1997 Mar 28

9

Philips Semiconductors

Product specification

Clock/calendar with Power Fail Detector

PCF8573

9.1

Addressing

always done with the first byte transmitted after the start procedure.

The clock/calendar acts as a slave receiver or slave transmitter. Therefore the clock signal SCL is only an input signal,

but the data signal SDA is a bidirectional line.

The clock/calendar slave address is shown in Fig.7. Bits A0 and A1 correspond to the two hardware address pins A0 and

9.2

Clock/calendar READ/WRITE cycles

The write cycle is used to set the time counter, the alarm register and the flags. The transmission of the clock/calendar

address is followed by the MODE-POINTER-word which contains a CONTROL-nibble (Table 3) and an

ADDRESS-nibble (Table 4). The ADDRESS-nibble is valid only if the preceding CONTROL-nibble is set to EXECUTE

ADDRESS. The third transmitted word contains the data to be written into the time counter or alarm register.

Fig.7 Slave address.

Fig.8 Master transmitter transmits to clock/calendar slave receiver.