ML6461CS View Datasheet(PDF) - Micro Linear Corporation

Part Name

Description

Manufacturer

ML6461CS

CCIR656 NTSC Video Encoder

Micro Linear Corporation 

ML6461

FUNCTIONAL DESCRIPTION (Continued)

smoothing) is done to the beginning and end of the active

portion of the line. When this bit is set (B24=1), the

ML6461 is optimized for "analog" line encoding, where

the number of active pixels is 712 for CCIR656 rates and

640 for square pixel rates. The beginning and end of the

active video portion of the line is tapered (smoothed) to

minimize ringing introduced due to fast transitions. Figure

14 below illustrates the timing comparisons.

Note: For the square pixel rate the only difference

between "analog" and "digital" encoding is the tapering

(smoothing) at the beginning and end of the active video

portion of the line. The number of pixels encoded during

the active video portion is the same in both cases. The

positioning of the active portion is the same as in "analog"

line encoding.

ANALOG_HRESET, B23 This bit is active only in

external slave mode and when the external sync is given

at the beginning of active video. In this mode,

ANALOG_HRESET (B23) must be used in conjunction

with ANALOG_HBLANK (B23) to choose between

"analog" and digital" line encoding. The possible

approaches are summarized in Table 4 below.

FULL_BAR, B22 This bit is used to program the ML6461

to encode in normal modes or 100% amplitude video

(100% color bar). When this bit is set (B22=1), the

ML6461 is ready to handle 100% color bars. With 75%

amplitude signals, this bit should be cleared (B22=0) for

optimum signal to noise performance.

JAPAN_BLANK, B21 This bit is used to program the

ML6461 to encode Japanese NTSC by removing the 7.5

IRE setup in blanking and thus boosting the gain of luma

and chroma DACs. This bit is set (B21=1) to handle

Japanese NTSC modes.

WIDE_VBLANK, B20 Determines which lines to blank

at the beginning of each field. For wide blanking, this bit

is set (B20=1), the ML6461 provides 15 lines of blanking.

For narrow blanking, this bit is cleared (B20=0), the

ML6461 provides 9 lines of blanking.

CC_21, B19 This bit enables (B19=1) and disables

(B19=0) the transmission of closed captioning data on

line 21.

1.56µs

5.3µs

9 CYCLES

4.7µs

9µs

9µs + 4 PIXELS

CCIR656 DIGITAL LINE ENCODING: 720 PIXELS, 1440 TCLKs

CCIR656 ANALOG LINE ENCODING: 712 PIXELS, 1424 TCLKs

SQUARE PIXEL ANALOG AND

DIGITAL ENCODING: 640 PIXELS, 1280 TCLKs

Figure 14. Timing of Horizontal Blanking Interval and Active Video

ANALOG_

HRESET

B23

ANALOG_

HBLANK

B24

RECOMMENDED

ENCODING

TIME BETWEEN

H_SYNC AND

ACTIVE VIDEO

PIXELS

ENCODED

CCIR 656 SQUARE PIXEL

0

0

ITU-R656

9µs

Digital TV Line

720

640

0

1

Optional

9µs + 4pixels

712

640

= 9.3µs

See Note 1

1

0

Not

Recommended

1

1

ITU-R/SMPTE

9µs + 4pixels

712

640

Analog

= 9.3µs

See Note 2

Note 1: Ignore first four and last four pixels.

Note 2: Ignore last eight pixels.

Table 4. Video Encoding Standards and Horizontal/Active Video Timing

EDGE

SMOOTHING

(B24 = 1)

none

Yes

Yes

20

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