Filter
Top Products
31
CHAPTER 3 CPU
3.2.2 Register Bank Pointer (RP)
The register bank pointer (RP) is the upper 8 bits of the program status register (PS).
The register bank pointer indicates the general-purpose register bank address being
used, and the address is converted to the actual address in general-purpose register
addressing.
■ Configuration of the Register Bank Pointer (RP)
Figure 3.2-4 shows the configuration of the register bank pointer.
Figure 3.2-4 Configuration of Register Bank Pointer
The register bank pointer indicates the address of the register bank being used. Figure 3.2-5 shows the rule
of conversion from the register bank pointer bits to the actual address.
Figure 3.2-5 Rule of Conversion from the RP Bits to the Actual Address
The register bank pointer specifies a memory block (register bank) used as a general-purpose register in the
RAM area. There are 32 register banks. Setting a value (from 0 to 31) in the upper five bits of the register
bank pointer specifies a register bank. One register bank contains eight 8-bit general-purpose registers that
are selected with the lower 3 bits of an operation code.
The register bank pointer allows a range of 0100
H
to 01FF
H
(maximum) to be used as the general-purpose
register area. However, some models restrict the usable range when only internal RAM is used. The initial
value of the register bank pointer specified after the reset operation is undefined.
Note:
Be sure to set up the register bank pointer (RP) before using general-purpose registers.
The register bank pointer is part of the program status register (PS), and thus is not allowed to access
only the register bank pointer.
RP CCR
bit15 bit14 bit13 bit12 bit11 bit10
bit9 bit8 bit7
bit6 bit5 bit4 bit3 bit2 bit1 bit0
PS R4 R3 R2 R1 R0
-- -
H I IL1 IL0 N Z V C
XXXXXXXX
B
RP initial value
X: Undefined
R4 R3 R2 R1 R0 b2 b1 b0
A15 A14 A13 A12 A11 A10 A9 A8 A7 A6 A5 A4 A3 A2 A1 A0
"0"
RP upper bits
Lower bits of operation code
Address
generated
"0" "0" "0" "0" "0"
"0"
"1"