.\" $Header$
.TH 6805_AS 6 "$Revision$"
.ad
.SH NAME
6805_as \- assembler for Motorola 6805
.SH SYNOPSIS
~em/lib.bin/6805/as [options] argument ...
.SH DESCRIPTION
This assembler is made with the general framework
described in \fIuni_ass\fP(6). It is an assembler generating relocatable
object code in \fIack.out\fP(5) format.
.SH SYNTAX
.IP registers
The 6805 has an accumulator register A and an index register X. An
instruction (from the read-modify-write group) that references the
A-register has an "a" suffixed to the mnemonic. In a similar way
the X-register, apart from indexing operations, is addressed with
an "x" suffix, i.e. "lsra" and "negx".
.IP "addressing modes"
The assembler automatically selects the shortest opcode if
appropriate and possible. Thus "sub 10" will use the direct
addressing mode whereas "neg 0,x" will use indexed (no offset) mode.
There are sick constructions where the assembler can't find out
the shortest form in time. In those cases the longest form is used.
.br
Branches are handled in much the same way. If a branch is out of
range it is replaced by a reversed condition branch, followed by
a jump, automatically.
.sp
.nf
.ta 8n 16n 24n 32n 40n 48n
syntax		meaning (name)

#expr		a one byte value (immediate)
<expr		1-byte zero page address. Allowed in  
		the register/memory and read-modify-
		write instruction groups. (direct)
>expr		2-byte address. Allowed in the register
		memory group. (extended)
expr		1-byte address if appropriate, 2-byte 
		in other cases. (auto-direct/extended)
,x		indexed with zero offset. (indexed)
<expr,x		indexed with 8 bit offset. (indexed-1)
>expr,x		indexed with 16 bit offset. (indexed-2)
expr,x		indexed with the shortest possible off-
		set. (auto indexed)
bit,expr	bit number and direct address. 
		(bit set/clear)
bit,expr,tag	bit number, direct address and branch 
		tag. Automatically changed to reversed 
		condition branch and jump if appropri-
		ate. (bit test and branch)
tag		branch tag. Converted to reversed con-
		dition branch and jump if appropriate. 
		(branch)
.fi
.IP "PSEUDO INSTRUCTIONS"
 
 .cmos		assemble cmos version instructions.
.SH "SEE ALSO"
uni_ass(6),
ack(1),
ack.out(5)
.br
M6805 HMOS, M146805 CMOS family, Motorola, 
Prentice-Hall, Inc., 1983, (ISBN 0-13-541375-3).
.SH AUTHOR
Written by Gijs Mos.
Not a member of the ACK group.
.SH BUGS
The assembler has not been well tested.