Prefix Code - Fujitsu F2MC-16LX Hardware Manual

2.4

Prefix Code

A part of instruction operation can be changed by placing the prefix code before the
instruction.
Three types of prefix codes can be used:
• The bank select prefix
• The common register bank prefix
• The flag change suppression prefix.
Bank Select Prefix
Memory spaces used to access data are defined for each addressing mode.
Placing the bank select prefix before the instruction allows the instruction to select the memory space used
for the data access regardless of addressing mode.
Table 2.4-1 shows the relation between the bank select prefix and the space to be selected.
Table 2.4-1 Bank Select Prefix
Bank Select Prefix
Be careful when using the following instructions:
String instruction (MOVS,MOVSW,SCEQ,SCWEQ,FILS,FILSW)
The bank register specified by the operand is used regardless of the prefix.
Stack operation instruction (PUSHW,POPW)
The SSB or the USB is used according to the S flag regardless of the prefix.
I/O Access instruction
MOVA A,io/MOV io,A/MOVX A,io/MOVW A,io/MOVW io,A
MOV io,#imm8/MOVW io,#imm8/MOBV A,io:bp/MOVB io:bp,A
SETB io:bp/CLRB io:bp/BBC io:bp,rel/BBS io:bp,rel WBTC
WBTS
The bank I/O space is used regardless of the prefix presence or absence.
Flag change instruction (AND CCR,#imm8,OR CCR,#imm8)
The instruction operation is normal although the prefix continuously affects the next instruction.
PCC PC space
DTB Data space
ADB AD space
SPB The SSP or USP space is used according to the stack flag value.
Selected Space
CHAPTER 2 CPU
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