C166: Using the _atomic_ Function

Information in this article applies to:

• C166 All Versions

QUESTION

How can I use the _atomic_ function in my programs to create atomic sections?

ANSWER

The _atomic_ and _endatomic_ library routines specify the start and end of an atomic code section. This section of code must be 4 instructions or less. Use atomic sections to protect program code from hardware interrupts. Instructions in an atomic section are executed as an atom and cannot be interrupted.

For example:

#include

bit testbit;

void function (int flag)
{
_atomic_ (0);
if (flag == 1)
  testbit = 1;
_endatomic_ ();
}

Generates the following code:

0000 D120          ATOMIC    #03H
0002 4881          CMP       R8,#01H
0004 3D01          JMPR      cc_NZ,?C0001
0006 0F00     R    BSET      testbit
0008         ?C0001:
0008 CB00          RET

which uses the ATOMIC instruction to protect the specified code.

MORE INFORMATION

• Refer to _atomic_ in the C166 User's Guide.
• Refer to _endatomic_ in the C166 User's Guide.

SEE ALSO

• C166: Error 185 (Atomic #5 Out of Range)
• C166: EXTS Problems Using the _ATOMIC_ Function

Last Reviewed: Thursday, February 25, 2021