.\" $Header$
.TH 6800_AS 1
.ad
.SH NAME
6800_as \- assembler for Motorola 6800
.SH SYNOPSIS
/usr/em/lib/6800_as [options] argument ...
.SH DESCRIPTION
This assembler is made with the general framework
described in \fIuni_ass\fP(6).
.SH SYNTAX
.IP registers
The 6800 has two accumulator registers, A and B. An instruction that refers
to accumulator A, has an "a" as last character. In the same way a "b" means
that the instruction uses B as accumulator.
.IP "addressing modes"
.nf
.ta 8 16 24 32 40 48
syntax		meaning (name)

#expr		with cpx, ldx, lds a 2-byte value,
		otherwise a 1-byte value (immediate)

<expr		1-byte address.  Not allowed with:
		asl, asr, clr, com, dec, inc, lsl, lsr,
		neg, rol, ror, tst (base page direct)

expr		2-byte address (extended direct)

expr, x		1-byte expr + contents of x
		yields address (indexed)
.fi
.SH "SEE ALSO"
uni_ass(6),
ack(1),
.br
A. Osborne, 6800 programming for logic design,
Adam Osborne and Associates Inc., 1977
.SH EXAMPLE
An example of Motorola 6800 assembly code.
.sp 2
.nf
.ta 8 16 32 40 48 56 64
	.data
	val:	0
	.text
		ldx	<val
		com	val, x
		bhs	someplace	! branch on carry clear
		sta	<val
		adda	#18		! add 18 to accumulator A
.fi
.SH BUGS
You have to specify whether an address fits in one byte
with the token `<'. It should be done automatically.