STV9937 datasheet(9/49 Pages) STMICROELECTRONICS

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STV9937

All OSD control registers are located in Window 0, Row 0. PictureBooSTTM control registers are

located in Window 0, Row 1. All color-boxes data are located in Window 0, Row 2.

Three formats are available: A, B and C, as described in the I²C protocol (see Section 2.1: I²C

Protocol).

All addresses (FAC and FWR bytes) are based on Formats A or B, and are written in hexadecimal

format.

2.1

I²C Protocol

The serial interface with the microcontroller is an I²C bus with 2 wires: SCL and SDA.The OSD is a

slave circuit with 2 modes: Write and Read. The slave address of the OSD is BAh in write mode and

BBh in read mode.

2.1.1

Data to Write

In the OSD, the I²C bus is used to write - read:

●

the control data

●

the character codes and their respective color codes

●

the color-boxes (8 color-boxes per window).

A color-box contains the character color, character background color and blink data. There are 8

color-boxes for each OSD window which are used to define the colors available for all the

characters of the given OSD window. 3 bits are required to code the 8 color-boxes. These bits are

the color code.

For more information, refer to Section 4.5: Character Colors on page 22.

Each character code is related to its own window, row and column. Consequently, the protocol of

the I²C transmission includes this information (window, row and column) to define the position of the

character on the screen. These 3 pieces of information about the position are transmitted in 2 bytes.

As each character on the screen has its own color code, the same protocol is used to write all the

color codes and character codes. Only the attribute bit called ‘A’ allows the character codes to be

distinguished from the color codes corresponding to one position on the screen.

The control data is also written with the same protocol using windows, rows and columns. Window

0 is reserved for control data and color codes.

2.1.2

Transmission Formats

There are 3 transmission formats to suit the amount of data to update. The transmission format is

coded in the “window/row/column” bytes.

Format A is suitable for updating small amounts of data which are allocated to different window, row

and column addresses.

Format B is recommended for updating data for the same window and the same row address, but

with a different column address and when changing the Character/Color-box attribute (bit A), or

when writing to a different I²C control register.

Format C is appropriate for updating large amounts of data from a full window or full screen. The

window, row and column addresses are incremented automatically when this format is applied.

Data is written to fill all the allocation memory of the windows.

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