PCD3745AP datasheet(15/32 Pages) PHILIPS

15 / 32 page

1999 Feb 02

Philips Semiconductors

Product speciﬁcation

8-bit microcontroller with 4.5 kbytes OTP

memory and 32 kHz real-time clock

PCD3745A

handbook, full pagewidth

8-bit internal bus

peripheral

counter

control

C1:

16-BIT COUNTER

C2:

16-BIT COUNTER

EC1 EC1I

C1F

CLK1

CLK2

CE/T0

C2F

INTERRUPT

LOGIC

CPU

interrupt

RTC,timer and

external interrupts

counter

interrupts

RTC

PCD3745A

TIMER

EC2 EC2I

timer overflow

MSC331

Fig.5 Operation of the 16-bit counters used in metering applications.

THE RTC, COUNTER 1 AND COUNTER 2

INTERRUPTS

As well as the CE/T0 interrupt three additional interrupt

events are defined which have the same effect as an

external interrupt (see

“PCD33xxA family data sheet”).

• Real Time Clock. This interrupt is controlled by the

Clock Interrupt Flag (CIF) and the Enable Clock

Interrupt (ECI) bit both of which reside in the Clock

Control Register (see Tables 3 and 4)

• Counter 1. This interrupt is controlled by the Counter 1

Interrupt Flag (C1F) and the Enable Counter 1 Interrupt

Flag (EC1I) both of which are located in the Peripheral

Counter Control Register (see Tables 8 and 9)

• Counter 2. This interrupt is controlled by the Counter 2

Interrupt Flag (C2F) and the Enable Counter 2 Interrupt

Flag (EC2I) both of which are located in the Peripheral

Counter Control Register (see Tables 8 and 9).

To use these interrupt sources the external interrupt must

be enabled (EN I). Interrupt servicing is exactly the same

as for an external interrupt. The interrupt routine must

include instructions that will determine the interrupt source

and remove the cause of the derivative interrupt by

explicitly clearing CIF, C1F or C2F.

By not clearing these flags the microcontroller is unable to

detect interrupts of the same type. In the interrupt routine

the CE/T0 interrupt has to be deduced from the fact that

neither CIF or C1F or C2F is set. If the specific interrupt is

not used, CIF, C1F or C2F may be directly tested by the

program. Obviously, CIF, C1F or C2F can also be asserted

under program control, e.g. to generate a software

interrupt.

Although the clock interrupt and Counter 1 and Counter 2

are part of a derivative function they are linked to the

external interrupt (see Fig.6).

A clock, Counter 1 or Counter 2 interrupt request is

serviced under the following circumstances:

• No interrupt routine is being processed

• No external interrupt request is pending

• The enable clock interrupt and enable Counter 1 and

Counter 2 interrupt bit in the derivative Clock Control

respectively is set.

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