Figure 3.3 Register Bank Structure; General-Purpose Registers - Fujitsu F2MC-8L MB89620 Series Hardware Manual

3
3.

General-purpose Registers

The general-purpose registers are a memory block made up of banks, with 8 × 8-bit
registers per bank.
The register bank pointer (RP) is used to specify the register bank.
In functional terms, a total of 32 banks are available. If internal RAM is insufficient for
all banks, the remaining banks can be expanded in external RAM.
Register banks are valid for interrupt processing, vector call processing, and
subroutine calls.
n Structure of General-purpose Registers
• The general-purpose registers are 8 bits and located in the register banks of the general-
purpose register area (in RAM).
• One bank contains eight registers (R0 to R7) and up to a total of 32 banks. However, the
number of banks available for general-purpose registers is limited on some products if
internal RAM only is used.
• The register bank currently in use is specified by the register bank pointer (RP). The lower
three bits of the operation code specify general-purpose register 0 (R0) to general-purpose
register 7 (R7).
Figure 3.3 shows the register bank structure.
*: The top address of a register bank = 0100
Reference: See Section 3.1.1, "Special Areas" for the general-purpose register area available for each
42
CHAPTER 3 CPU
100 *
H R0
R1
R2
R3
R4
R5
R6
R7
108 *
H
R0
:
R7
:
:
:
1F8 *
H
R0
:
1FF
R7
H

Figure 3.3 Register Bank Structure

product.
Lower 3 bits of
the operation code


000


001


010
Bank 0

(RP="00000---

011


100


101


110 


111


000

Bank 1
: 
(RP="00001---


111
:
Bank 2
:
to
:
Bank 30


000

Bank 31

:
(RP="11111---


111
+ 8 × (upper 5 bits of RP)
H







")
B





32 banks

 (RAM area)

The number of banks is limited

on available RAM size.





")
B











")
B

MB89620 series