ref: f81bcc722a9a4d335068e1f122f51b8b188ace40
dir: /doc/asm/trg_gb.htm/
<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 3.2//EN">
<HTML>
<HEAD>
<TITLE>xAsm Gameboy</TITLE>
</HEAD>
<BODY BGCOLOR="#692764" TEXT="#F5A0D8" LINK="#8AAEE6" VLINK="#2B9DA4" ALINK="#95F0DA">
<I><H2>Gameboy
</H2></I>
<HR>
<P>The full GB-Z80 instruction-set is implemented with a few modifications to the original Zilog syntax. This is due
to a Bison problem but in my opinion the syntax is better than the original one.<BR>
<H4><BR>
Instructions</H4>
<PRE> ADC
ADD
AND
BIT
CALL
CCF
CP
CPL
DAA
DEC
DI
EI
EX
HALT
INC
JP
JR
LD
LDD
LDI
LDH/LDIO (see note below)
NOP
OR
POP
PUSH
RES
RET
RETI
RL
RLA
RLC
RLCA
RR
RRA
RRC
RRCA
RST
SBC
SCF
SET
SLA
SRA
SRL
STOP
SUB
SWAP
XOR</PRE>
<P>Note that you can use both
<PRE> OR A,B
OR B</PRE>
<H4><BR>Addressingmodes</H4>
<P>Indirect addressing has been changed to [ ] instead of ( ):<BR>
<PRE> A
B
C
D
E
H
L
AF
BC
DE
HL
SP
[BC]
[DE]
[HL]
[HL-]/[HLI]
[HL+]/[HLD]
[SP]
n8 (8 bit expression)
n16 (16 bit expression)
n3 (3 bit CONSTANT expression)
[n16]/[$FF00+n8]
[$FF00+C]/[C]</PRE>
<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>
<BR>
<H4>Conditioncodes</H4>
<PRE> C
NC
Z
NZ</PRE>
<BR><HR>
<FONT SIZE="-1"><I><P ALIGN=RIGHT>Last updated 20 July 1997 by <A HREF="mailto:[email protected]">Carsten Sorensen</A></P></I></FONT>