PCF85263ATLSLASHA datasheet(63/102 Pages) NXP

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NXP Semiconductors

PCF85263A

Tiny RTC/Calendar with Alarm Function, Battery Switch-Over, Time Stamp Input, and I2C-bus

9 Interface protocol

The PCF85263A uses the I2C interface for data transfer. The interface protocol determines the interpretation of

the data.

9.1 Write protocol

After the I2C target address is transmitted, the PCF85263A requires that the register address pointer is defined.

It can take the value 00h to 2Fh. Values outside that range results in the transfer being ignored. However, the

target still responds with acknowledge pulses.

After the register address is transmitted, write data is transmitted. The minimum number of data write bytes is 0

and the maximum number is unlimited. After each write, the address pointer increments by one. After address

2Fh, the address pointer will roll over to 00h.

• I2C START condition

• I2C target address + write

• Register address

• Write data

• :

• Write data

• I2C STOP condition (An I2C RE-START condition is also possible)

9.2 Read protocol

When reading the PCF85263A, reading starts at the current position of the address pointer. The address pointer

for read data must first be defined by a write sequence.

• I2C START condition

• I2C target address + write

• register address

• I2C STOP condition (An I2C RE-START condition is also possible)

After setting the address pointer, a read can be executed. After the I2C target address is transmitted, the

PCF85263A will immediately output read data. After each read, the address pointer increments by one. After

address 2Fh, the address pointer will roll over to 00h.

• I2C START condition

• I2C target address + read

• Read data (controller sends acknowledge bit)

• :

• Read data (controller sends not-acknowledge bit)

• I2C STOP condition (An I2C RE-START condition is also possible)

The controller must indicate that the last byte has been read by generating a not-acknowledge after the last

read byte.

PCF85263A

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Product data sheet

Rev. 5.4 — 12 December 2025

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