Zilog ZUSBOPTS Uživatelský manuál stáhnout pdf (Strana 270)

100

101

Directives UM017105-0511

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Zilog Developer Studio II – ZNEO™

User Manual

Once applied to label tname, the individual structure elements are applied to tname to pro-

duce the desired offsets using tname as the structure base. For example, the label

tname.name_2 is created and assigned the value tname + stag.name_2. If there are

any alignment requirements with the structure, the

.TAG directive attaches the required

alignment to the label. The optional count on the

.TAG directive is meaningful only inside

a structure definition and implies an array of the

.TAG structure.

Keeping the space allocation separate allows you to place the .TAG declarations that assign

structure to a label in the header file in a similar fashion to the

.STRUCT and XREF direc-

tives. You can then include the header file in multiple source files wherever the label is

used. Make sure to perform the space allocation for the label in only one source file.

Examples of the

.TAG directive are as follows:

DATE .STRUCT

MONTH DS 1

DAY DS 1

YEAR DS 2

DSIZE .ENDSTRUCT DATE

NAMELEN EQU 30

EMPLOYEE .STRUCT

NAME DS NAMELEN

SOCIAL DS 10

START .TAG DATE

SALARY DS 1

ESIZE .ENDSTRUCT EMPLOYEE

NEWYEARS .TAG DATE

NEWYEARS DS DSIZE

The .TAG directive in the last example above creates the symbols NEWYEARS.MONTH,

NEWYEARS.DAY, and NEWYEARS.YEAR. The space for NEWYEARS is allocated by the DS

directive.

.UNION Directive

The .UNION directive is similar to the .STRUCT directive, except that the offset is reset to

zero on each label. A

.UNION directive cannot have an offset or parent union. The key-

word to terminate a

.UNION definition is .ENDSTRUCT.

Note:

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