PCF8564AU datasheet(23/48 Pages) NXP

23 / 48 page

PCF8564A

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Product data sheet

Rev. 3 — 26 August 2013

23 of 48

NXP Semiconductors

PCF8564A

Real time clock and calendar

10. I2C-bus protocol

10.1 Addressing

Before any data is transmitted on the I2C-bus, the device which should respond is

addressed first. The addressing is always carried out with the first byte transmitted after

the start procedure.

The PCF8564A 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.

Two slave addresses are reserved for the PCF8564A:

Read: A3h (1010 0011)

Write: A2h (1010 0010)

The PCF8564A slave address is shown in Figure 14.

10.2 Clock and calendar READ or WRITE cycles

Figure 16, Figure 17, and Figure 18 show the I2C-bus configuration for the different

PCF8564A READ and WRITE cycles. The word address is a 4-bit value that defines

which register is to be accessed next. The upper four bits of the word address are not

used.

Fig 15. Slave address

Fig 16. Master transmits to slave receiver (WRITE mode)

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