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CHAPTER 2 CPU
MB90560 series
2.7
2.7.5 Register bank pointer (PS: RP)
Dedicated Registers
The register bank pointer (RP) is a register that indicates the first address of the
general-purpose register bank currently being used. The RP is used for real address
conversion when general-purpose register addressing is used.
I
Register bank pointer (RP)
Figure 2.7-10 shows the configuration of the register bank pointer (RP) register.
Figure 2.7-10 Configuration of the register bank pointer (RP)
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General-purpose register area and register bank pointer
The register bank pointer points to the relationship between the general-purpose register of the
F
2
MC-16LX and the address in internal RAM where the general-purpose register exists. Figure
2.7-11 shows the conversion rules used for the relationship between the contents of the RP and
the real address.
Figure 2.7-11 Conversion rules for physical address of general-purpose register area
Since the RP takes a value from 00
H
to 1F
H
, the first address of the register bank can be set
in the range from 000180
H
to 00037F
H
.
Although an assembler instruction can use an 8-bit immediate value transfer instruction for
transfer to the RP, in actuality only the lower 5 bits of the data are used.
The initial value of the RP register after a reset is 00
H
.
RP initial value
B4
B0
B1
B2
B3
Conversion formula
When RP = 10
H
Register bank 31
Register bank 16
Register bank 0