PCF8545 datasheet(37/68 Pages) NXP

37 / 68 page

NXP Semiconductors

PCF8545

Universal LCD driver for multiplex rates up to 1:8

mbc622

SDA

SCL

STOP condition

SDA

SCL

START condition

Figure 27. Definition of START and STOP conditions

8.2.3 System configuration

A device generating a message is a transmitter, a device receiving a message is the

receiver. The device that controls the message is the controller and the devices which

are controlled by the controller are the targets. The system configuration is shown in

Figure 28.

mga807

SDA

SCL

CONTROLLER

TRANSMITTER/

RECEIVER

CONTROLLER

TRANSMITTER

TARGET

TRANSMITTER/

RECEIVER

TARGET

RECEIVER

CONTROLLER

TRANSMITTER/

RECEIVER

Figure 28. System configuration

8.2.4 Acknowledge

The number of data bytes transferred between the START and STOP conditions from

transmitter to receiver is unlimited. Each byte of 8 bits is followed by an acknowledge

cycle.

• A target receiver which is addressed must generate an acknowledge after the reception

of each byte.

• Also a controller receiver must generate an acknowledge after the reception of each

byte that has been clocked out of the target transmitter.

• The device that acknowledges must pull-down the SDA line during the acknowledge

clock pulse, so that the SDA line is stable LOW during the HIGH period of the

acknowledge related clock pulse (set-up and hold times must be considered).

• A controller receiver must signal an end of data to the transmitter by not generating an

acknowledge on the last byte that has been clocked out of the target. In this event, the

transmitter must leave the data line HIGH to enable the controller to generate a STOP

condition.

Acknowledgement on the I2C-bus is shown in Figure 29.

PCF8545

All information provided in this document is subject to legal disclaimers.

Product data sheet

Rev. 2 — 4 October 2021

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