UPD6708 datasheet(49/72 Pages) NEC

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µPD6708

8.2

Interrupt Service Routine

This routine is used when an interrupt request is generated from the

µPD6708 (when IRQ pin becomes high). This routine

reads the contents of the return code, performs flag setting, and reads receive data.

Notes 1.

See 8.3.3.

See 8.3.4.

See 8.3.5.

Start

Disable interrupts

from PD6708

Is SIO register used?

Save value of I/O port which controls

PD6708 C/D and

R/W pins, and value of SIO register in host controller

Read STR

Return code classification

Master reception

processing

routine Note 3

Master

transmission

processing

routine Note 1

Slave data

transmission

processing

routine Note 2

Master?

Slave reception

processing

routine

Broadcast

reception

processing

routine

Restore value of I/O port which controls

PD6708 C/D

and R/W pins, and value of SIO register in host controller

Enable interrupts

from

PD6708

End

RETI

This processing is not necessary

if interrupts are disabled when

SIO is used in the main routine.

Most significant 2 bits

of return code

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