DDP3310B Datasheet, PDF (8/60 Pages) Micronas – Display and Deflection Processor

DDP 3310B
ADVANCE INFORMATION
2.1.5. Soft Limiter
The dynamic range of the processed luma signal must
be limited to prevent the CRT from overload. An appro-
priate headroom for contrast, peaking, and brightness
can be adjusted by the TV manufacturer according to
the CRT characteristics. All signals above this limit will
be “soft”-clipped. A characteristic diagram of the soft
limiter is shown in Fig. 2–3. The total limiter consists of
three parts:
Part A includes adjustable tilt point and gain. The gain
before the tilt value is 1. Above the tilt value, a part
(0…15/16) of the input signal is subtracted from the
input signal itself. Therefore, the gain is adjustable
from 16/16 to 1/16, when the slope value varies from 0
to 15. The tilt value can be adjusted from 0 to 511.
Part B has the same characteristics as part A. The
subtracting part is also relative to the input signal, so
the total differential gain will become negative if the
sum of slope A and slope B is greater than 16 and the
input signal is above the both tilt values (see character-
istics).
Finally, the output signal of the soft limiter will be
clipped by a hard limiter adjustable from 256 to 511.
2.1.6. Chroma Input
The chroma input signal can either be YC_rC_b in 4:1:1
or in 4:2:2 format. For the digital signal processing, the
time-multiplexed chroma samples will be demulti-
plexed and synchronized with the signal at the HS pin.
The input formatter accepts either two’s complement
or binary offset code. Also, the delay can be adjusted
within a range of ±2 input clocks relative to the luma
signal; this doesn’t affect the chroma multiplex.
Table 2–2: 4:1:1 Chroma format
Pin Name
Pixel Number
1
2
3
4
C7
C_b17 C_b15 C_b13
C6
C_b16 C_b14 C_b12
C5
C_r17
C_r15
C_r13
C4
C_r16
C_r14
C_r12
Note: C_xy; x = pixel number, y = bit number
C_b11
C_b10
C_r11
C_r10
Table 2–3: 4:2:2 Chroma format
Pin Name
Pixel Number
1
2
3
4
C7
C_b17
C_r17
C_b37
C6
C_b16
C_r16
C_b36
C5
C_b15
C_r15
C_b35
C4
C_b14
C_r14
C_b34
C3
C_b13
C_r13
C_b33
C2
C_b12
C_r12
C_b32
C1
C_b11
C_r11
C_b31
C0
C_b10
C_r10
C_b30
Note: C_xy; x = pixel number, y = bit number
C_r37
C_r36
C_r35
C_r34
C_r33
C_r32
C_r31
C_r30
Output
511
400
300
200
100
Part A
Part B
Slope A [0...15]
0
2
4
6
8
10
12
14
Tilt A [ 0...511]
Tilt B [0...511]
Hard limiter
0
Calculation example for the soft-
limiter input amplitude.
2
4
6
8
Y Input
16...235 (ITU-R 601)
10
Range= 256...511 ^{Black Level 16 (constant)}
12
Contrast
63
14
Dig. Brightness 20
Slope B [0...15]
Peaking
off
Limiter input signal:
(Yin-black level)× CTM/32‘+BRM
(235-16)×63/32 + 20 = 451
0
0
100
200
300 400 500 600
700 800
900
Limiter Input
1023
Fig. 2–3: Characteristics of soft limiter A and B and hard limiter
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