PCF8532 datasheet(23/49 Pages) NXP

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PCF8532

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Product data sheet

Rev. 2 — 10 February 2011

23 of 49

NXP Semiconductors

PCF8532

Universal LCD driver for low multiplex rates

7.16.5 I2C-bus controller

The PCF8532 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 PCF8532 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 application, the hardware subaddress inputs A0 and A1 are normally tied

to VSS which defines the hardware subaddress 0. In multiple device applications A0

and A1 are tied to VSS or VDD in accordance with a binary coding scheme such 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 reserved for the PCF8532.

The least significant bit of the slave address that a PCF8532 responds to is defined by the

level tied at its input SA0. The PCF8532 is a write only device and does not respond to a

read access. Two types of PCF8532 can be distinguished on the same I2C-bus which

allows:

• Up to 8 PCF8532 on the same I2C-bus for very large LCD applications

• The use of two types of LCD multiplex on the same I2C-bus.

The I2C-bus protocol is shown in Figure 17. The sequence is initiated with a START

condition (S) from the I2C-bus master which is followed by one of the two PCF8532 slave

addresses available. All PCF8532 with the corresponding SA0 level acknowledge in

parallel to the slave address, but all PCF8532 with the alternative SA0 level ignore the

whole I2C-bus transfer.

Fig 16. Acknowledgement on the I2C-bus

mbc602

START

condition

clock pulse for

acknowledgement

not acknowledge

acknowledge

data output

by transmitter

data output

by receiver

SCL from

master

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