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STV9432

100MHz OSD FOR MONITOR

STMicroelectronics 

STV9432

7 - SOFTWARE RESET REGISTER

403F

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RST

To perform a software I2C reset of the device, set the RST bit to ONE.

This bit will be automatically reset by the device.

Software Reset will put all Write registers at their default power-on value, and reset all internal logic

blocks except the I2C bus interface itself. It will not change the RAM contents.

SELXTAL

This bit must be set to ONE in order to operate the oscillator in the external crystal

mode.

In its ZERO default state, this bit enables the internal RC mode oscillator.

8 - ON-SCREEN DISPLAY

The STV9432 on-screen display is able to display

any line of characters (character strip) anywhere

in the screen.

Character strings are programmed by the MCU in

RAM via I2C bus. Character shapes are coded in

the internal ROM font. Character strips may be

adjacent or separated by vertical spaces (Spacing

strips).

Consequently, one display page is made of a list

of Character strips and Spacing strips.

A Top Margin and a Left Margin are programmable

in dedicated registers.

8.1 - RAM PROGRAMMING

Each Strip is associated with a 2 bytes Strip

Descriptor.

There are two Strip Descriptors:

- The Character Strip Descriptors containing the

Text string Ram address of the Character Strip,

- The Spacing Strip Descriptors which specify the

vertical space height.

In the example shown in Figure 4 on page 8, the

OSD screen, is made of 9 strips.

In RAM, there is:

- one list of 9 Strip descriptors

(size = 9 x 2 bytes = 18 bytes),

- 6 Text strings, each of them made of the character

codes from the line of text.

8.1.1 - Two kinds of Data:

Strip Descriptors and Character Codes

An OSD screen is made of a number of Character

and Spacing strips.

Text strings can be programmed anywhere in

RAM. The Descriptor list can be located at 16 dif-

ferent addresses in RAM. The address is defined

in the Display Control Register. It is consequently

possible to store up to 16 different pages in RAM.

Two groups of Data make one OSD screen:

- a Strip Descriptors list,

- Text strings - one per Character strip.

The current Displayed page is specified in the Dis-

play Control Register. It refers to a given Page

Descriptor list.

Figure 4. Display Page: List of Character and Spacing strips

TOP MARGIN

Text line number one

Text line number two

Text line number three

Text line number four

Text line number five

Text line number six

Strip 1 : Character Strip

Strip 2 : Character Strip

Strip 3 : Spacing Strip

Strip 4 : Character Strip

Strip 5 : Spacing Strip

Strip 6 : Character Strip

Strip 7 : Character Strip

Strip 8 : Character Strip

Strip 9 : Spacing Strip (Bottom Margin)

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