
2.1 CPU
33
s Flag Change Suppression Prefix
The flag suppression code or no-change code (NCC) is used to suppress unwanted flag changes. The
NCC is placed before the instruction in which flag changes are to be suppressed, and will suppress all
flag changes resulting from that instruction. This prefix affects the T, N, Z, V and C flags.
Note that caution is required when using this prefix with the instructions shown in Table 2.1.10.
Table 2.1.10 Instructions Requiring Caution in Using Flag Change Suppression Prefix
s About Interrupt Suppressing Instructions
Table 2.1.11 lists ten types of instructions with which hardware interrupt requests are not detected, and
interrupt requests are ignored.
Table 2.1.11 Hardware Interrupt Suppressing Instructions
Thus as Figure 2.1.20 shows, when a hardware interrupt is generated during execution of one or more
of these instructions, interrupt processing will be delayed until after the execution of the first an
instruction that is not one of the above types and follows any of these instructions.
Instruction type
Instruction
Function
String instructions
MOVS
MOVSW
SCEQ
SCWEQ
FILS
FILSW
Do not use the NCC prefix with
string instructions.
Flag change instruc-
tions
AND
CCR,#imm8
OR
CCR,#imm8
The CCR will change according to
instruction specifications whether
the prefix is used or not. The effect
of the prefix will be retained for the
next instruction.
PS recovery instruc-
tions
POPW
PS
The CCR will change according to
instruction specifications whether
the prefix is used or not. The effect
of the prefix will be retained for the
next instruction.
ILM setting instruc-
tions
MOV
ILM,#imm8
The effect of the prefix will be
retained for the next instruction.
Interrupt instructions
Interrupt recovery
instructions
INT
#vct8
INT9
INT
addr16
INTP addr24
RETI
The CCR will change according to
instruction specifications whether
the prefix is used or not.
Context switching
instructions
JCTX
@A
The CCR will change according to
instruction specifications whether
the prefix is used or not.
MOV ILM,#imm8
PCB
SPB
AND CCR,#imm8
ADB
CMR
OR
CCR,#imm8
NCC
POPW PS
DTB