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STV9427

HIGH SPEED MULTISYNCH ON-SCREEN DISPLAY FOR MONITOR

STMicroelectronics 

STV9427 - STV9428 - STV9429

FUNCTIONAL DESCRIPTION

The STV9427/28/29 display processor operation is

controlled by a host MCU via the I2C interface. It is

fully programmable through internal read/write reg-

isters and performs all the display functions by

generating pixels from data stored in its internal

memory. After the page downloading from the

MCU, the STV9427/28/29 refreshes screen by

its built in processor, without any MCU control

(access). In addition, the host MCU has a direct

access to the on chip 1Kbytes RAM during the

display of the current page to make any update

of its contents.

With the STV9427/28/29, a page displayed on the

screen is made of several strips which can be of 2

types : spacing or character and which are de-

scribed by a table of descriptors and character

codes in RAM. Several pages can be downloaded

at the same time in the RAM and the choice of the

current display page is made by programming the

DISPLAY CONTROL register.

I - Serial Interface

The 2-wires serial interface is an I2C interface. To

be connected to the I2C bus, a device must own its

slave address ; the slave address of the

STV9427/28/29 is BA (in hexadecimal).

A6 A5 A4 A3 A2 A1 A0 R/W

1

0

1

1

1

0

1

Figure 4 : MCU I2C Write Operation

I.1 - Data Transfer in Write Mode

The host MCU can write data into the

STV9427/28/29 registers or RAM.

To write data into the STV9427/28/29, after a start,

the MCU must send (Figure 4) :

- First, the I2C address slave byte with a low level

for the R/W bit,

- The two bytes of the internal address where the

MCU wants to write data(s),

- The successive bytes of data(s).

All bytes are sent MSB bit first and the write data

transfer is closed by a stop.

Each byte is synchronously transfered at each

HSYNC period.

I.2 - Data Transfer in Read Mode

The host MCU can read data from the

STV9427/28/29 registers, RAM or ROM.

To read data from the STV9427/28/29 (Figure 5),

the MCU must send 2 different I2C sequences. The

first one is made of I2C slave address byte with R/W

bit at low level and the 2 internal address bytes.

The second one is made of I2C slave address byte

with R/W bit at high level and all the successive

data bytes read at successive addresses starting

from the initial address given by the first sequence.

Each byte is synchronously transfered at each

HSYNC period. The first data byte, in read mode,

is available one Hsync period after the acknow-

ledge of the address byte.

SCL

SDA

Start

I2C Slave Address

R/W

A7 A6 A5 A4 A3 A2 A1 A0

-

ACK

LSB Address

ACK

- A13 A12 A11 A10 A9 A8

MSB Address

ACK

SCL

SDA

D7 D6 D5 D4 D3 D2 D1 D0

D7 D6 D5 D4 D3 D2 D1 D0

Data Byte 1

ACK

Data Byte 2

ACK

D7 D6 D5 D4 D3 D2 D1 D0

Data Byte n

ACK

Stop

Figure 5 : MCU I2C Read Operation

SCL

SDA

Start

I2C Slave Address

R/W

A7 A6 A5 A4 A3 A2 A1 A0

-

ACK

LSB Address

ACK

- A13 A12 A10 A10 A9 A8

MSB Address

ACK

Stop

SCL

SDA

Start

I2C Slave Address

R/W

D7 D6 D5 D4 D3 D2 D1 D0

D7 D6 D5 D4 D3 D2 D1 D0

ACK*

Data Byte 1

ACK

Data Byte n

ACK

Stop

Note : The first data bit out (D7) is valid after one scanline period.

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