as has no additional command-line options for the Hitachi
`;' 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).
used as the stack pointer, and can also be called
as understands the following addressing modes for the H8/300:
aa. (The address size `:24' only makes sense on the H8/300H.)
asneither requires this nor uses it--the data size required is taken from context.
asneither requires this nor uses it.
The H8/300 family has no hardware floating point, but the
directive generates IEEE floating-point numbers for compatibility
with other development tools.
as has only one machine-dependent directive for the
.intemit 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 (
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,
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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