Bank Addressing - Fujitsu MB90335 Series Hardware Manual

MB90335 Series
2.4

Bank Addressing

In the bank method, the 16 M byte space is divided into 256 of 64 K byte banks. The
following five bank registers are used to specify the banks corresponding to each
space:
• Program counter bank register (PCB)
• Data bank register (DTB)
• User stack bank register (USB)
• System stack bank register (SSB)
• Additional data bank register (ADB)
■ Bank Addressing
●
Program counter bank register (PCB)
The 64Kbyte bank specified by the program counter bank register (PCB) is called a program (PC) space.
The PC space typically contains instruction codes, vector tables, and immediate data.
●
Data bank register (DTB)
The 64Kbyte bank specified by the data bank register (DTB) is called a data (DT) space. The DT space
typically contains readable/ writable data, and control/data registers for internal and external resources.
●
User stack bank register (USB) and System stack bank register (SSB)
The 64Kbyte bank specified by the user stack bank register (USB) or system stack bank register (SSB) is
called a stack (SP) space. The SP space is accessed when a stack access occurs during a push/pop
instruction or interrupt register saving. The S flag in the condition code register determines which stack
space is to be accessed.
●
Additional data bank register (ADB)
The 64Kbyte bank specified by the Additional data bank register (ADB) is called an additional (AD) space.
The AD space typically contains data that cannot fit into the DT space.
Table 2.4-1 lists the default spaces used in each addressing mode, which are pre-determined to improve
instruction coding efficiency. To use a non-default space for an addressing mode, specify a prefix code
corresponding to a bank before the instruction. This enables access to the bank space corresponding to the
specified prefix code.
By resetting, the DTB, USB, SSB, and ADB are initialized to 00
specified by the reset vector. After reset, the DT, SP, and AD spaces are allocated in bank 00
00FFFF
H
CM44-10137-6E
), and the PC space is allocated in the bank specified by the reset vector.
FUJITSU MICROELECTRONICS LIMITED
CHAPTER 2 CPU
2.4 Bank Addressing
. The PCB is initialized to a value
H
(000000
H
to
H
25