56 lines
1.3 KiB
Groff
56 lines
1.3 KiB
Groff
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\" $Header$
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.TH 6800_AS 1
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.ad
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.SH NAME
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6800_as \- assembler for Motorola 6800
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.SH SYNOPSIS
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/usr/em/lib/6800_as [options] argument ...
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.SH DESCRIPTION
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This assembler is made with the general framework
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described in \fIuni_ass\fP(6).
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.SH SYNTAX
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.IP registers
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The 6800 has two accumulator registers, A and B. An instruction that refers
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to accumulator A, has an "a" as last character. In the same way a "b" means
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that the instruction uses B as accumulator.
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.IP "addressing modes"
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.nf
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.ta 8 16 24 32 40 48
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syntax meaning (name)
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#expr with cpx, ldx, lds a 2-byte value,
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otherwise a 1-byte value (immediate)
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<expr 1-byte address. Not allowed with:
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asl, asr, clr, com, dec, inc, lsl, lsr,
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neg, rol, ror, tst (base page direct)
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expr 2-byte address (extended direct)
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expr, x 1-byte expr + contents of x
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yields address (indexed)
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.fi
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.SH "SEE ALSO"
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uni_ass(6),
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ack(1),
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.br
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A. Osborne, 6800 programming for logic design,
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Adam Osborne and Associates Inc., 1977
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.SH EXAMPLE
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An example of Motorola 6800 assembly code.
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.sp 2
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.nf
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.ta 8 16 32 40 48 56 64
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.data
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val: 0
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.text
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ldx <val
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com val, x
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bhs someplace ! branch on carry clear
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sta <val
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adda #18 ! add 18 to accumulator A
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.fi
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.SH BUGS
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You have to specify whether an address fits in one byte
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with the token `<'. It should be done automatically.
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