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The code comes from the RGBDS source and documentation zip files found on this website: http://www.otakunozoku.com/1999/08/01/rednex-gameboy-development-system/ The same website reports: "Best of all, it’s free! That’s right! Free! The executables are free to use, either for personal hobby use, or full blown commercial productions — I know of at least a dozen commercial games you can purchase that are written with RGBDS — and the source code is free to modify. "The only thing I ask is that you do not charge for either distributing the executables or source code, and any derivative works you give credit to the original authors of the tools. That means you have to say “Thanks” to the original authors SurfSmurf and Otaku." Signed-off-by: Vegard Nossum <vegard.nossum@gmail.com>
101 lines
2.4 KiB
HTML
101 lines
2.4 KiB
HTML
<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 3.2//EN">
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<HTML>
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<HEAD>
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<TITLE>xAsm Gameboy</TITLE>
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</HEAD>
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<BODY BGCOLOR="#692764" TEXT="#F5A0D8" LINK="#8AAEE6" VLINK="#2B9DA4" ALINK="#95F0DA">
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<I><H2>Gameboy
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</H2></I>
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<HR>
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<P>The full GB-Z80 instruction-set is implemented with a few modifications to the original Zilog syntax. This is due
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to a Bison problem but in my opinion the syntax is better than the original one.<BR>
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<H4><BR>
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Instructions</H4>
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<PRE> ADC
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ADD
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AND
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BIT
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CALL
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CCF
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CP
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CPL
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DAA
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DEC
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DI
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EI
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EX
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HALT
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INC
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JP
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JR
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LD
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LDD
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LDI
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LDH/LDIO (see note below)
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NOP
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OR
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POP
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PUSH
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RES
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RET
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RETI
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RL
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RLA
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RLC
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RLCA
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RR
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RRA
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RRC
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RRCA
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RST
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SBC
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SCF
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SET
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SLA
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SRA
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SRL
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STOP
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SUB
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SWAP
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XOR</PRE>
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<P>Note that you can use both
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<PRE> OR A,B
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OR B</PRE>
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<H4><BR>Addressingmodes</H4>
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<P>Indirect addressing has been changed to [ ] instead of ( ):<BR>
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<PRE> A
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B
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C
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D
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E
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H
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L
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AF
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BC
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DE
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HL
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SP
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[BC]
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[DE]
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[HL]
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[HL-]/[HLI]
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[HL+]/[HLD]
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[SP]
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n8 (8 bit expression)
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n16 (16 bit expression)
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n3 (3 bit CONSTANT expression)
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[n16]/[$FF00+n8]
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[$FF00+C]/[C]</PRE>
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<P>The assembler will intelligently decide between <B>[n16]</B> and <B>[$FF00+n8]</B> in the LD instruction. Note however that if you use any <A HREF="symbols.htm">constant symbols</A> in the expression they had better be defined before the instruction or your symbol-table may become mangled. Also worth noting is that it will only ever select the short $FF00 mode when you use constant symbols. NOT if you use symbols defined in a <A HREF="section.htm">HRAM section</A>. As this defies the whole point of implementing the HRAM sectiontype I've added the LDIO mnemonic. It works like the LD instruction but it will ALWAYS generate the $FF00+ form and it will also automatically logically AND the expression with $FF if it is relocatable. Which is what you want. Trust me ;)<BR>
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<BR>
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<H4>Conditioncodes</H4>
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<PRE> C
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NC
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Z
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NZ</PRE>
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<BR><HR>
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<FONT SIZE="-1"><I><P ALIGN=RIGHT>Last updated 20 July 1997 by <A HREF="mailto:surfsmurf@matilde.demon.co.uk">Carsten Sorensen</A></P></I></FONT>
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