Differences between propasm and the Propeller Tool Assembler

Deviations

The Parallax assembler syntax is not specified by a formal grammar, or completely documented in any one place. Thus, propasm may deviate from the Parallax syntax in subtle ways. I encourage any users that discover such deviations to report them to me immediately.

Limitations

These are features in the Parallax assembler that are currently missing from propasm. All are planned for future addition, except where noted.

• propasm only assembles image files; no open-source program can actually load them onto the Propeller.
• propasm does not yet support inline arithmetic/logic expressions for constants and operands.
• propasm does not support the funky Parallax additions to the US-ASCII character set; it only supports the international Unicode standard. This will not be fixed.

An up-to-date list of bugs is available on the Issue Tracker on our Google Code page.

Extensions

• propasm supports UTF-8 encoding for all source files, and allows any Unicode letter character in identifiers. (It does not yet recognize double-width digits or letters, as used for Roman inclusions in Chinese documents; this will be fixed.)
• propasm supports additional directives, prefixed with a dot to distinguish them from the Parallax directives:
  • .align allows you to specify an alignment for a point in the source file (using byte, word, or long). The assembler will pad as needed.
  • .include pulls in another source file at that point in the program.

Bugfixes

These are deliberate deviations from the behavior of Parallax's assembler, to fix aspects that I consider bugs. (Most of these issues are described in more detail in Phil Pilgrim's Propeller Tricks and Traps document.)

• propasm will not allow out-of-range constant values, as in the following:

  data   byte #$A5A5A5A5
  

  The Parallax assembler allows these, and silently truncates to the low-order n bits. This is a syntax error in propasm.
• propasm will not allow a read-only register to be used in an operation's D field, as in the following:

     test INA, #1 wz
  

  Such an instruction will fail in interesting ways at runtime. If you really must specify a read-only register in D, you may explicitly specify its numeric address — e.g. $1F2 for INA.
• propasm will behave in a sane fashion if a RES directive is immediately followed by a data directive, such as LONG — that is, it will reserve the specified number of longwords before the data is placed. The Parallax assembler silently ignores these RES directives. (propasm is likely to treat this as a syntax error in an upcoming version.)
• propasm will allow the CALL pseudo-operation to be used with a local label pair.