Atmel SAM4S Xplained Pro Starter Kit Atmel ATSAM4S-XSTK ATSAM4S-XSTK Data Sheet

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SAM4S [DATASHEET]

11100E–ATARM–24-Jul-13

    CMPEQ   R0, #0              ; Did this succeed?

    BNE     try                 ; No – try again

    ....                        ; Yes – we have the lock

Clear Exclusive. 

Syntax

CLREX{cond}

where:

cond

Operation

Use CLREX to make the next STREX, STREXB, or STREXH instruction write 1 to its destination register and fail to
perform the store. It is useful in exception handler code to force the failure of the store exclusive if the exception occurs
between a load exclusive instruction and the matching store exclusive instruction in a synchronization operation.

See 

 for more information.

Condition Flags

These instructions do not change the flags.

Examples

CLREX