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Text File | 1991-08-16 | 10.9 KB | 369 lines

asm(1.1), an AmigaDOS compatible 68010 assembler Deviations from AmigaDOS manual Copyright (c) 1986 Douglas J Leavitt Jr. 3005 OFW #2, Venice CA, 90291 Usenet: sdcrdcf!ism780c!dougl Suggested contribution: $25-$50 Intro This paper describes the functions and capabilities available with the asm(1.1) macro assembler. The asm assembler is designed to be a 68010 macro assembler that is compatible with the assembler described in the AmigaDOS Manual, from Commodore-Amiga Inc., and Bantam Computer Books. Because this assembler tries to be as compatible as possible with the AmigaDOS assembler, only the deviations from that manual will be discussed here. At some later point in time, a totally new manual may be written. The asm(1.1) assembler was designed with three principles in mind. 1. An assembler that is available to everyone. 2. An assembler capable of assembling any currently available assembly language written for the Amiga. 3. An assembler with more power than is available in the standard AmigaDOS macro assembler. The first goal of has been met by making this assembler a shareware product. By making this assembler shareware product it is hoped that it's availability will become widespread, providing a general increase in Amiga software, and ultimately providing a better Amiga environment for all people. This assembler is intended as the first part of an entire C compilation system that will eventually be provided as a shareware system for all Amiga users. This paper is organized in the same sections as the AmigaDOS assembler manual chapter. Deviations from The AmigaDOS Manual Chapter 3 3.1 Introduction to the 68000/68010 Microchip This assembler is capable of compiling the new instructions that are available with the 68010. This means that three new registers and three new instructions are available. These are: 1. sfc, dfc, vbr registers, and 2. movec, movec.l 3. moves.b, moves.w, moves.l 4. rtd instructions This assembler is also capable of determining whether a branch may be generated in the 8 or 16 bit form automatically. The way that this is accomplished, is by using a jcc instruction. For example, if the assembler encounters a jne instruction, it will automatically determine if it can generate a bne.s or if must generate a bne instruction. 3.2 Calling asm(1.1) For the most part asm(1.1) tries to be as flexible as possible whenever possible. The assembler does not require a specific command line argument order. The current legal arguments are: asm [options] assembly_file [options] options: ? - Display command line format -q - Silent mode (copyright notice not shown) -l file - Generate listing file -h file - Include header file -o file - Output file name -i incl - Add include list to searching -v file - Gererate errors to verification file The -c flag does not currently exist with this release of the assembler. These options are expected to appear in a later release. 3.3.2.3 This assembler is capable of accepting either upper case or lower case opcodes. Whenever an instruction is encountered without a size specifier, word sized opcodes are assumed. Whenever the opcode field contains a local label that has been defined to be an absolute constant, asm(1.1) will generate the equivalent of a dc.w whose value is the value of the label. Opcodes may not currently start in the first character of an assembly line. Asm(1.1) is not capable of determining whether an opcode starting in the first character position is a label or an opcode. 3.3.2.4 The restriction of not allowing whitespace characters, blanks and tabs, between operands has been removed. 3.3.2.5 If a comment immediately follows a zero operand instruction and the comment starts with a word rather than a comment delimiter such as ';', the word will be taken as a symbol. This is not currently seen as a problem because the comment character ';' may always be placed immediately after a zero operand instruction. 3.4.1 All expression calculations are in signed 32 bit calculations which are then truncated if necessary. 3.4.3 A symbol is a string of up to 64 characters. The special symbol '.' has the value of the current program counter. This symbol is equivalent to '*'. The symbol '*' does exist in this assembler. The '.' symbol has been provided because of it's significance in many other assembly languages. 3.4.4 When a hex constant is being parsed, the characters 'a'-'f' as well as 'A'-'F' are legal values for the numbers 10-15. Ascii literals are normally contained in single quotes "'". Ascii strings are legal operands in many assembler directives. An ascii string is very similar to a C type string. An ascii string is a sequence of ascii characters contained in double quotes. The following sequences exist in strings: 1. \r - carraige return 2. \n - newline 3. \t - tab character 4. \f - formfeed 5. \b - backspace 6. \\ - backslash 7. \07 - \ followed by 1-3 octal characters generates the desired 8 bit character sequence. Double quoted strings will work with any operand that requires a string. Single quoted strings will work for those directives that document it as such. These directives, ifc/ifnc, accept both singly or doubly quoted strings and treat them the same. 3.5 Absolute short addresses are denoted by appending a '.w' suffix to the address. The '.l' suffix may also be appended to a long absolute address. The REG directive does not currently exist in this assembler, however it is possible to specify by name a list of registers that will be saved in a movem instruction other than a simple immediate value constant. The following operand form is legal for the movem instruction: register_name[|register_name[|register_name...]] An example: movem.l d7|d6|d5|a4|a3,-(sp) The asm(1.1) assembler will generate the correct mask for all legal addressing modes, predecrement included. 