Zilog Z8F0130 - Manual (Page 342)

Using the Macro Assembler UM013037-1212
318
Zilog Developer Studio II – Z8 Encore!
User Manual
•
Structured Assembly Inputs – see page 319
•
Structured Assembly Processing – see page 323

The assembler directives associated with structured assembly are summarized in the fol-
lowing table.
The assembler directives shown in the table are known collectively as structured assembly
test directives and are always used together to form a homogeneous structured assembly
block. The assembler supports one decision structure (
.$IF ) and two looping structures
( .$WHILE and .$REPEAT ).
The assembler supports a decision structure with the . $IF , .$ELSEIF , .$ELSE , and
.$ENDIF directives. These directives generate code to test one or more execution-time
conditions and execute a block of statements based on the result of the tests.
For example, in the following decision structure:
.$if (r0 == #0)

ld r0,r1

.$else

ld r0,r2

.$endif
the assembler generates the following code:
000000 A6E000A 2.$if (r0 == #0)

000003 EB 05

000005 E4E1E0A 3ld r0,r1

000008 8B 03A 4.$else

00000A E4E2E0A 5ld r0,r2

00000DA 6.$endif
The assembler supports two types of looping structures with the .$WHILE , .$WEND , and
.$REPEAT , .$UNTIL directive pairs. The .$WHILE directive generates code to test an
execution-time condition and executes a block of statements while the condition is true.
Since the test is performed before executing the block, the block might not be executed.
Table 54. Assembler Directives for Structured Assembly
Assembler Directive Description
.$IF, .$REPEAT, .$WHILE Structured assembly test primary
$ELSEIF Structured assembly test alternate
.$ELSE Structured assembly test default
.$BREAK, .$CONTINUE Structured assembly test control
.$ENDIF, .$UNTIL, .$WEND Structured assembly test end