PCF8545ATT datasheet(28/51 Pages) NXP

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NXP Semiconductors

PCF8551

Universal 36 × 4 LCD segment driver

Slave address

Bit

MSB

LSB

R/W

Table 12. I2C slave address byte

The least significant bit of the slave address byte is bit R/W (see Table 13).

R/W

Description

write data

read data

Table 13. R/W-bit description

10.2 SPI-bus interface of the PCF8551B

Data transfer to the device is made via a 3-line SPI-bus (see Table 14). There is no

dedicated output data line. The SPI-bus is initialized whenever the chip enable line pin

CE is pulled down.

Symbol Function

Description

chip enable input[1]; active LOW when HIGH, the interface is reset

SCL

serial clock input

input may be higher than VDD

SDIO

serial data input/output

input data are sampled on the rising edge of SCL,

output data are valid after the falling edge of SCL

Table 14. Serial interface

[1]

The chip enable must not be wired permanently LOW.

10.2.1 Data transmission

The chip enable signal is used to identify the transmitted data. Each data transfer is a

byte with the Most Significant Bit (MSB) sent first.

The transmission is controlled by the active LOW chip enable signal CE. The first byte

transmitted is the register address comprising of the address pointer and the R/W bit.

aaa-011938

data bus

DATA

Figure 19. Data transfer overview

Bit

Symbol

Value

Description

data read or write selection

write data

R/W

read data

Table 15. Address byte definition

PCF8551

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Product data sheet

Rev. 3.1 — 3 May 2021

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