PCF85176 datasheet(21/43 Pages) NXP

21 / 43 page

PCF85176_1

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Product data sheet

Rev. 01 — 14 April 2010

21 of 43

NXP Semiconductors

PCF85176

Universal LCD driver for low multiplex rates

7.16.5 I2C-bus controller

The PCF85176 acts as an I2C-bus slave receiver. It does not initiate I2C-bus transfers or

transmit data to an I2C-bus master receiver. The only data output from the PCF85176 are

the acknowledge signals of the selected devices. Device selection depends on the

I2C-bus slave address, on the transferred command data and on the hardware

subaddress.

In single device applications, the hardware subaddress inputs A0, A1, and A2 are

normally tied to VSS which defines the hardware subaddress 0. In multiple device

applications A0, A1, and A2 are tied to VSS or VDD using a binary coding scheme, so that

no two devices with a common I2C-bus slave address have the same hardware

subaddress.

7.16.6 Input filters

To enhance noise immunity in electrically adverse environments, RC low-pass filters are

provided on the SDA and SCL lines.

7.16.7 I2C-bus protocol

Two I2C-bus slave addresses (0111 000 and 0111 001) are used to address the

PCF85176. The entire I2C-bus slave address byte is shown in Table 7.

The PCF85176 is a write-only device and will not respond to a read access, therefore bit 0

should always be logic 0. Bit 1 of the slave address byte that a PCF85176 will respond to,

is defined by the level tied to its SA0 input (VSS for logic 0 and VDD for logic 1).

Having two reserved slave addresses allows the following on the same I2C-bus:

Fig 15. Acknowledgement of the I2C-bus

mbc602

START

condition

clock pulse for

acknowledgement

not acknowledge

acknowledge

data output

by transmitter

data output

by receiver

SCL from

master

Table 7.

I2C slave address byte

Slave address

Bit

MSB

LSB

SA0

R/W

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