W65C816S Datasheet, PDF (52/62 Pages) List of Unclassifed Manufacturers – Microprocessor

The Western Design Center, Inc.
W65C816S Data Sheet
7 RECOMMENDED W65C816S ASSEMBLER SYNTAX STANDARDS
7.1 Directives
Assembler directives are those parts of the assembly language source program which give directions to the
assembler; this includes the definition of data area and constants within a program. This standard excludes any
definitions of assembler directives.
7.2 Comments
An assembler should provide a way to use any line of the source program as a comment. The recommended
way of doing this is to treat any blank line, or any line that starts with a semi-colon or an asterisk as a comment.
Other special characters may be used as well.
7.3 The Source Line
Any line which causes the generation of a single W65C816S machine language instruction should be divided
into four fields: a label field, the operation code, the operand, the comment field.
7.3.1 The Label Field
The label field begins in column one of the line. A label must start with an alphabetic character,
and may be followed by zero or more alphanumeric characters. An assembler may define an upper
limit on the number of characters that can be in a label, so long as that upper limit is greater than or
equal to six characters. An assembler may limit the alphabetic characters to upper-case characters
if desired. If lower-case characters are allowed, they should be treated as identical to their
upper-case equivalents. Other characters may be allowed in the label, so long as their use does not
conflict with the coding of operand fields.
7.3.2 The Operation Code Field
The operation code shall consist of a three character sequence (mnemonic) from Table 7-1. It
shall start no sooner than column 2 of the line, or one space after the label if a label is coded.
7.3.2.1
Many of the operation codes in Table 6-1 have duplicate mnemonics; when two or
more machine language instruction has the same mnemonic, the assembler resolves the difference
based on the operand.
7.3.2.2
If an assembler allows lower-case letters in labels, it must also allow lower-case
letters in the mnemonic. When lower-case letters are used in the mnemonic, they shall be treated as
equivalent to the upper-case counterpart. Thus, the mnemonics LDA, lda and LdA must all be
recognized, and are equivalent.
7.3.2.3
In addition to the mnemonics shown in Table 7-1, an assembler may provide the
alternate mnemonics shown in Table 7-1.
The Western Design Center
W65C816S
52