HMP8117_07 Datasheet, PDF (37/45 Pages) Intersil Corporation – NTSC/PAL Video Decoder

HMP8117
TABLE 62. PROGRAMMABLE FRACTIONAL GAIN
BIT
NO.
FUNCTION
SUB ADDRESS = 50_H
DESCRIPTION
RESET
STATE
7-6
Reserved
Set to 00_B for proper operation.
00_B
5
Select PFG Enable Set to “1” to enable the recommended PFG value in bits 4-0 below.
0_B
(Use 1_B)
4-0
PFG
Programmable Fractional Gain (PFG). When enabled by bit 5, changes the loop gain (response
time) of the AGC logic. Slower values provide some noise immunity to input signals with poor
sync/back-porch characteristics. Recommend using the slowest PFG value of 00001_B for
optimum performance. (Thus the recommended 8-bit register value = 21_H).
01100_B
(Use 01_H)
The 5-bit PFG value has a fractional representation as: 2⁰. 2^-1 2^-2 2^-3 2^-4
Sample PFG values:
00000_B: Gain = 0.0000 (freezes AGC at current value)
00001_B: Gain = 0.0625 (slowest AGC response time -- recommended PFG)
01100_B: Gain = 0.7500 (default)
10000_B: Gain = 1.0000
11111_B: Gain = 1.9375 (fastest AGC response time -- not recommended)
TABLE 63. MV STRIPE GATE
BIT
NO.
FUNCTION
SUB ADDRESS = 51_H
DESCRIPTION
RESET
STATE
7-6
Reserved
5-0
MV Stripe Gate
Set to 00_B for proper operation.
Defines the start of the gate for MV Color Stripe detection in 4xF_SC counts. The gate should start
prior to the chroma burst. Default value of 010100_B (14_H) is valid for NTSC. Recommend
100000_B (20_H) for PAL.
00_B
010100_B
TABLE 64. RESERVED
BIT
NO.
FUNCTION
SUB ADDRESS = 52_H
DESCRIPTION
RESET
STATE
7-0
Reserved
Set bit 5 to “1” for optimum performance.
02_H
(Use 22_H)
TABLE 65. AGC HYSTERESIS
BIT
NO.
FUNCTION
SUB ADDRESS = 53_H
DESCRIPTION
RESET
STATE
7-4
3-0
Reserved
Defines the amount of hysteresis in the AGC logic. Larger hysteresis values stabilize the AGC
with poor quality input signals. For example:
0000_B = No Hysteresis
1000_B = Default Hysteresis
1111_B = Maximum Hysteresis (Recommended hysteresis value)
Set to 0000_B for proper operation.
1000_B
(Use F0_H)
0000_B
TABLE 66. DEVICE REVISION
BIT
NO.
FUNCTION
SUB ADDRESS = 7F_H
DESCRIPTION
RESET
STATE
7-0
Device Revision
This 8-bit register specifies the device revision number. Data written to this read-only register is
01_H
ignored. The production baseline revision number is 01_H.
37
FN4643.3
April 19, 2007