-*[ NES ASM v2.51 ]*- --------------- Usage ----- NESASM [-options] [-? (for help)] infile[.ASM] The assembler accepts only one input file 'infile' that will be assembled into ROM file (.NES extension) directly useable by an emulator. A listing file can also be generated (.LST extension) if the LIST directive is encountered in the input file. Here's a description of the different options: Option Description ------ ----------- -s -S Show segment usage. If one of those options is specified the assembler will display information on the ROM bank usage. Use '-s' to show basic information and '-S' to show more detailed information. -l # Control output of the listing file: 0 - disable completely the listing file even if the LIST directive is used in the input file 1 - minimun level; code produced by DB, DW and DEFCHR will not be dumped 2 - normal level; only code produced by DEFCHR will not be dumped 3 - maximun level; all the code is dumped in the listing file The default level is level 2. -m Force macros expansion in the listing file, even if the MLIST directive is not seen in the input file. -raw Control the header generation. By default the assembler always adds an header to the ROM file; unless '-raw' is specified, in this case no ROM header is generated. Include path ------------ By default the assembler looks in the current directory when loading an include file, but when it doesn't find the file it then uses the environment variable 'NES_INCLUDE' to get a list of include paths. Ideally, you will want to set this variable in your 'AUTOEXEC.BAT' file, and have it point to the 'NES' directory of MagicKit. ex: set NES_INCLUDE=c:\magickit\nes Symbols ------- Two types of symbol are supported, global symbols and local symbols. Local symbols are preceded by a dot '.' and are valid only between two global symbols. A symbol can be followed by a colon ':' but this is not necessary. Expressions ----------- The assembler supports very complex expressions. You can use as many level of parenthesis as you want and spaces between operators and numbers are possible. Numbers can be written in three bases : hexadecimal ($7F), binary (%0101) and decimal (48). Character values are also supported ('A'). All the usual operators are present : +, -, *, /, %, ^, &, |, ~, <<, >> As well as the comparison operators : =, !=, !, <, >, <=, >= For the priority, the same rules as C apply. You can also use predefined or user-defined functions in an expression. Predefined functions -------------------- HIGH() - Returns the high byte of a value. LOW() - Returns the low byte. BANK() - Returns the bank index of a symbol. If no symbol, or more than one, are given, the function will return an error. PAGE() - Returns the page index of a label. See above for errors. SIZEOF() - Returns the size of a data element. User-defined functions ---------------------- User-defined functions are declared with the .FUNC directive, for example: SCR_ADDR .func (\1) + ((\2) << 5) Up to nine arguments, \1 to \9, can be used. To call a function simply enclose arguments within parenthesis and separate them with a comma: stw #SCR_ADDR(10,4)+$2000,<$20 User-defined functions can be very useful, one often needs to use the same calculation again and again in expressions. Defining a function will save you a lot of work, and reduce typo errors. :) Note that function calls can be nested, you can call one function from another without any problem, however, recursive calls will produce an error. Macros ------ While functions are very useful to replace common expressions by just a function call, macros are used to replace common groups of instructions by a single line of code. You start a macro definition with: label .macro Or you can also place the label after the '.macro' keyword, like this: .macro label After follow the body of the macro, which is terminated by the '.endm' directive. As an example let's define a 'neg' macro to negate the accumulator. neg .macro eor #$FF inc A .endm Macros can also have parameters. In the macro body, you refer to a parameter by using the backslash character ('\') followed by a digit. Nine parameters can be used, \1 to \9. Here's another example: add .macro ; add a value to register A clc ; (handle carry flag) adc \1+1 .endm Other 'special' parameters can be used, here's a list of all the possible parameter you can use inside a macro: Parameter Description --------- ----------- \1 - \9 Input parameter - up to nine can be used in a macro call \# Number of input parameters \?1 - \?9 Returns 'type' of input parameter: ARG_NONE (= 0) = No argument ARG_REG (= 1) = register -> A, X, Y ARG_IMMEDIATE (= 2) = Immediate data type -> #xx ARG_ABSOLUTE (= 3) = Abosulte addressing -> label, $xxxx ARG_INDIRECT (= 4) = Indirect addressing -> [label] ARG_STRING (= 5) = String argument -> "..." ARG_LABEL (= 6) = Label argument -> label \@ Special parameter that returns a different number for each macro; can be used to define local symbols inside macros: abs .macro lda \1 bpl .x\@ eor #$FF inc A sta \1 .x\@: .endm Directives ---------- LIST - Enable the listing file generation. You can later stop temporarily the output with the NOLIST directive and restart it again with LIST. NOLIST - Stop the listing output. MLIST - Allow macro expansion in the listing file. NOMLIST - Stop expanding macros in the listing file. This directive won't have any effect if you use the '-m' command line option. OPT - ... EQU - Assign a value to a symbol. The character '=' has the same function too. BANK - Select a 8KB ROM bank (0-127) and reset the location counter to the latest known position in this bank. ORG - Set the location of the program counter. The thirteen lower bits of the address inform the assembler about the offset in the ROM bank and the third upper bits represent the page index. DB - Store one or more data bytes at the current location. DW - Store data words. BYTE - Same as DB. WORD - Same as DW. DS - Reserve space at the current location. This space will be filled with zeroes if this directive is used in the CODE or DATA group. RSSET - Set the internal counter of the RS directive to a specified value. RS - Assign a value to a symbol; a bit like EQU but here the value assigned is taken from an internal counter, and after the assignation this counter is increased by the amount specified in the RS directive. This is a very handy way of defining structure member offsets, here's a small example: ; C: ; -- ; struct { ; short p_x; ; short p_y; ; byte p_color; ; } pixel; ; ; ASM: ; ---- .rsset $0 ; set the initial value of RS counter P_X .rs 2 P_Y .rs 2 P_COLOR .rs 1 You can later use these symbols as offsets in a 'pixel' struct: ldy #P_COLOR lda [pixel_ptr],Y MACRO - Start a macro definition. ENDM - End a macro definition. PROC - ... ENDP - ... PROCGROUP - ... ENDPROCGROUP - ... INCBIN - Include a binary file at the current location. If the file is bigger than a ROM bank, as many successive banks as necessary will be used. INCLUDE - Include a source file at the current location. Up to 7 levels are possible. INCCHR - Extract a part of a PCX file and convert it into NES 4-color 8x8 graphic characters. Three syntaxes are possible : INCCHR "pic.pcx" Without any additional parameters, the command convert the whole PCX file. INCCHR "pic.pcx",32,4 Tell the assembler to convert only 4 rows of 32 characters (a character size is 8x8). INCCHR "pic.pcx",48,16,32,4 Same as above but start extracting characters from coordinate 48,16 (in pixels). DEFCHR - Define a character tile (8x8 pixels). The directive takes 8 arguments (stored as 32-bit values of 8 nybbles each), one argument for each row of pixel data. This directive takes also care to reorganize the pixel data to the NES required bit format. Note that only color indexes 0 to 3 can be used, as the NES tiles are only 4-color. An error will be generated if you try to use more colors. zero: .defchr $00111110,\ $01000011,\ $01000101,\ $01001001,\ $01010001,\ $01100001,\ $00111110,\ $00000000 ZP - Select the Zero-Page section ($0000-$00FF). BSS - Select the RAM section ($0200-$07FF). CODE - Select the program code section. DATA - Select the program data section. Note: In ZP and BSS sections you can only allocate storage, ---- you can *not* store initial values. IF - Conditional assembly directive. This directive will evaluate the supplied expression and then turn conditional assembly on or off depending on the result. If the result is null conditional assembly is turned off, and on if the result is non null. IFDEF IFNDEF - These directives allow conditional assembly depending on whether a label is defined or not. ELSE - Toggle conditional assembly on to off, or vice verca. ENDIF - Terminate the current level of conditional assembly. Report an error if the number of IF's and ENDIF's doesn't match. FAIL - When the assembler encounters this directive, it aborts the compilation. Can be used within a macro for argument error detection. INESPRG - Specifies the number of 16k prg banks. INESCHR - Specifies the number of 8k chr banks. INESMAP - Specifies the NES mapper used. INESMIR - Specifies VRAM mirroring of the banks. Refer to iNES header document (neshdr20.txt). --