STE2004S datasheet(34/79 Pages) STMICROELECTRONICS

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Bus interfaces

STE2004S

34/79

Reading mode

If the R/W bit is set to logic 1 the chip outputs data immediately after the slave address. If

the D/C bit during the last write access is set to a logic 0, the byte read is the status byte.

Figure 33.

Communication protocol

4.2

Serial interfaces

STE2004S can feature three different serial synchronized interfaces with the host controller. It is

possible to select a 3-lines SPI, a 4-lines SPI or 3-line 9 bits serial interface.

4.2.1

4-lines SPI interface

The STE2004S 4-lines serial interface is a bidirectional link between the display driver and the

application supervisor. It consists of four lines: one/two for data signals (SDIN, SOUT), one for

clock signals (SCLK), one for the peripheral enable (CS) and one for mode selection (SD/C).

The serial interface is active only if the CS line is set to a logic 0. When CS line is high the serial

peripheral power consumption is zero. While CS pin is high the serial interface is kept in reset.

The STE2004S is always a slave on the bus and receives the communication clock on the SCLK

pin from the master.

Information is exchanged byte-wide. During data transfer, the data line is sampled on the positive

SCLK edge.

SD/C line status indicates whether the byte is a command (SD/C =0) or a data (SD/C =1); SD/C

line is read on the eighth SCLK clock pulse during every byte transfer.

If CS stays low after the last bit of a command/data byte, the serial interface expects the MSB of

the next byte at the next SCLK positive edge.

A reset pulse on RES pin interrupts the transmission. No data is written into the data RAM and all

the internal registers are cleared.

If CS is low after the positive edge of RES, the serial interface is ready to receive data.

Throughout SDOUT, the driver I2C slave address or the status byte can be read. The command

sequence to read the I2C slave address or the status byte is shown in

Figure 34., Figure 35.,

LR0008

01111

A0A

DRIVER ACK

WRITE MODE

READ MODE

R/W

SLAVE ADDRESS

DRIVER ACK

COMMAND WORD

CONTROL BYTE

MSB........LSB

LAST

N> 0 BYTE

DRIVER ACK

1 DC Control Byte

DATA Byte

DC Control Byte

A 0

DATA Byte

A P

01111

A1A

DRIVER ACK

MASTER ACK

DRIVER

SLAVE ADDRESS

01111

CONTROL BYTE

000

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