STV9420 datasheet(6/16 Pages) STMICROELECTRONICS

6 / 16 page

FUNCTIONAL DESCRIPTION

The STV9420/21 display processor operation is

controlled by a host MCU via the I

2C interface. It is

fully programmable through 8 internal read/write

registers (12 for STV9421) and performs all the

display functions by generating pixels from data

stored in its internal memory. After the page down-

loading from the MCU, the STV9420/21 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 STV9420/21, 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

CONTROL register.

I - Serial Interface

The 2-wires serial interface is an I

2C interface. To

be connected to the I

2C bus, a device must own its

sl ave ad dr ess ; the sla ve address of t he

STV9420/21 is BA (in hexadecimal).

R/W

10111

I.1 - Data Transfer in Write Mode

The host MCU can write data into the STV9420/21

registers or RAM.

To write data into the STV9420/21, after a start, the

MCU must send (Figure 3) :

- First, the I

2C 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 MS bit first and the write data

transfer is closed by a stop.

I.2 - Data Transfer in Read Mode

The host MCU can read data from the STV9420/21

registers, RAM or ROM.

To read data from the STV9420/21 (Figure 4), the

MCU must send 2 different I

2C sequences.

The first one is made of I

2C slave address byte with

R/W bit at low level and the 2 internal address

bytes.

The second one is made of I

2C 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.

SCL

SDA

R/W

I1C Slave Address

ACK

LSB Address

ACK

MSB Address

ACK

Start

A13 A12 A10 A10 A9

Stop

SCL

SDA

R/W

I1C Slave Address

ACK

Data Byte n

ACK

Start

Stop

Data Byte 1

Figure 4 : STV9420/I

2C Read Operation

SCL

SDA

R/W

A13

A12

A11

A10

I2C Slave Address

ACK

LSB Address

ACK

MSB Address

ACK

Start

ACK

Data Byte 1

Data Byte 2

ACK

Data Byte n

Stop

SCL

SDA

Figure 3 : STV9420/I

2C Write Operation

STV9420 - STV9421

6/16

STV9420 Datasheet(PDF) 6 Page - STMicroelectronics

STV9420 Datasheet(HTML) 6 Page - STMicroelectronics

Html Pages

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16

Datasheet Download

Link URL