Fujitsu MB90460 Series, Hardware Manual, Page: 77 / 739

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CHAPTER 3 CPU
3.9.1 Bank Select Prefix (PCB, DTB, ADB, SPB)
A bank select prefix is placed before an instruction to select the memory space
accessed by the instruction regardless of the addressing method.
■
Bank Select Prefixes (PCB, DTB, ADB, SPB)
The memory space used for data access is defined for each addressing method. If a bank select prefix is
placed before an instruction, the memory space accessed by the instruction can be selected regardless of the
addressing method. Table 3.9-1 lists the bank select prefix codes and selected memory spaces.
If a bank select prefix is used, some instructions perform an unexpected operation.
Table 3.9-2 lists the instructions that are not affected by bank select prefix codes. Table 3.9-3 lists
instructions that require caution when they are used.
Table 3.9-1 Bank Select Prefix Codes and selected Memory Spaces
Bank select prefix Selected space
PCB Program space
DTB Data space
ADB Additional space
SPB
When the value of the S flag in the condition code register (CCR) is "0" and the
user stack space is "1", the system stack space is used.
Table 3.9-2 Instructions not affected by Bank Select Prefix Codes
Instruction type Instruction Effect of bank select prefix
String instruction
MOVS MOVSW
SCEQ SCWEQ
FIL SFILSW The bank register specified by the
operand is used whether or not a prefix is
used.
Stack
operation
PUSHW POPW
When the S flag is "0", the user stack bank
(USB) is used whether or not there is a
prefix. When the S flag is "1", the system
stack bank (SSB) is used regardless of
whether a prefix is used.
I/O access instruction
MOV A MOVX A, io
MOVW A, io
MOV io, A MOVW io, A
MOV io, #imm8 MOVW io,#imm16
MOVB A, io : bp MOVB io : bp, A
SETB io : bp CLRB io : bp
BBC io : bp, rel BBS io : bp, rel
WBTC io, bp WBTS io : bp
The I/O space (000000
H
to 0000FF
H
) is
accessed whether or not there is a
prefix.
Interrupt return
instruction
RETI
The system stack bank (SSB) is used
whether or not a prefix is used.