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H8/300 Dependent Features

See the following documentation for the Hitachi H8/300 architecture’s features and options for the assembler.

Options for H8/300

Syntax for H8/300

Special Characters for H8/300

Register Names for H8/300

Addressing Modes for H8/300

Floating Point for H8/300

Machine Directives for H8/300

Opcodes for H8/300

Options for H8/300

as has no additional command-line options for the Hitachi H8/300 family.

Syntax for H8/300

The following documentation refers to the syntax for the Hitachi H8/300.

Special Characters for H8/300

; 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.

Register Names for 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.

Addressing Modes for H8/300

as understands the following addressing modes for the H8/300.

rn
Register direct

@rn
Register indirect

@(d, rn)

@(d:16, rn)

@(d:24, rn)
Register indirect: 16-bit or 24-bit displacement d from register n. (24-bit displacements are only meaningful on the H8/300H.)

@rn+
Register indirect with post-increment.

@-rn
Register indirect with pre-decrement.

@aa

@aa:8

@aa:16

@aa:24
Absolute address aa. (The address size :24 only makes sense on the H8/300H.)

#xx

#xx:8

#xx:16

#xx:32
Immediate data xx. You may specify the ‘:8’, ‘:16’, or ‘:32’ for clarity, if you wish; but as neither requires this nor uses it—the data size required is taken from context.

@@aa

@@aa:8
Memory indirect. You may specify the ‘:8’ for clarity, if you wish; but as neither requires this nor uses it.

Floating Point for H8/300

The H8/300 family has no hardware floating point, but the .float directive generates IEEE floating-point numbers for compatibility with other development tools.

Machine Directives for H8/300

as has only one machine-dependent directive for the H8/300:

.h8300h
Recognize and emit additional instructions for the H8/300H variant, and also make .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.

Opcodes for H8/300

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 vari-ants 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 instance, since r0 refers to a 16-bit register, note the distinctions in the following examples.

mov r0,@foo

mov w r0,@foo

If you use the size suffixes, as issues a warning when the suffix and the register size do not match.