VT1621M VIA, VT1621M Datasheet - Page 32

• Manufacturer Part Number: VT1621M
• Description: TV Encoder
• Manufacturer: VIA

Color Bar Test Pattern Generator
The VT1621 and VT1621M all have a built-in color test
pattern generator that produces 75% amplitude and 100%
saturation EIA colors for NTSC and PAL video standards as
illustrated in Figure 13 through Figure 18.
Subcarrier Generation
This device uses a 32-bit-word to synthesize the subcarrier.
The value of the sub-carrier increment required to generate the
desired subcarrier frequency is found with the following
equations:
NTSC: FSCI[31:0] = 2
PAL:
The 32-bit Sub-Carrier Value, FSCI, is defined in Rx16-19.
H_Total is the number of output pixels desired per line. F
the encoder clock frequency if Rx5[4]=0 (FSCI Auto Adjust
Disabled);
Adjust Enabled). This allows the generation of any desired
subcarrier for any desired video standard.
subcarrier increment FSCI[31:0] must be loaded by the serial
interface before the subcarrier can be enabled. In order to
prevent any residual errors from accumulating, the subcarrier
is reset every two lines for the NTSC standard and every field
for the PAL standard.
Burst Generation
Subcarrier burst generation is a function of the video standard
(e.g. NTSC or PAL), the subcarrier frequency increment
(FSCI), and the burst horizontal begin and end register
settings.
horizontal sync to prevent invalid sync pulses from being
generated. The burst blanking is automatically controlled by
Revision 1.0 June 17, 2002
-or-
-or-
Mode
FSCI[31:0] = (int) (2
FSCI[31:0] = 2
FSCI[31:0] = (int) (2
25*
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10
11
12
16
17
18
21
22
23
2
3
6
7
The burst will automatically be blanked during
F
clk
=14.31818MHz if Rx5[4]=1 (FSCI Auto
Rx00
[7-5]
000
000
001
001
010
010
010
011
011
011
100
100
100
101
32
32
* [455 / (2 * H_Total)]
* [(1135/4 + 1/625) / (H_Total)]
Rx04
[1-0]
10
10
10
10
10
10
10
10
10
10
10
10
10
10
32
32
* 3.579545 / F
* 4.43361875 / F
Rx02
[5-3]
010
000
010
000
010
000
100
000
100
011
011
001
101
000
Table 5. Display Modes for PAL (M)
Input Format
clk
512 x 384
512 x 384
720 x 400
720 x 400
640 x 400
640 x 400
640 x 400
640 x 480
640 x 480
640 x 480
800 x 600
800 x 600
800 x 600
720 x 480
)
clk
)
The 32-bit
clk
is
H_Total * V_Total
- 27-
1040 x 630
1040 x 700
1064 x 750
800 x 420
784 x 525
945 x 420
936 x 525
840 x 420
840 x 525
840 x 600
784 x 525
784 x 600
800 x 630
858 x 525
the selected video format. The burst rise and fall times can be
configured by programming the chip registers.
Power Down mode
The VT1621 and VT1621M can be powered down by
programming their registers.
maintained when the TV Encoder chip is in power down
mode .
Macrovision Anti-Copy Protection
The VT1621M features Macrovision 7.1 anti-copy protection.
This algorithm modifies the NTSC/PAL signals to inhibit
recording on VCR devices, while not affecting direct TV
viewing.
protection block are fully programmable.
Display Modes
There are a total of 27 display modes.
determined by four factors: Input resolution, TV standard, TV
lines, and Scaling Ratio. Both VT1621 and VT1621M are
designed to accept input resolutions of 640x480, 800x600,
640x400 (including 320x200 scan-doubled output), 720x400,
and 512x384. The VT1621 and VT1621 are also designed to
support output to either NTSC or PAL television standards.
The VT1621 and VT1621M all provide interpolated scaling
with selectable ratios of 1:1, 3:4, 5:4, 5:6, 7:8 and 7:10 in
order to support adjustable overscan or underscan operation
when displayed on TV. These combinations of ratios result in
a matrix of useful operating modes. PAL-M has 525 lines just
like NTSC but the horizontal frequency and the frame rate are
different from NTSC. Therefore, PAL-M and NTSC share the
same modes but the pixel clock frequency varies. All the
modes are listed in Table 5 and Table 6 below.
All of the parameters that control the anti-copy
Pixel Clock
VT1621 / VT1621M TV Encoder
20.160020
24.696025
23.814024
29.484029
21.168021
26.460026
30.240030
24.696025
28.224028
30.240030
39.312039
43.680044
47.880049
13.513514
Standard
PAL(M)
PAL(M)
PAL(M)
PAL(M)
PAL(M)
PAL(M)
PAL(M)
PAL(M)
PAL(M)
PAL(M)
PAL(M)
PAL(M)
PAL(M)
PAL(M)
All register contents are
Output
Functional Descriptions
Scaling
Each mode is
7/10
5/4
1/1
5/4
1/1
5/4
1/1
7/8
1/1
7/8
5/6
5/6
3/4
1/1