5.5 Directives that Perform Alignment and Reserve Space

These directives align the section program counter (SPC) or reserve space in a section:

The .align directive aligns the SPC at a 1-byte to 32K-byte boundary. This ensures that the code following the directive begins on the byte value that you specify. If the SPC is already aligned at the selected boundary, it is not incremented. Operands for the .align directive must equal a power of 2 between 2⁰ and 2¹⁵, inclusive.

Figure 5-3 demonstrates the .align directive. Using the following assembled code:

     1 00000000 40000000           .field 2,3
     2 00000000 4000000B           .field 11, 21
     3                             .align 2
     4 00000004 45                 .string "Errcnt"
       00000005 72
       00000006 72
       00000007 63
       00000008 6E
       00000009 74
     5                             .align
     6 0000000c 04                 .byte 4

Figure 5-3 The .align Directive

The .bes and .space directives reserve a specified number of bytes in the current section. The assembler fills these reserved byres with 0s. You can reserve a specified number of words by multiplying the number of bytes by 4.
- When you use a label with .space, it points to the first byte that contains reserved bits.
- When you use a label with .bes, it points to the last byte that contains reserved bits.

Figure 5-4 shows how the .space and .bes directives work for the following assembled code:

     1
     2 00000000 00000100          .word 100h, 200h
       00000004 00000200
     3 00000008           Res_1:  .space 17
     4 0000001c 0000000F          .word 15
     5 00000033           Res_2:  .bes 20
     6 00000034 BA                .byte 0BAh

Res_1 points to the first byte in the space reserved by .space. Res_2 points to the last byte in the space reserved by .bes.

Figure 5-4 The .space and .bes Directives