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Function Of Pca And Pma Area; Opc And Ropc - LG GWA-4164B Service Manual

Dvd/cd rewritable drive
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8. Function of PCA and PMA area

1) PCA (Power Calibration Area)
• PCA area is used to determine the correct Laser Power for a disc.
– Method 1 : PCA area is divided by a track.
– Method 2 : The previous Calibration value is referred.
– Method 3 : ROPC is used to determine Laser Power value automatically in data writing.
• CD-R Disc can write maximum 99 Tracks but CD-RW Disc can write unlimited tracks because it has a rewritable
function.
2) PMA (Program Memory Area)
• It has a track information (track No, track Start/End time) of every track before writing completed.
– PMA area has the last written point and the next writable point of a disc.
– In case of CD to CD copy, some writer may not write PMA area.
* When Disc is Finalized,
PMA information is transferred to the Lead_In area so that general Driver can read it.
* Because PCA and PMA area exist before Lead-In area, General CD Player or CD-ROM Drive can't read
these areas.

9. OPC and ROPC

1) OPC (Optimum Power Control)
• This is the first step of writing process, because CD writer has its own laser power value and media have different
writing characteristics,
– This is determined by the Writing characteristic, speed, temperature, and humidity.
– Laser wavelength is determined by the environmental temperature (775~795nm) and Optical Laser Power is
determined by the test and retry.
• Asymmetry and optimum writing Power
– EFM signal Asymmetry is determined by the writing power.
Therefore, Optical Power which has the same value to the preset power value can be estimated by measuring
HF signal Asymmetry on the PCA area.
• Measurement of Asymmetry
* Parameter setting (Beta) : Using AC coupled HF signal before equalization
Beta = (A1+A2)/(A1-A2)
A1
0
A2
30
P << Po
Time
P = Po
Time
P >> Po
Time

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