler. Refer to the Cortex-M Generic User Guides for detailed information about these Cortex-M instructions.

Note

When using the Arm Compiler Version 5 Toolchain the following Intrinsic Functions for CPU Instructions are implemented using the Embedded Assembler. As the Embedded Assembler may cause side effects (Refer to Arm Compiler v5.xx User Guide - Using the Inline and Embedded Assemblers of the Arm Compiler for more information) it is possible to disable the following intrinsic functions and therefore the usage of the Embedded Assembler with the define __NO_EMBEDDED_ASM:

• __REV16
• __REVSH
• __RRX

Function Documentation

__BKPT()

void __BKPT

(

uint8_t

value

)

Set Breakpoint.

This function causes the processor to enter Debug state. Debug tools can use this to investigate system state when the instruction at a particular address is reached.

Parameters

[in]

value

is ignored by the processor. If required, a debugger can use it to obtain additional information about the breakpoint.

__CLREX()

void __CLREX

(

void

)

Remove the exclusive lock [not for Cortex-M0, Cortex-M0+, or SC000].

This function removes the exclusive lock which is created by LDREX [not for Cortex-M0, Cortex-M0+, or SC000].

__CLZ()

uint8_t __CLZ

(

uint32_t

value

)

Count leading zeros.

This function counts the number of leading zeros of a data value.

On Armv6-M (Cortex-M0, Cortex-M0+, and SC000) this function is not available as a core instruction instruction and thus __CLZ is implemented in software.

Parameters

[in]

value

Value to count the leading zeros

Returns

number of leading zeros in value

__DMB()

void __DMB

(

void

)

Data Memory Barrier.

This function ensures the apparent order of the explicit memory operations before and after the instruction, without ensuring their completion.

__DSB()

void __DSB

(

void

)

Data Synchronization Barrier.

This function acts as a special kind of Data Memory Barrier. It completes when all explicit memory accesses before this instruction complete.

__ISB()

void __ISB

(

void

)

Instruction Synchronization Barrier.

Instruction Synchronization Barrier flushes the pipeline in the processor, so that all instructions following the ISB are fetched from cache or memory, after the instruction has been completed.

__LDA()

uint32_t __LDA

(

volatile uint32_t *

ptr

)

Load-Acquire (32 bit)

Executes a LDA instruction for 32 bit values.

Parameters

[in]

ptr

Pointer to data

Returns

value of type uint32_t at (*ptr)

Note

Only available for Armv8-M Architecture.

__LDAB()

uint8_t __LDAB

(

volatile uint8_t *

ptr

)

Load-Acquire (8 bit)

Executes a LDAB instruction for 8 bit value.

Parameters

[in]

ptr

Pointer to data

Returns

value of type uint8_t at (*ptr)

Note

Only available for Armv8-M Architecture.

__LDAEX()

uint32_t __LDAEX

(

volatile uint32_t *

ptr

)

Load-Acquire Exclusive (32 bit)

Executes a LDA exclusive instruction for 32 bit values.

Parameters

[in]

ptr

Pointer to data

Returns

value of type uint32_t at (*ptr)

Note

Only available for Armv8-M Architecture.

__LDAEXB()

uint8_t __LDAEXB

(

volatile uint32_t *

ptr

)

Load-Acquire Exclusive (8 bit)

Executes a LDAB exclusive instruction for 8 bit value.

Parameters

[in]

ptr

Pointer to data

Returns

value of type uint8_t at (*ptr)

Note

Only available for Armv8-M Architecture.

__LDAEXH()

uint16_t __LDAEXH

(

volatile uint32_t *

ptr

)

Load-Acquire Exclusive (16 bit)

Executes a LDAH exclusive instruction for 16 bit values.

Parameters

[in]

ptr

Pointer to data

Returns

value of type uint16_t at (*ptr)

Note

Only available for Armv8-M Architecture.

__LDAH()

uint16_t __LDAH

(

volatile uint16_t *

ptr

)

Load-Acquire (16 bit)

Executes a LDAH instruction for 16 bit values.

Parameters

[in]

ptr

Pointer to data

Returns

value of type uint16_t at (*ptr)

Note

Only available for Armv8-M Architecture.

__LDRBT()

uint8_t __LDRBT

(

uint8_t

ptr

)

LDRT Unprivileged (8 bit)

This function executed an Unprivileged LDRT command for 8 bit value.

Parameters

[in]

ptr

Pointer to data

Returns

value of type uint8_t at (*ptr)

__LDREXB()

uint8_t __LDREXB

(

volatile uint8_t *

addr

)

LDR Exclusive (8 bit) [not for Cortex-M0, Cortex-M0+, or SC000].

This function executed an exclusive LDR command for 8 bit value [not for Cortex-M0, Cortex-M0+, or SC000].

