Restrictions On Prefix Code - Fujitsu MB90895 Series Hardware Manual

3.4.4

Restrictions on Prefix Code

The use of the prefix codes is restricted as follows:
• No interrupt request is accepted during execution of a prefix code and interrupt
inhibit instruction.
• When a prefix code precedes an interrupt inhibit instruction, The effect of the prefix
code is delayed.
• When conflicting prefix codes are used in succession, the last prefix code is enabled.
I Prefix Code and Interrupt Inhibit Instruction
The interrupt inhibit instruction and prefix code are restricted as shown below.
Table 3.4-6 Prefix Code and Interrupt Inhibit Instruction
Instruction that does not
accept interrupt request
G
Interrupt Inhibition
Even if generated, an interrupt request is not accepted during execution of a prefix code and interrupt
inhibit instruction. The interrupt is processed when any other instruction is executed after execution of a
prefix code or interrupt inhibit instruction.
The generation of interrupt request
Prefix Code
PCB
DTB
ADB
SPB
CMR
NCC
Figure 3.4-1 Interrupt Inhibition
Interrupt inhibit instruction
Interrupt/Hold Inhibit Instruction (instruction
that delays effect of prefix code)
MOV ILM,#imm8
OR CCR,#imm8
AND CCR,#imm8
POPW PS
a
Interrupt requests (a) Normal instruction
CHAPTER 3 CPU
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