STV9936P datasheet(8/48 Pages) STMICROELECTRONICS

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STV9936P/S

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All control registers are located in Window 0, Row 0. All color-box data is 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 on page 8).

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

format.

Data in Window 0, Row 1 is reserved. DO NOT write to this location.

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.

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 21.

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 bit called ‘A’ allows you to distinguish the character

codes from the color codes corresponding to 1 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 boxes.

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-code attribute (bit A), or

when writing to a different I²C control register.

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