Figure 3.2.2A Structure Of Register Bank Pointer; Figure 3.2.2B Rule For Conversion Of Actual Addresses Of General-Purpose Register Area - Fujitsu F2MC-8L MB89620 Series Hardware Manual

3.2 Dedicated Registers
3.2.2 Register Bank Pointer (RP)
The register bank pointer (RP) located in the upper 8 bits of the program status (PS)
indicates the address of the general-purpose register bank currently in use. The RP is
converted to form the actual address in general-purpose register addressing.
n Structure of Register Bank Pointer (RP)
Figure 3.2.2a shows the structure of the register bank pointer.
Bit 15 Bit 14 Bit 13 Bit 12 Bit 11Bit 10 Bit 9 Bit 8 Bit 7 Bit 6 Bit 5 Bit 4 Bit 3 Bit 2 Bit 1 Bit 0
PS
X: Indeterminate
The register bank pointer indicates the address of the register bank currently in use. Figure
3.2.2b shows the relationship between the pointer contents and the actual address is based on
the conversion rule.
Generated addresses
The register bank pointer points to the memory block (register bank) in the RAM area that is
used for general-purpose registers. A total of 32 register banks are available. A register bank is
specified by setting a value between 0 and 31 in the upper 5 bits of the register bank pointer.
Each register bank contains eight 8-bit general-purpose registers. Registers are specified by the
lower 3 bits of the operation codes.
Using the register bank pointer, the addresses 0100
purpose register area. However, the available area is limited on some products if internal RAM
only is used. The initial value after a reset is indeterminate.
Check: The register bank pointer is part of the program status (PS) and cannot be accessed
40
CHAPTER 3 CPU
RP
R4 R3 R2 R1 R0 —

Figure 3.2.2a Structure of Register Bank Pointer

"0" "0"
A15 A14 A13 A12 A10 A11 A9
Figure 3.2.2b Rule for Conversion of Actual Addresses
of General-Purpose Register Area
independently.
— — H I IL1
"0" "0" "0" "0" "0" "1"
A8
H
CCR
IL0 N Z V C
Lower operation codes
Upper bits of RP
R4 R3 R2 R1 R0
A7 A6 A5 A4 A3
to 01FF can be used as the general-
H
RP initial value
XXXXXXXX
B
b2 b1 b0
A2 A1 A0
MB89620 series