Fujitsu CM71-00101-5E User Manual

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CHAPTER 4  RESET AND "EIT" PROCESSING

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Interrupts originate independently of the instruction sequence. They are processed by saving the necessary

information to resume the currently executing instruction sequence, and then starting the processing routine

corresponding to the type of interrupt that has occurred.

Instructions loaded and executing in the CPU before the interrupt will be executed to completion, however,

any instructions loaded in the pipeline after the interrupt will be canceled. After completion of interrupt

processing, therefore, execution will return to the next instruction following the generation of the interrupt

signal.

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There are two types of interrupt sources.

•

User interrupts (See Section "4.3.1  User Interrupts")

•

Non-maskable interrupts (NMI) (See Section "4.3.2  Non-maskable Interrupts (NMI)")

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To enable resumption of processing when interrupts occur during stepwise division programs, intermediate

data is placed in the program status (PS), and saved to the stack. Therefore, if the interrupt processing

program overwrites the contents of the "PS" data in the stack, the processor will resume executing the

stepwise division instruction following the completion of interrupt processing, however the results of the

division calculation will be incorrect.