PCF8593 datasheet(11/28 Pages) PHILIPS

11 / 28 page

1997 Mar 25

Philips Semiconductors

Product speciﬁcation

Low power clock/calendar

PCF8593

Fig.9 Selection of alarm weekdays.

handbook, full pagewidth

765

4321

MSB

LSB

MBD816

memory location 0E (alarm weekday/month)

weekday 0 enabled when set

weekday 1 enabled when set

weekday 2 enabled when set

weekday 3 enabled when set

weekday 4 enabled when set

weekday 5 enabled when set

weekday 6 enabled when set

not used

7.7

Timer

The timer (location 07) is enabled by setting the

control/status register = XX0X X1XX. The timer counts up

from 0 (or a programmed value) to 99. On overflow, the

timer resets to 0. The timer flag (LSB of control/status

reset by software. The inverted value of this flag can be

transferred to the external interrupt by setting bit 3 of the

alarm control register.

Additionally, a timer alarm can be programmed by setting

the timer alarm enable (bit 6 of the alarm control register).

When the value of the timer equals a pre-programmed

value in the alarm timer register (location 0F), the alarm

flag is set (bit 1 of the control/status register). The inverted

value of the alarm flag can be transferred to the external

interrupt by enabling the alarm interrupt (bit 6 of the alarm

control register).

Resolution of the timer is programmed via the 3 LSBs of

the alarm control register (see Fig.11, Alarm and timer

Interrupt logic diagram).

7.8

Event counter mode

Event counter mode is selected by bits 4 and 5 which are

logic 1, 0 in the control/status register. The event counter

mode is used to count pulses externally applied to the

oscillator input (OSCO left open-circuit). The event counter

stores up to 6 digits of data, which are stored as

6 hexadecimal values located in locations 1, 2, and 3.

Thus, up to 1 million events may be recorded.

An event counter alarm occurs when the event counter

registers match the value programmed in locations 9, A,

and B, and the event alarm is enabled (bits 4 and 5 which

are logic 0, 1 in the alarm control register). In this event,

the alarm flag (bit 1 of the control/status register) is set.

The inverted value of this flag can be transferred to the

interrupt pin (pin 7) by setting the alarm interrupt enable in

the alarm control register. In this mode, the timer

(location 07) increments once for every one, one-hundred,

ten thousand, or 1 million events, depending on the value

programmed in bits 0,1 and 2 of the alarm control register.

In all other events, the timer functions are as in the clock

mode.

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