CXA1782CQ/CR
Commands
The input data to operate this IC is configured as 8-bit data; however, below, this input data is represented by
2-digit hexadecimal numerals in the form $XX, where X is a hexadecimal numeral between 0 and F.
Commands for the CXA1782 can be broadly divided into four groups ranging in value from $0X to $3X.
1. $0X (“FZC” at SENS pin (Pin 24))
These commands are related to focus servo control.
The bit configuration is as shown below.
D7
0
D6
0
D5
0
D4
0
D3
D2
D1
D0
FS4
DEFECT
FS2
FS1
Four focus-servo related switches exist: FS1, FS2, FS4, and DEFECT corresponding to D0 to D3, respectively.
$00 When FS1 = 0, Pin 8 is charged to (22µA – 11µA) × 50kΩ = 0.55V.
If, in addition, FS2 = 0, this voltage is no longer transferred, and the output at Pin 6 becomes 0V.
$02 From the state described above, the only FS2 becomes 1. When this occurs, a negative signal is output
to Pin 6. This voltage level is obtained by equation 1 below.
resistance between Pins 6 and 7
(22µA – 11µA) × 50kΩ ×
....
Equation 1
50kΩ
$03 From the state described above, FS1 becomes 1, and a current source of +22µA is split off.
Then, a CR charge/discharge circuit is formed, and the voltage at Pin 8 decreases with the time as
shown in Fig. 1 below.
0V
Fig. 1. Voltage at Pin 8 when FS1 gose from 0 → 1
This time constant is obtained with the 50kΩ resistance and an external capacitor.
By alternating the commands between $02 and $03, the focus search voltage can be constructed. (Fig. 2)
0V
$
00 02
03
02
03
02
00
Fig. 2. Constructing the search voltage by alternating between $02 and $03. (Voltage at Pin 6)
$04 When the fact that the RF signal is missing is detected and the scratches on the disc are detected with
DEFECT = 0, DFCT (FS3) is turned ON.
– 22 –
ETC [ ETC ]
