UPD75236GJ 데이터 시트보기 (PDF) - NEC => Renesas Technology

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UPD75236GJ

4-BIT SINGLE-CHIP MICROCOMPUTER

NEC => Renesas Technology 

µPD75236

(3) Interrupt status flags (IST1, IST0)

The interrupt status flag is a 2-bit flag to store the status of the processing currently being executed.

(Refer to Table 5-3 IST1 and IST0 Interrupt Servicing Status for details.)

Table 3-4 Interrupt Status Flag Directive Contents

IST 1

0

0

1

1

IST0

0

1

0

1

Status of Processing

being Executed

Servicing Contents and Interrupt Control

Status 0

Normal program being executed. All interrupts acknowledgeable.

Status 1

Low or high interrupt being executed. Only high interrupt acknowledgeable.

Status 2

High interrupt being executed. All interrupts non-acknowledgeable.

—

Setting disable

The interrupt priority control circuit (see Fig. 5-1 Interrupt Control Circuit Block Diagram) identifies the

interrupt status flag contents and executes multiple interrupt control.

If the interrupt is acknowledged, the IST1 and IST0 contents are saved to the stack memory as part of

PSW and are automatically changed to the status higher by one level and the values prior to interruption

by RETI instruction are restored.

The interrupt status flag can be operated by the memory manipulation instruction and the processing

status being executed can be changed by program control.

Note Before operating this flag, be sure to disable interruption by executing DI instruction and enable

interruption by execution EI instruction after operation.

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