PCF8583 datasheet(21/28 Pages) PHILIPS

21 / 28 page

1997 Jul 15

Philips Semiconductors

Product speciﬁcation

Clock/calendar with 240

× 8-bit RAM

PCF8583

Fig.21 I2C-bus timing diagram; rise and fall times refer to VIL and VIH.

handbook, full pagewidth

PROTOCOL

SCL

SDA

MBD820

BIT 0

LSB

(R/W)

t HD;STA

SU;DAT

HD;DAT

VD;DAT

t SU;STO

BUF

SU;STA

LOW

t HIGH

1 / f SCL

START

CONDITION

(S)

BIT 7

MSB

(A7)

BIT 6

(A6)

ACKNOWLEDGE

(A)

STOP

CONDITION

(P)

14 APPLICATION INFORMATION

14.1

Quartz frequency adjustment

14.1.1

METHOD 1: FIXED OSCI CAPACITOR

By evaluating the average capacitance necessary for the

application layout a fixed capacitor can be used.

The frequency is best measured via the 1 Hz signal

available after power-on at the interrupt output (pin 7).

The frequency tolerance depends on the quartz crystal

tolerance, the capacitor tolerance and the

device-to-device tolerance (on average

±5 × 10−6).

Average deviations of

±5 minutes per year can be

achieved.

14.1.2

METHOD 2: OSCI TRIMMER

Using the alarm function (via the I2C-bus) a signal faster

than 1 Hz can be generated at the interrupt output for fast

setting of a trimmer.

Procedure:

• Power-on

• Initialization (alarm functions).

Routine:

• Set clock to time T and set alarm to time T + dT

• At time T + dT (interrupt) repeat routine.

14.1.3

METHOD 3:

Direct measurement of OSC out (accounting for test probe

capacitance).

The PCF8583 slave address has a fixed combination 1010

as group 1.

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