PCF8577C datasheet(8/28 Pages) PHILIPS

8 / 28 page

1998 Jul 30

Philips Semiconductors

Product speciﬁcation

LCD direct/duplex driver with

I2C-bus interface

PCF8577C

6.7

Power-on reset

At power-on reset the PCF8577C resets to a defined

starting condition as follows:

1. Both backplane outputs are set to VSS in master mode;

to 3-state in cascade mode

2. All segment outputs are set to VSS

3. The segment byte registers and control register are

cleared

4. The I2C-bus interface is initialized.

6.8

Slave address

The PCF8577C slave address is shown in Fig.6.

Before any data is transmitted on the I2C-bus, the device

which should respond is addressed first. The addressing is

always done with the first byte transmitted after the start

procedure.

Fig.6 PCF8577C slave address.

0 11101 00

SLAVE ADDRESS

MGA731

6.9

I2C-bus protocol

The PCF8577C I2C-bus protocol is shown in Fig.7.

The PCF8577C is a slave receiver and has a fixed slave

address (see Fig.6). All PCF8577Cs with the same slave

address acknowledge the slave address in parallel.

The second byte is always the control byte and is loaded

into the control register of each PCF8577C connected to

the I2C-bus. All addressed devices acknowledge the

control byte. Subsequent data bytes are loaded into the

segment registers of the selected device. Any number of

data bytes may be loaded in one transfer and in an

expanded system rollover of the SBV from 111 111 to

000 000 is allowed. If a stop (P) condition is given after the

control byte acknowledge the segment data will remain

unchanged. This allows the BANK bit to be toggled without

changing the segment register contents. During loading of

segment data only the selected PCF8577C gives an

acknowledge. Loading is terminated by generating a stop

(P) condition.

Fig.7 I2C-bus protocol.

SLAVE ADDRESS

SEGMENT DATA

acknowledge by

all PCF8577C

R/W

auto increment

segment byte vector

MGA732

SEGMENT

BYTE VECTOR

acknowledge by

all PCF8577C

acknowledge by

selected PCF8577C only

msb

lsb

n bytes

control byte

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