as
has no additional command-line options for the Hitachi
H8/300 family.
`;' is the line comment character.
`$' can be used instead of a newline to separate statements. Therefore you may not use `$' in symbol names on the H8/300.
You can use predefined symbols of the form `rnh' and `rnl' to refer to the H8/300 registers as sixteen 8-bit general-purpose registers. n is a digit from `0' to `7'); for instance, both `r0h' and `r7l' are valid register names.
You can also use the eight predefined symbols `rn' to refer to the H8/300 registers as 16-bit registers (you must use this form for addressing).
On the H8/300H, you can also use the eight predefined symbols `ern' (`er0' ... `er7') to refer to the 32-bit general purpose registers.
The two control registers are called pc
(program counter; a
16-bit register, except on the H8/300H where it is 24 bits) and
ccr
(condition code register; an 8-bit register). r7
is
used as the stack pointer, and can also be called sp
.
as understands the following addressing modes for the H8/300:
rn
@rn
@(d, rn)
@(d:16, rn)
@(d:24, rn)
@rn+
@-rn
@
aa
@
aa:8
@
aa:16
@
aa:24
aa
. (The address size `:24' only makes
sense on the H8/300H.)
#xx
#xx:8
#xx:16
#xx:32
as
neither
requires this nor uses it--the data size required is taken from
context.
@
@
aa
@
@
aa:8
as
neither requires this nor uses it.
The H8/300 family has no hardware floating point, but the .float
directive generates IEEE floating-point numbers for compatibility
with other development tools.
as
has only one machine-dependent directive for the
H8/300:
.h8300h
.int
emit 32-bit numbers rather than the usual (16-bit)
for the H8/300 family.
On the H8/300 family (including the H8/300H) `.word' directives generate 16-bit numbers.
For detailed information on the H8/300 machine instruction set, see H8/300 Series Programming Manual (Hitachi ADE--602--025). For information specific to the H8/300H, see H8/300H Series Programming Manual (Hitachi).
as
implements all the standard H8/300 opcodes. No additional
pseudo-instructions are needed on this family.
Four H8/300 instructions (add
, cmp
, mov
,
sub
) are defined with variants using the suffixes `.b',
`.w', and `.l' to specify the size of a memory operand.
as
supports these suffixes, but does not require them;
since one of the operands is always a register, as
can
deduce the correct size.
For example, since r0
refers to a 16-bit register,
mov r0,@foo is equivalent to mov.w r0,@foo
If you use the size suffixes, as
issues a warning when
the suffix and the register size do not match.
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