Hitachi H8/500 Series - Instructions; Basic Instruction Formats; Data Formats on the Stack

Table 3-6 Data Formats on the Stack
3.4 Instructions
3.4.1 Basic Instruction Formats
There are two basic CPU instruction formats: the general format and the special format.
General format: This format consists of an effective address (EA) field, an effective address
extension field, and an operation code (OP) field. The effective address is placed before the
operation code because this results in faster execution of the instruction.
• Effective address field: One byte containing information used to calculate the effective
address of an operand.
• Effective address extension: Zero to two bytes containing a displacement value, immediate
data, or an absolute address. The size of the effective address
extension is specified in the effective address field.
• Operation code: Defines the operation to be carried out on the operand located at
the address calculated from the effective address information.
Some instructions (DADD, DSUB, MOVFPE, MOVTPE) have
an extended format in which the operand code is preceded by a
one-byte prefix code.
Data Type Data Format
Byte data
on stack
Word data
on stack
MSB
LSB
Upper 8 bits
Lower 8 bits
Even address
Odd address
Even address
Odd address MSB LSB
Don’t-care
Effective address field Effective address extension Operation code
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