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CROSS ASSEMBLER->Conditional Assembly

Conditional assembly allows code to be included or excluded from the assembly depending on particular conditions.  The IFcc and ENDC directives serve to define the statements to be conditional assembled.  If the operand to the particular IFcc directive satisfies the required condition, the statements up to the following ENDC will be assembled, otherwise they will be skipped.  The required condition depends on the particular IFcc directive as follows:
    

Directive	Condition

IFEQ	<Expression> =  0
IFNE	<Expression> <> 0
IFGE	<Expression> >= 0
IFGT	<Expression> >  0
IFLE	<Expression> <= 0
IFLT	<Expression> <  0
IFC	<Character string 1> = <Character string 2>
IFNC	<Character string 1> <> <Character string 2>

Conditional assembly directives can be nested.

The UNA/NOUNA directives (described in section  ) control the listing of unassembled statements. Note that the unassembled statements, if they are listed, are not formatted.  If the UNA directive is not used only the ENDC command is listed (again unformatted).  

The CLIST/NOCLIST directives (described in section  ) control the listing of the IFcc and ENDC statements themselves.

An example which shows the use of conditional assembly, and also of the FAIL directive follows:

PAGE  001  ifexample.asm              Sat Nov 13 22:33:02 1993
          conxampl          ** Conditionals **

   1                            nam    conxampl
   2                            ttl    ** Conditionals **
   3                            list
   4 0040                       pagewidth 64
   5                            fields 7,7,11
   6                            una
   7                            clist
   8
   9 0001                flag   defl   1
  10 0001                flag2  defl   1
  11
  12 5F00                       org    $5F00
  13
  14 0001                       ifeq   flag
  15                             ld a,(albert)
  16                             ld (fred),a
  17                             endc
  18
  19 0000                       ifeq   flag-1     if flag=1
                                                  assemble to
                                                  endc
  20 5F00 3A 09 5F              ld     a,(albert)
  21 5F03 32 0B 5F              ld     (morris),a
  22
  23 5F06                                         * Nested
  24 5F06                                         * conditional
  25
  26 FFFE                       ifle   flag2-3    if flag2<=3,
                                                  assemble
  27 5F06 32 0A 5F              ld     (fred),a
  28 0000                       ifeq   flag2-1    if flag2=1,
                                                  assemble

ifexample.asm: **** WARNING at line 29      Fail directive encountered
  29                            fail              trap flag2=1
  30                            endc
  31                            endc
  32                            endc
  33
  34 5F09                albert defs   1
  35 5F0A                fred   defs   1
  36 5F0B                morris defs   1
  37                            end
Assembly complete
Total bytes generated: 12
0 errors
1 warnings