General-Purpose Registers; Configuration Of The General-Purpose Registers - Fujitsu F2MC-8L F202RA Hardware Manual

CHAPTER 3 CPU
3.3

General-Purpose Registers

The general-purpose registers are memory blocks. Eight 8-bits comprise a bank.
The register bank pointer (RP) specifies a register bank.
Although up to 32 banks can be used, some banks can be expanded onto external RAM
if the capacity of internal RAM is not sufficient for all 32 banks.
The general-purpose registers are effective for processing interrupts, vector calls, or
subroutine calls.
■

Configuration of the General-purpose Registers

• Each general-purpose register consists of 8 bits. The general-purpose registers are placed in the register
banks at the general-purpose register area (on RAM).
• One bank contains eight registers (R0 to R7), and up to 32 banks can be used. However, some models
restrict the number of usable banks when only internal RAM is used.
• The register bank pointer (RP) specifies the register bank being used. The lower three bits of an
operation code indicate general-purpose register 0 (R0) to general-purpose register 7 (R7).
Figure 3.3-1 shows the configuration of the register banks.
100 *
H
108 *
H
1F8 *
H
1FF *
H
*: Address at the top of the register banks = 0100
For details on the general-purpose register area on each model, see Section "3.1.1 Specific-purpose Areas ".
32
Figure 3.3-1 Configuration of Register Bank
R0 000
R1 001
R2 010
R3 011
Bank 0
R4 100
(RP=00000---
R5 101
R6 110
R7 111
R0 000
R1 001
Bank 1
. .
. .
(RP=00001---
R7 111
. .
Bank 2
. .
. . . .
to
. .
Bank 30
R0 000
. .
. .
Ban 31
(RP=11111---
R7 111
)
B
32 banks (on the RAM area)
The number of usable banks
)
is dependent on the size
B
of the usable RAM area.
)
B
+ 8 × (upper 5 bits of RP)
H