Fujitsu MB90460 Series, Hardware Manual, Page: 74 / 739

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CHAPTER 3 CPU
3.8 General-purpose Registers
The general-purpose registers are a memory block allocated in RAM at 000180
H
to
00037F
H
as banks, each of which consists of eight 16-bit segments.
The general-purpose registers can be used as general-purpose 8-bit registers (byte
registers R0 to R7), 16-bit registers (word registers RW0 to RW7) or 32-bit registers
(long-word registers RL0 to RL7).
General-purpose registers can access RAM with a short instruction at high speed.
Since general-purpose registers are blocked into register banks, protection of register
contents and division into function units can readily be performed. When a general-
purpose register is used as a long-word register, it can be used as a linear pointer that
directly accesses the entire space.
■
Configuration of a General-purpose Register
All general-purpose registers exist in RAM at 000180
H
to 00037F
H
and are configured as 32 banks. The
register bank pointer (RP) specifies the bank that is to be used for a general-purpose register. The RP
points to the bank currently being used.
The RP determines the first address of each bank with the following formula:
Address of first general-purpose register = 000180
H
+ RP x 10
H
Figure 3.8-1 shows the location and
configuration of the general-purpose register banks in the memory space.
Figure 3.8-1 Location and Configuration of the General-purpose Register Banks in the Memory Space
Note:
The register bank pointer (RP) is initialized to 00
H
after a reset.
Built-in RAM
Register bank 31
Register bank 30
Register bank 21
Register bank 20
Register bank 19
Register bank 2
Register bank 1
Register bank 0
Conversion formula [000180
H
+ RP x 10
H
]
Byte address
Byte address
R0 to R7:
RW0 to RW7:
RL0 to RL3:
MSB:
LSB: Byte registers
Word registers
Long-word registers
Most Significant Bit
Least Significant Bit