Assembler Structured Control-flow Quick Reference

The full tutorial on how it works

The source code for the IAR MSP430 version of the macros

When you #include the above header file, the following control-flow structures become available in assembly language.

Conditional branches

 
 <test>
 _IF cc
  ... 
 _ENDIF
 
 
 <test>
 _IF cc
  ...
 _ELSE 
  ...
 _ENDIF
 
 
Where cc is one of Z, NZ, EQ, NE, C, NC, HS, LO, N, NN, L, GE or NEVER.
 
 

Uncounted loops

 
 _REPEAT
  ...
 _FOREVER ; Infinite
 
 
 _REPEAT
  ...
  <test> ; Post-tested
 _UNTIL cc
 
 
 _DO
  <test> ; Pre-tested
 _WHILE cc
  ...
 _ENDW
 
 
 _DO
  ...
  <test> ; Mid tested
 _WHILE cc
  ...
 _ENDW

Any loop may have additional _WHILE s to exit it, but each additional one must be balanced by an _ENDIF (or _ELSE ... _ENDIF) after the end of the loop. Examples:

_DO ... _WHILE cc1 ... _WHILE cc2 ... _ENDW ... _ENDIF

_REPEAT ... _WHILE cc1 ... _UNTIL cc2 ... _ELSE ... _ENDIF

_REPEAT ... _WHILE cc1 ... _WHILE cc2 ... _FOREVER ... _ENDIF ... _ENDIF

Counted loops

Typical use:

; Word counter, single decrement, 0 means 65536 times

_FOR #10,R8

... ; Will be done 10 times.

_NEXT_DEC R8 ; Must use same destination as matching _FOR

; Word counter, double decrement, 0 means 32768 times

_FOR #10,R9 ; Must be even

... ; Will be done 5 times.

_NEXT_DECD R9 ; Minus 2 each time, so R9 takes on only even values.

; Byte counter, single decrement, 0 means 256 times

_FOR_B #10,R8

... ; Will be done 10 times.

_NEXT_DEC_B R8 ; Must use same destination as matching _FOR_B

; Byte counter, double decrement, 0 means 128 times

_FOR_B #10,R9 ; Must be even

... ; Will be done 5 times.

_NEXT_DECD_B R9 ; Minus 2 each time, so R9 takes on only even values.

Short-circuit-AND

_COND

<test1>

_AND_IF cc1

<test2>

_AND_IF cc2

<test3>

_AND_IF cc3

...

_ENDIFS ; Note the plural

Short-circuit-AND with ELSE

_COND

<test1>

_AND_IF cc1

<test2>

_AND_IF cc2

<test3>

_AND_IF cc3

...

_ELSES ; Note the plural

...

_ENDIF ; Note the singular. Use the plural _ENDIFS only if there is no _ELSES clause

Short-circuit OR

_COND

<test1>

_OR_ELSE cc1

<test2>

_OR_ELSE cc2

<test3>

_OR_IFS cc3 ; Note the plural

...

_ENDIF

Short-circuit OR with ELSE

_COND

<test1>

_OR_ELSE cc1

<test2>

_OR_ELSE cc2

<test3>

_OR_IFS cc3 ; Note the plural

...

_ELSE

...

_ENDIF

Short-circuit AND/OR

_COND

<test1>

_AND_IF cc1

_COND ; Note the second _COND

<test2>

_OR_ELSE cc2

<test3>

_OR_IFS cc3 ; Note the plural

...

_ENDIFS ; Note the plural

Short-circuit AND/OR with ELSE

_COND

<test1>

_AND_IF cc1

_COND ; Note the second _COND

<test2>

_OR_ELSE cc2

<test3>

_OR_IFS cc3 ; Note the plural

...

_ELSES ; Note the plural

...

_ENDIF ; Note the singular. Use the plural _ENDIFS only if there is no _ELSES clause

Comparison of short-circuit structures (plurals shown red and green)

_COND <test1> _AND_IF cc1 <test2> _AND_IF cc2 <test3> _AND_IF  cc3 ... _ENDIFS
_COND <test1> _AND_IF cc1 <test2> _AND_IF cc2 <test3> _AND_IF  cc3 ...  _ELSES ... _ENDIF
_COND <test1> _OR_ELSE cc1 <test2> _OR_ELSE cc2 <test3>  _OR_IFS cc3 ... _ENDIF
_COND <test1> _OR_ELSE cc1 <test2> _OR_ELSE cc2 <test3> _OR_IFS cc3 ...  _ELSE ... _ENDIF

_COND <test1> _AND_IF cc1 _COND <test2> _OR_ELSE cc2 <test3> _OR_IFS cc3 ... _ENDIFS

_COND <test1> _AND_IF cc1 _COND <test2> _OR_ELSE cc2 <test3> _OR_IFS cc3 ...  _ELSES ... _ENDIF

Else-If chain

_COND

<test1>

_IF cc1

...

_ELSE

<test2>

_IF cc2

...

_ELSE

<test3>

_IF cc3

...

_ELSE

...

_ENDIFS ; Note the plural

Case statement

Typical use:

_CASE

_OF_EQ #1,R8 ; Uses a word comparison

...

_ENDOF

_OF_EQ_B #’A’,R8 ; Uses a byte comparison

...

_ENDOF

<test1> ; A general test

_OF cc1

...

_ENDOF

... ; The default case

_ENDCASE

Structure balance check (at end of program or subroutine)

_CS_CHECK

-- Dave Keenan, 2018-Jan-10 (last updated 2018-Nov-14)