Filter
Top Products
7
CHAPTER 2 MEMORY SPACE
2.2 Memory Space and Addressing
In addressing by the F
2
MC-8FX CPU, the applicable addressing mode related to memory
access may change according to the address.
Therefore, the use of the proper addressing mode increases the code efficiency of
instructions.
■ Memory Space and Addressing
The F
2
MC-8FX CPU has the following addressing modes related to memory access. ([ ] indicates one
byte):
• Direct addressing: Specify the lower 8 bits of the address using the operand. The accesses of operand
address 00
H
to 7F
H
are always 0000
H
to 007F
H
. The accesses of operand address
80
H
to FF
H
are mapped to 0080
H
to 047F
H
by setting of direct bank pointer (DP).
[Structure] [← OP code →] [← lower 8 bits →] ([← if operand available →]
• Extended addressing:Specify all 16 bits using the operand.
[Structure] [← OP code →] [← upper 8 bits →] [← lower 8 bits →]
• Bit direct addressing:Specify the lower 8 bits of the address using the operand. The accesses of operand
address 00
H
to 7F
H
are always 0000
H
to 007F
H
. The accesses of operand address
80
H
to FF
H
are mapped to 0080
H
to 047F
H
by setting of direct bank pointer (DP).
The bit positions are included in the OP code.
[Structure] [← OP code: bit →] [← lower 8 bits →]
• Indexed addressing: Add the 8 bits of the operand to the index register (IX) together with the sign and
use the result as the address.
[Structure] [← OP code →] [← 8 offset bits →] ([← if operand available →])
• Pointer addressing: Use the contents of the extra pointer (EP) directly as the address.
[Structure] [← OP code →]
• General-purpose register addressing: Specify the general-purpose registers. The register numbers are
included in the OP code.
[Structure] [← OP code: register →]
• Immediate addressing:Use one byte following the OP code as data.
[Structure] [← OP code →] [← Immediate data →]
• Vector addressing: Read the data from a table corresponding to the table number. The table numbers
are included in the OP code.
[Structure] [← OP code: table →]
• Relative addressing: Calculate the address relatively to the contents of the current PC. This addressing
mode is used during the execution of the relative jump and bit check instructions.
[Structure] [← OP code: table →] [← 8 bit relative value →]
Figure 2.2-1 shows the memory space accessible by each addressing mode.