NEC PD78P214 Manuale Utente

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Chapter 12 Interrupt Functions

12.4 MACRO SERVICE FUNCTION

12.4.1 Macro Service Outline

Macro service is one of the interrupt handling methods. When a vectored interrupt is processed, the contents of
the program counter (PC) and the program status word (PSW) are saved in the stack and the PC is loaded with the
vector address retrieved from the vector table. With the macro service function, a different type of processing
(mainly data transfer) is performed. This type of processing can respond to an interrupt request quickly. Moreover,
it transfers data much faster than the program does, shortening the required processing time significantly.

With the macro service function, a vectored interrupt can be generated after processing has been performed a
specified number of times, so that the vectored interrupt program can be simplified.

Fig. 12-14 Differences between a Vectored Interrupt and Macro Service

Notes 1. This timing chart applies when the register bank switching function is used and the registers are loaded with the initial values in

advance.

2. The PC and PSW contents are saved in the stack and the PC is loaded with the vector address.

Macro service

Vectored interrupt

Note 1

Vectored interrupt

Macro service
processing

Main routine

Note 2

SEL
RBn

Interrupt
processing

Main routine

Restores
PC, PSW

Note 2

Saves
general
registers

Initializes
general
registers

Interrupt
processing

Restores
general
registers

Restores
PC, PSW

Main routine

Interrupt request occurs

Main
routine