Parameters

[in]

*addr

Pointer to data

Returns

value of type uint8_t at (*addr)

__LDREXH()

uint16_t __LDREXH

(

volatile uint16_t *

addr

)

LDR Exclusive (16 bit) [not for Cortex-M0, Cortex-M0+, or SC000].

This function executed an exclusive LDR command for 16 bit values [not for Cortex-M0, Cortex-M0+, or SC000].

Parameters

[in]

*addr

Pointer to data

Returns

value of type uint16_t at (*addr)

__LDREXW()

uint32_t __LDREXW

(

volatile uint32_t *

addr

)

LDR Exclusive (32 bit) [not for Cortex-M0, Cortex-M0+, or SC000].

This function executed an exclusive LDR command for 32 bit values [not for Cortex-M0, Cortex-M0+, or SC000].

Parameters

[in]

*addr

Pointer to data

Returns

value of type uint32_t at (*addr)

__LDRHT()

uint16_t __LDRHT

(

uint16_t

ptr

)

LDRT Unprivileged (16 bit)

This function executed an Unprivileged LDRT command for 16 bit values.

Parameters

[in]

ptr

Pointer to data

Returns

value of type uint16_t at (*ptr)

__LDRT()

uint32_t __LDRT

(

uint32_t

ptr

)

LDRT Unprivileged (32 bit)

This function executed an Unprivileged LDRT command for 32 bit values.

Parameters

[in]

ptr

Pointer to data

Returns

value of type uint32_t at (*ptr)

__NOP()

void __NOP

(

void

)

No Operation.

This function does nothing. This instruction can be used for code alignment purposes.

__RBIT()

uint32_t __RBIT

(

uint32_t

value

)

Reverse bit order of value.

Parameters

[in]

value

Value to reverse

Returns

Reversed value

__REV()

uint32_t __REV

(

uint32_t

value

)

Reverse byte order (32 bit)

Reverses the byte order in unsigned integer value. For example, 0x12345678 becomes 0x78563412.

Parameters

[in]

value

Value to reverse

Returns

Reversed value

__REV16()

uint32_t __REV16

(

uint32_t

value

)

Reverse byte order (16 bit)

Reverses the byte order within each halfword of a word. For example, 0x12345678 becomes 0x34127856.

Parameters

[in]

value

Value to reverse

Returns

Reversed value

__REVSH()

int16_t __REVSH

(

int16_t

value

)

Reverse byte order (16 bit)

Reverses the byte order in a 16-bit value and returns the signed 16-bit result. For example, 0x0080 becomes 0x8000.

Parameters

[in]

value

Value to reverse

Returns

Reversed value

__ROR()

uint32_t __ROR	(	uint32_t	value,
		uint32_t	shift
	)

Rotate a value right by a number of bits.

This function rotates a value right by a specified number of bits.

Parameters

[in]	value	Value to be shifted right
[in]	shift	Number of bits in the range [1..31]

Returns

Rotated value

__RRX()

uint32_t __RRX

(

uint32_t

value

)

Rotate Right with Extend (32 bit)

This function moves each bit of a bitstring right by one bit. The carry input is shifted in at the left end of the bitstring.

Parameters

[in]

value

Value to rotate

Returns

Rotated value

__SEV()

void __SEV

(

void

)

Send Event.

Send Event is a hint instruction. It causes an event to be signaled to the CPU.

__SSAT()

int32_t __SSAT	(	int32_t	value,
		uint32_t	sat
	)

Signed Saturate.

This function saturates a signed value. The Q bit is set if saturation occurs [not for Cortex-M0, Cortex-M0+, or SC000].

On Armv6-M (Cortex-M0, Cortex-M0+, and SC000) this function is not available as a core instruction instruction and thus __SSAT is implemented in software.

Parameters

[in]	value	Value to be saturated
[in]	sat	Bit position to saturate to [1..32]

Returns

Saturated value

__STL()

void __STL	(	uint32_t	value,
		volatile uint32_t *	ptr
	)

Store-Release (32 bit)

Executes a STL instruction for 32 bit values.

Parameters

[in]	value	Value to store
[in]	ptr	Pointer to location

Note

Only available for Armv8-M Architecture.

__STLB()

void __STLB	(	uint8_t	value,
		volatile uint8_t *	ptr
	)

Store-Release (8 bit)

Executes a STLB instruction for 8 bit values.

Parameters

[in]	value	Value to store
[in]	ptr	Pointer to location

Note

Only available for Armv8-M Architecture.

__STLEX()

uint32_t __STLEX	(	uint32_t	value,
		volatile uint32_t *	ptr
	)

Store-Release Exclusive (32 bit)

Executes a STL exclusive instruction for 32 bit values.

