| Q1: |
What is OSD? |
| A1: |
OSD is designed for monitor applications to display built-in fonts onto a monitor screen. The display operation occurs by transferring data and controls information from the micro controller to the OSD through a serial data interface. |
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| Q2: |
Why is window 2 or window 3 unable to display while window 1 is displaying? |
| A2: |
For OSD having three windows: window 1 has the highest priority and window 3 has the least. For OSD having four windows, window 1 has the highest priority and window 4 has the least when two windows are overlapping. |
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| Q3: |
What are the user fonts of OSD? |
| A3: |
User fonts are programmable fonts. Each user font consists of 12¡Ñ18 dot matrix. Users can program user fonts by software. |
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| Q4: |
When I use the double width character function, some characters cannot be displayed onto the monitor screen. Why is that? |
| A4: |
If the double width character function is chosen, only even column characters can be displayed onto a monitor screen and the odd column characters will be hidden. |
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| Q5: |
When I initiate the OSD, some registers cannot be programmed. Why? |
| A5: |
When PLL is unstable, do not write data in any registers except the registers of HORR and Vco. It is necessary to wait for the PLL to become stable while: (1) the HORR register; (2) the (Vco1, Vco0) bits; (3) the horizontal signal (HFLB), is/are being changed. |
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| Q6: |
How do I access the display RAM ADDRESS register, namely the ATTRIBUTE register and CONTROL register? |
| A6: |
Use the writing transmission format (c) for example:
Format (c) : S-R-C-D-D-D¡K
, where S = Slave address (7A), R = Row address, C = Column address, D = Display data
Access ADDRESS register: Row address value bit7, bit6, bit5 must be 1, 0, 0.
Access ATTRIBUTE register: Row address value bit7, bit6, bit5 must be 1, 0, 1.
CONTROL register is at Row 15 and Row 16, writing method is the same as access ADDRESS register.
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| Q7: |
How do I reset the OSD by software? |
| A7: |
First write 0xA0 to Row 15, Column 31.
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| Q8: |
How do I calculate the Pixel clock of OSD PLL? |
| A8: |
Pixel clock = HFLB Freq * HORR * 12
, where HFLB is pin 5 input H-Sync Frequency,
HORR is control register at Row 15 and Column 15, and its value must be greater than or equal to 36.
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| Q9: |
How do I show OSD font address larger than 255? |
| A9: |
To represent 512 font we need 9 bit address D8 D7 D6 D5 D4 D3 D2 D1 D0,
use format (c) for example S-R-C-D-D¡K
D = D7-D0,
D8 is at C (Column address) bit 5.
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| Q10: |
How do I read 14 byte auto sizing measurement data of OSD? |
| A10: |
Use following OSD read format:
S-D-D-D-D-D-D-D-D-D-D-D-D-D-D-dummy D-dummy D¡K
, where S=Slave address : 7B, D = auto sizing measurement dataafter sending 14 byte data OSD will continue send dummy data until stop condition occurrs.
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| Q11: |
What do I do if the OSD has jitters? |
| A11: |
The problem can be solved by inverting the OSD clock (reg A1 D6). |
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