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2.4.2 Bank Type Addressing
At bank type addressing, the 16-Mbyte memory space is divided into 256 banks of 64 Kbytes each; the
upper 8-bit address is determined by specifying the bank address corresponding to each space at the bank
register, and the lower 16-bit address is specified by an instruction.
Bank register has following 5 types depending on the use.
• Program bank register (PCB)
• Data bank register (DTB)
• User stack bank register (USB)
• System stack bank register (SSB)
• Additional bank register (ADB)
n Bank registers and access space
Table 2-1 shows the access space for each bank register and the major use of it.
Table 2-1 Access Space for Each Bank Register and Major Use of Access Space
Bank Register Name
Program bank register (PCB)
Data bank register (DTB)
User stack bank register (USB)
System stack bank register
(SSB)*
Additional bank register (ADB)
*: SSB is always used as the stack at an interrupt.
CPU
Access
Space
Program
Stores instruction code, vector tables, immediate
(PC) space
data, etc.
Data (DT)
Data that can be read/written is stored, and
space
peripheral resource control registers and data
registers are accessed.
Stack (SP)
Makes stack access, such as execution of
space
PUSH/POP instruction or saving interrupt-time
registers. When the condition register stack flag
(CCR: S) is 1, SSB is used. When the condition
register stack flag is 0, USB is used*.
Additional
Stores data, etc., that cannot be stored in data
(AD) space
(DT) space
2-9
Major Use
Initial
Value At
Reset
FF
H
00
H
00
H
00
H
00
H
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