3.6 The Asm(1.1) release of the assembler has been updated so that all "I", "A", and "M" variants now exist. 3.7 As many directives as possible have been supported in this assembler. This section describes the current limitations and additions to the existing assembler directives. The following directives are not currently supported in this version of the assembler. They are accepted, however they are ignored. 1. offset 2. rorg 3. reg The following directives are supported in this assembler, but do not exist in the standard Amiga macro assembler. 1. text, code, data, bss 2. global, globl 3. comm 4. even, align 5. ascii, asciz 6. else Assembler Control Directives SECTION The section directive currently supports only 3 sections. These sections are one each of CODE, DATA, and BSS. Each of these sections may share a common section name, or they may be unnamed, which is the default. TEXT, CODE These directives change the current section to become the code section. Neither directive takes an operand, and the section name is assumed to the current section name. DATA This directive change the current section to become the data section. This directive does not take an operand, and the section name is assumed to the current section name. BSS This directive change the current section to become the bss section. This directive does not take an operand, and the section name is assumed to the current section name. Data Definition Directives COMM This directive has the following form: COMM symbol,N This directive places the given symbol into the BSS section with a size of N. N is a constant expression that defines the size of the symbol in byte units. ASCII This directive has the following form: [<label>] ASCII string This directive generates N bytes of data. The generated data is a set of ascii bytes whose values are represented in the given string. A NUL ('\0') termination character is NOT generated with this directive. N is the number of characters that exist in the string. ASCIZ This directive has the following form: [<label>] ASCIZ string This directive generates N+1 bytes of data. The generated data is a set of ascii bytes whose values are represented in the given string. A NUL ('\0') termination character is generated with this directive. N is the number of characters that exist in the string. Listing Control Directives LLEN This directive will accept and check the legal values, however the changed value is ignored. PLEN This directive now has a default of 66 lines per page. TTL The program title may be up to 64 characters long in this directive. Conditional Assembly Directives ELSE This directive changes the true/false condition of the currently active if directive. This directive does not have arguments. Else directives may be nested just like other ifxx directives. When else directives are nested, the current else pertains to the most recent open if directive. Alignment Directives EVEN This directive aligns the current section on an even boundary by generating 0 or 1 zero bytes of data. ALIGN This directive has the following form: ALIGN N This directive aligns the current section on a mod N boundary. 0 to N-1 bytes of zero data will be generated to properly change the alignment as requested. External Symbols GLOBAL, GLOBL These directives have the following form: GLOBAL symbol1[,symbol2[,symbol3...]] or GLOBL symbol1[,symbol2[,symbol3...]] These directives take one or more labels, and generate each label as an externally defined symbol. These directives perform the same functionality as XREF and XDEF, but have provided for compatibility with other assemblers. Other Differences The following is a list of other known differences between this assembler, and the AmigaDOS macro assembler document. 1. An assembly line may be up to 128 characters in length. 2. There may be up to 8 different levels of nested includes. 3. Macro expansion allows for up to 24 separate macro arguments. 4. Up to 8 different include paths may exist in each assembly. 5. Conditional assemblies may be nested 16 deep. 6. Macro expansions may be nested 16 deep. 7. There is currently a maximum limit on the number of ifd/ifnd directives. That limit is currently a total of 512 ifd and ifnd directives. Acknowledgements Amiga, AmigaDOS, and Alink Are trademarks of Commodore-Amiga, Inc. The AmigaDOS Manual is printed by Bantam computer Book, and is Copyright (c) 1986 Commodore Capital, Inc. 68000/68010/68020/68030/68881/Motorola Are trademarks of Motorola Microsystems, Inc. Unix Is a trademark of AT&T.