AK8855 Datasheet, PDF (61/81 Pages) Asahi Kasei Microsystems – NTSC/PAL Digital Video Decoder

[ASAHI KASEI]
AK8855
Notification Function of Internal Conditions
The AK8855 has Status Register ( R/W ) [ Sub Address 0x10 ] to notify externally the AK8855 internal
condition.
Bit allocation of Status Register is as follows.
Sub Address 0x10
bit 7
bit 6
bit 5
bit 4
bit 3
bit 2
bit 1
bit 0
VBWSSDE
T
EXTDET
CCDET
AGCSTS CPLLLCK PKWHITE COLKILST
NSIG
(1) No Signal Decision
The AK8855 makes a decision of no signal input condition. When it is decided to be no input signal, data output
becomes Black level output ( Y = 0x10, Cr / Cb = 0x80 ).
Its result is notified to outside by output pin NSIG and [ NSIG ]-bit of Status Register.
Output Logical State is as follows.
Signal condition
[NOSIG]-bit
NSIG pin
With signal input
0
0
No signal input
1
1
(2) COLKILST
This is to indicate that Color Killer Function has been activated as Color signal level is very small.
[COLKIL]-bit
Input level
Condition
0
Normal signal
1
Color Killer is enabled
(3) Input Level Overflow Notification Function
This function is activated when the decoded result of Luminance signal exceeds 255.
[ PKWHITE ]-bit
“1” is set to this bit when an overflow of Luminance signal is detected.
When [ PKWHITE ]-bit becomes “1”, an overflow occurred at Luminance signal processing path.
[PKWHITE]- bit
Input level
Condition
0
Input signal overflow occurred
1
No input overflow occurred
(4) Color PLL Status
This is to indicate PLL Lock condition with input Color Burst signal.
[ CPLLLCK ]-bit
[CPLLLCK]-bit
Input level
0
It is locked with input Color Burst signal
1
It is not locked with input Color Burst signal
Condition
(5) AGC Status
This is to indicate status of adaptive AGC
[ AGCSTS ]-bit
[AGCSTS]-bit
Input level
0
Operation in Sync AGC
1
Operation in Peak AGC
Condition
MS0319-E-03
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