STV9937 datasheet(42/49 Pages) STMICROELECTRONICS

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Application Hints

STV9937

42/49

Application Hints

10.1

Software Hints

10.1.1 Programming Recommendations

1. Write a new allocation just before the RAM reset.

2. Write a new allocation at any time but take care of the window display.

3. When resetting the RAM and writing in it just after, write in the RAM respecting the same order

as the reset: from the first to the last reset window, from the first window address (row 0, col 0)

to the last, incrementing columns, then rows, then windows.

4. Define the window horizontal size prior to writing character and color codes in RAM.

HSWI is used to compute the RAM address.

10.1.2 Examples of Programming

It is recommended to program the STV9937 in the following sequence:

●

Via RGB Video mode

➺ set ENPB =1

➺ send data via RGB Video: Y then X coordinates.

●

Via I2C mode

➺ set ENPB =1, PBVM=1, PBON =0

➺ send data via I2C: X and Y coordinates.

➺ set PBON =1

●

Changing the mode

➺ set PBON = 0

➺ change PBVM bit

➺ write new coordinates, then the PBON can be set to 1.

Hard reset at power-up (following a power-up)

1. Write Window 0 registers to set the OSD parameters: write

➺ VCO[1:0], horizontal resolution and vertical height of characters,

➺ the position of reference,

➺ the allocations if they are incorrect

(by default: 320 characters for window 1, 128 characters for each of the others windows)

➺ the windows position and size,

➺ the color-boxes that will be used.

2. Write the character codes for each window to display.

3. Write the color-box data for each window to display.

4. Write the enable of windows: ENWi = 1 then ENOSD=1.

Change of position & size of 1 window (ex. window 3) without disable of window

1. Write new position and sizes.

2. Write new characters in the RAM.

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