Prefix Codes - Fujitsu MB90390 Series Hardware Manual

2.9

Prefix Codes

Placing a prefix code before an instruction partially changes the operation of the
instruction. Three types of prefix codes can be used: bank select prefix, common
register bank prefix, and flag change disable prefix.
■ Bank Select Prefix
The memory space used for accessing data is determined for each addressing mode.
When a bank select prefix is placed before an instruction, the memory space used for accessing data by that
instruction can be selected regardless of the addressing mode.
Table 2.9-1 lists the bank select prefixes.
Table 2.9-1 Bank Select Prefix
Bank select prefix
Use the following instructions with care:
●
String instructions (MOVS, MOVSW, SCEQ, SCWEQ, FILS, FILSW)
The bank register specified by an operand is used regardless of the prefix.
●
Stack manipulation instructions (PUSHW, POPW)
SSB or USB is used according to the S flag regardless of the prefix.
●
I/O access instructions
The I/O space of the bank is used regardless of the prefix.
●
Flag change instructions (AND CCR,#imm8, OR CCR,#imm8)
The instruction is executed normally, but the prefix affects the next instruction.
●
POPW PS
SSB or USB is used according to the S flag regardless of the prefix. The prefix affects the next instruction.
●
MOV ILM,#imm8
The instruction is executed normally, but the prefix affects the next instruction.
PCB
DTB
ADB
SPB Either the SSP or USP space is used according to the stack flag value.
MOV A, io / MOV io, A /MOVX A, io / MOVW A, io /MOVW io, A / MOV io, #imm8
MOV io, #imm16 / MOVB A, io:bp / MOB io:bp, A /SETB io:bp / CLRB io:bp
BBC io:bp, rel / BBS io:bp, rel WBTC, WBTS
Space selected
PC space
Data space
AD space
CHAPTER 2 CPU
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