RAS - Mobile Robot Assembler

Mobile Robot Assembler (RAS) is an assembler for mobile robots and, in general, any system based on Motorola 68HC11 microcontrollers, multiplatform, expandable and free.

In the current version it recognizes the complete instruction set of the MC68HC11 microcontroller family and some directives (basically, ORG, EQU and memory allocation) that are commented in the documentation.

If you are not interested in other alternatives for programming these micros neither the features and motivations of the Mobile Robot Assembler (RAS), you can directly reach the Download area.

Motorola distributes the as11, a widely used and freeware assembler for its MC68HC11 on which Randy Sargent carried out a few modifications. Its features are relatively limited, for example, macros can not be created and all the program code must go in the same source file. This causes that it is uncomfortable to work with it. However, it even offers good results for programs of certain complexity.

Another possibility within the assembler's world is to use the GNU Assembler. It is a really good product with the GNU guarantee but it could be complicated for the novice mainly in the beginning. It has everything what can be asked as assembler, a good documentation and, mainly, its open philosophy.

Also it is possible to use the C/C++ as base language, very near to the assembler language on the other hand. In this scope, the most used and portable tool is the GNU C/C++ compiler. Like the GNU Assembler, above commented, the GNU C/C++ compiler could be somewhat complicated in the beginning.

More information on other languages and development systems for this microcontroller can be readed the 68HC11 FAQ.

The main idea at the time of creating a new assembler considering the antecedents that we have mentioned is to define a development environment that can be provided by new instructions from other already existing ones. The new meta-instructions will generate the code corresponding to frequently used functions in mobile robot programs, for example, activating the analog/digital converters, reading sensor ports, movement commands for actuators, etc.

The final goal is a high level language for mobile robots formed by a library of meta-instructions included and maked in the language.

In the most basic level we have a language for programming our control system. On this level some frequently used functions in this kind of systems will be located. In higher levels, basic robot behaviors, like the well known follow-line behavior or even complete mobile robot control architectures, can be defined.

To use an assembler as base language is due to that we can take advantage of the limited resources on the robot control system. Generally they are systems with a few of memory bytes and low processing speed. The more powerful and optimized it is our meta-instructions library, the less code in assembler we will have to create.

• Version 0.1.2 (16-Apr-2001)
• New
• RMB directive for reserve memory.
• ZMB directive for reserve memory, each byte is assigned the initial value of zero.
• Fixed Bugs
• Fixed minor bugs during the code generation phase.
• Version 0.1.1 (12-Mar-2001)
• New
• RPM distribution.
• Install and uninstall options in the Makefile and scripts for GNU/Linux.
• Fixed Bugs
• The BRSET and BRCLR instructions have a correct behaviour when the program starts at an address different to $0000.
• Version 0.1.0 (06-Mar-2001)
• New
• New -v option for showing some assembling results (length of the generated code, area of memory used for the program code, etc.).
• New FCC directive for strings of characters. The string delimiter is the symbol ". To include a " into the string, simply put it twice (example, "the ""white"" house").
• Modifications
• Now the FCB and FBD directives are as11-compatible, so, several values (symbolic and numeric) separated by commas are allowed in each directive and it is not mandatory the label field.
• Some grammar functions and data structures have been modified to improve the general performance.
• Fixed Bugs
• Now, if a symbol duplicated error is detected and the symbol is in two different source files (using the include directive), the file name where is the second occurrence and the line number is displayed by the error message. Previously, the displayed file name was the included file and the line number was the main file; obviously, there was not that symbol in the line number displayed.
• Version 0.0.3 (27-Feb-2001)
• New
• New include directive that includes a source file from another one. The directive uses the file name to be included as argument (for example, include file.asm) and a macro-expansion is carried out. Symbols and labels are treated as globals and a redefinition will produce a compiling error. Ten levels deep are allowed.
• Fixed Bugs
• Now, if the ORG directive is not used in the beginning of the program, the default start address is $0000.
• For DOS/Windows version, the end of line can be defined by both CR and LF characters.
• Version 0.0.2 (12-Feb-2001)
• New
• New FCB and FBD directives for memory allocation (variables), 1 and 2 bytes, respectively.
• New manual page (man).
• Improvements
• The labels can be ended by the `:' character in the label field but it does not consider in its use in operands.
• When the offset in the indexed addresing is not specified (for example CLR ,X) it is assumed that the offset is 0.
• ASCII constants are allowed putting the character ' before the constant value (for example, LDAA 'B loads the ASCII value of the character B in the accumulator A). If ' is followed by a string, only the first character is considered.
• Mnemonics are case-insensitives but labels and symbols are case-sensitives.
• It is verified the value of the operand is within the allowed rank [-128 .. +127] in branch instructions.
• Fixed Bugs
• Now the program returns 0 if there are no errors and 1 otherwise.
• If an ORG directive overlapped the code addresses there was an incorrect code generation.
• Mnemonics names can be used as labels, the type of symbol (mnemonic or label is obtained by the context (for example, BRA stop).
• Version 0.0.1 (09-Feb-2001)
• Complete instruction set, compatible with the Motorola assembler.
• EQU y ORG directives.
• Addressing modes: inherent, immediate, direct, extended, indexed and relative.
• Detection of syntactic and semantic errors (verification of operand sizes).
• Debug options (symbol table and intermediate code).

• It does not detect errors in source files similar to "$#10", so wrong formed inmediate addressing with hexadecimal operands (the correct expresion would be "#$10"). The programmer can detect this kind of errors because the shell command returns a "$" symbol.

• Source listings with instruction cycles.
• The first meta-instruction.

• GNU/Linux
• ras-0.1.2-1.i386.rpm (binaries rpm, 26 Kb)
• ras-0.1.2.tar.gz (binaries, 31 Kb)
• ras-0.1.2.src.tar.gz (sources, 22 Kb)
• DOS/Windows
• ras-0.1.2.zip (binaries, 318 Kb)
• GNU General Public License (English ASCII, English HTML, Español HTML)

Thanks to Juan González for betatesting, porting to DOS/Windows and preparing the RPM distribution. Also thanks to Cecilio Ruiz for betatesting and for their suggestions.

This program is free software; you can redistribute it and/or modify it under the terms of the GNU General Public License as published by the Free Software Foundation; either version 2 of the License, or (at your option) any later version.

This program is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License for more details (available on line in the Download section of this page).

The current version is BETA. During the testing we have verified that the code generated for every instruction and addressing mode is identical to the generated by the as11 assembler. The test programs are distributed the source package. They do not have any logical sense and DO NOT HAVE TO BE LOADED in the microcontroller.