Parameters

[in]	value	Value to store
[in]	ptr	Pointer to location

Returns

0 Function succeeded

1 Function failed

Note

Only available for Armv8-M Architecture.

__STLEXB()

uint32_t __STLEXB	(	uint8_t	value,
		volatile uint8_t *	ptr
	)

Store-Release Exclusive (8 bit)

Executes a STLB exclusive instruction for 8 bit values.

Parameters

[in]	value	Value to store
[in]	ptr	Pointer to location

Returns

0 Function succeeded

1 Function failed

Note

Only available for Armv8-M Architecture.

__STLEXH()

uint32_t __STLEXH	(	uint16_t	value,
		volatile uint16_t *	ptr
	)

Store-Release Exclusive (16 bit)

Executes a STLH exclusive instruction for 16 bit values.

Parameters

[in]	value	Value to store
[in]	ptr	Pointer to location

Returns

0 Function succeeded

1 Function failed

Note

Only available for Armv8-M Architecture.

__STLH()

void __STLH	(	uint16_t	value,
		volatile uint16_t *	ptr
	)

Store-Release (16 bit)

Executes a STLH instruction for 16 bit values.

Parameters

[in]	value	Value to store
[in]	ptr	Pointer to location

Note

Only available for Armv8-M Architecture.

__STRBT()

void __STRBT	(	uint8_t	value,
		uint8_t	ptr
	)

STRT Unprivileged (8 bit)

This function executed an Unprivileged STRT command for 8 bit values.

Parameters

[in]	value	Value to store
[in]	ptr	Pointer to location

__STREXB()

uint32_t __STREXB	(	uint8_t	value,
		volatile uint8_t *	addr
	)

STR Exclusive (8 bit) [not for Cortex-M0, Cortex-M0+, or SC000].

This function executed an exclusive STR command for 8 bit values [not for Cortex-M0, Cortex-M0+, or SC000].

Parameters

[in]	value	Value to store
[in]	*addr	Pointer to location

Returns

0 Function succeeded

1 Function failed

__STREXH()

uint32_t __STREXH	(	uint16_t	value,
		volatile uint16_t *	addr
	)

STR Exclusive (16 bit) [not for Cortex-M0, Cortex-M0+, or SC000].

This function executed an exclusive STR command for 16 bit values [not for Cortex-M0, Cortex-M0+, or SC000].

Parameters

[in]	value	Value to store
[in]	*addr	Pointer to location

Returns

0 Function succeeded

1 Function failed

__STREXW()

uint32_t __STREXW	(	uint32_t	value,
		volatile uint32_t *	addr
	)

STR Exclusive (32 bit) [not for Cortex-M0, Cortex-M0+, or SC000].

This function executed an exclusive STR command for 32 bit values [not for Cortex-M0, Cortex-M0+, or SC000].

Parameters

[in]	value	Value to store
[in]	*addr	Pointer to location

Returns

0 Function succeeded

1 Function failed

__STRHT()

void __STRHT	(	uint16_t	value,
		uint16_t	ptr
	)

STRT Unprivileged (16 bit)

This function executed an Unprivileged STRT command for 16 bit values.

Parameters

[in]	value	Value to store
[in]	ptr	Pointer to location

__STRT()

void __STRT	(	uint32_t	value,
		uint32_t	ptr
	)

STRT Unprivileged (32 bit)

This function executed an Unprivileged STRT command for 32 bit values.

Parameters

[in]	value	Value to store
[in]	ptr	Pointer to location

__USAT()

uint32_t __USAT	(	int32_t	value,
		uint32_t	sat
	)

Unsigned Saturate.

This function saturates an unsigned value. The Q bit is set if saturation occurs [not for Cortex-M0, Cortex-M0+, or SC000].

On Armv6-M (Cortex-M0, Cortex-M0+, and SC000) this function is not available as a core instruction instruction and thus __USAT is implemented in software.

Parameters

[in]	value	Value to be saturated
[in]	sat	Bit position to saturate to [0..31]

Returns

Saturated value

__WFE()

void __WFE

(

void

)

Wait For Event.

Wait For Event is a hint instruction that permits the processor to enter a low-power state until an events occurs:

• If the event register is 0, then WFE suspends execution until one of the following events occurs:
  • An exception, unless masked by the exception mask registers or the current priority level.
  • An exception enters the Pending state, if SEVONPEND in the 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, then WFE clears it to 0 and returns immediately.

__WFI()

void __WFI

(

void

)

Wait For Interrupt.

WFI is a hint instruction that suspends execution until one of the following events occurs:

• A non-masked interrupt occurs and is taken.
• An interrupt masked by PRIMASK becomes pending.
• A Debug Entry request.