Lucent Technologies MN10285K User Manual

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When the display lines are adjoined or overlapped, and the number of the above 

display code is extremely fewer than that of the below one, first line of the 
display line may not be output correctly.

In OSD circuit, font data to display are read from ROM and stored to the buffer. 
The data in the buffer are overwritten, after the present display code is output, to 

the display data of the next line.

Show the example when the display lines are adjoined. The number of the 

display code in the above line (line M) is reffered to n, and that of the below one 
(line M+1) is refferred N.

The buffer holds n display data of the last line of line M at the time of A (see 
figure below), and the data in the buffer are overwritten to the display data of the 

first line of line M+1 as time goes by. At the time of B the buffer holds n display 
data of the first line of line M+1.

In case n is smaller than N, N-n display data are needed to display the first line of 
line M+1, and to be written to the buffer before it is shown on the display.

Especially when n is extremely smaller than N, a large amount of the display data 
is needed to be written to the buffer before display. And in case writing is not 

done in time, it shows wrong data on the screen.

To prevent the wrong display written above, the first line of the below line is to 
be shown later enough after the last line of the above line is displayed.

The time (Td) needed for the correct display is caluculated as below.

Td = 0.8 + ( N - n ) 

×

 0.5 [µs]

n : the number of display code in the above line. (include HP, VP)
N: the number of display code in the below line. (include HP, VP)

n<N

 

 

HSYNC

display

Buffer

C

B

A