Propeller Manual

2: Spin Language Reference – WORD
Propeller Manual v1.1 · Page 229
Word Data Declaration (Syntax 2)
In
DAT blocks, syntax 2 of WORD is used to declare word-aligned, and/or word-sized data that is
compiled as constant values in main memory.
DAT blocks allow this declaration to have an
optional symbol preceding it, which can be used for later reference. See
DAT
T
, page 99. For
example:
DAT
MyData word 640, $AAAA, 5_500 'Word-aligned/word-sized data
MyList byte word $FF99, word 1_000 'Byte-aligned/word-sized data
The above example declares two data symbols, MyData and MyList. MyData points to the start
of word-aligned and word-sized data in main memory.
MyData’s values, in main memory, are
640, $AAAA and 5,500, respectively.
MyList uses a special DAT block syntax of WORD that
creates a byte-aligned but word-sized set of data in main memory.
MyList’s values, in main
memory, are $FF99 and 1,000, respectively. When accessed a byte at a time,
MyList contains
$99, $FF, 232 and 3 since the data is stored in little-endian format.
This data is compiled into the object and resulting application as part of the executable code
section and may be accessed using the read/write form, syntax 3, of
WORD (see below). For
more information about using
WORD in this way, refer to the DAT section’s Declaring
Data(Syntax 1) on page 100 and keep in mind that
WORD is used for the Size field in that
description.
Data items may be repeated by using the optional Count field. For example:
DAT
MyData word 640, $AAAA[4], 5_500
The above example declares a word-aligned, word-sized data table, called MyData, consisting
of the following six values: 640, $AAAA, $AAAA, $AAAA, $AAAA, 5500. There were
four occurrences of $AAAA due to the
[4] in the declaration immediately after it.
Reading/Writing Words of Main Memory (Syntax 3)
In
PUB and PRI blocks, syntax 3 of WORD is used to read or write word-sized values of main
memory. This is done by writing expressions that refer to main memory using the form:
word[BaseAddress][Offset]. Here’s an example.
PUB MemTest | Temp
Temp := word[@MyData][1] 'Read word value
word[@MyList][0] := Temp + $0123 'Write word value