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Z80 assembler written in Common Lisp
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SherpaPierpa/z80
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Written 2004 by Ingvar Mattsson <[email protected]> This is a Z80 assembler. Input files are named <filename>.l80. This code is in the public domain. Input file format is (essentially) a lispified Z80 assembler notation, mostly driven by macros. At the moment, the error checking is kind-of vague, so should any input data be in too bad a shape, it will indeterministically do an assortment of things. There are some "virtual instructions" available. - ORG sets the "where will this instruction end up" parameter. - DB deposits one or more bytes at "the current position" - DSTR deposits the (ASCII) bytes (and only the ASCII bytes) corresponding to a given string. Some 8-bit characters may end up actually working, but taht hasn't been designed for. - LABEL creates a label (for data load or jumping to). The label name can be used instead of a word immediate anywhere and can be used as a jump target for JR. - JMP is the generic jump instruction, it will turn into JP or JR as necessary and will use minimal space. In general, where there are two or more ways of expressing an instruction in Z80 machine code, this assembler will generate the shortest one. This assembler understands (in f (c)) and will generate the right code. THE ASSEMBLE FUNCTION The ASSEMBLE function takes an infile designator as its required argument. It also accepts two keyword arguments, :FILETYPE and :OUTPUT-EXTRAS, these are passed on to the ASSEMBLER-OUTPUT generic function. The first (:FILETYPE) determines what method will be called and teh second is a method-specific set of extra data (for SNA, that is the contents of the header or, rather, the contents of anything non-zero in the header). SYNTAX The general syntax is: (mmn target source) For instructions that have conditionals (CALL, RET, JP, JR), the syntax is: (mmn <(flags flag)> destination) In most places where a 16-bit immediate can be placed, you can use a label reference. Indirection is done by placing the register/immediate in parentheses. Thus: hl Contents of HL (hl) Contents of memory with the address in HL (+ ix d) Contents of memory with the address of IX+d (indirect indexed) INTERNALS All "user-visible" instructions are implemented as CL macros, expanding into a call to ASM-FUN. This function does some checking of arguments (extracting conditionals and the like) and then builds an ASMINSTR object with the instruction, source, target and possibly flag specification. This object also contains the range of "address for first byte" (this is usually a range of 1 bye, so lowest possible and highest possible address is the same, but in code that uses the virtual JMP instruction, this may vary). This function also takes care to associate labels with instructions. When the whole program has been loaded and parsed, the assembler will styart by sorting code from lowest possible start address to highest possible start address. It will then go throuhg and convert JMPs to JR or JP as needed, until it has converted all of them. It has *not* been proven that this process terminates, but... After that is done, it will create a 64 K element array and get the actual machine code for the symbolic instruction and write it into this array. All bytes that have been left untouched will have the value -1 instead of a value in the range 0-255. Once this is done, it will open an output file and call the function ASSEMBLER-OUTPUT with the array, the output file stream and the output format specifier (so the relevant output method can be chosen).
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