ch7012a Chrontel, ch7012a Datasheet - Page 27

• Manufacturer Part Number: ch7012a
• Description: Ch7012 Tv Output Device
• Manufacturer: Chrontel

CHRONTEL
Vertical Position Register
Register VP is used to shift the displayed TV image in a vertical direction ( up or down) to achieve a vertically
centered image on screen. The entire bit field, VP[8:0], is comprised of this register HP[7:0] plus the MSB value
contained in the Text Enhancement register, bit VP8. The value represents the TV line number (relative to the VGA
vertical sync) used to initiate the generation and insertion of the TV vertical interval (i.e. the first sequence of
equalizing pulses). Increasing values delay the output of the TV vertical sync, causing the image position to move
up on the TV screen. Decreasing values, therefore, move the image position DOWN. Each increment moves the
image position by one TV lines (approximately 2 input lines). The maximum value that should be programmed
into the VP[8:0] value is the number of TV lines per field minus one half (262 or 312). When panning the image up,
the number should be increased until (TVLPF-1/2) is reached, the next step should be to reset the register to zero.
When panning the image down the screen, decrement the VP[8:0] value until the value zero is reached. The next
step should set the register to TVLPF-1/2, and then decrement for further changes.
Black Level Register
Register BL controls the black level. The luminance data is added to this black level, which must be set between 65 and
175. When the input data format is 0 through 3 or 5 the default values are 131 for NTSC and PAL-M with DAC Gain 21h
[2:1] = `00’, 109 for PAL with DAC Gain 21h [2:1] = `01’, and 102 for NTSC-J with DAC Gain 21h [2:1] = `01’. When
the input data format is 4, 6 or 7 the default values are 113 for NTSC and PAL-M with DAC Gain 21h [2:1] = `10’, 94 for
PAL with DAC Gain 21h [2:1] = `11’, and 88 for NTSC-J with DAC Gain 21h [2:1] = `11’.
Contrast Enhancement Register
Bits 2-0 of register CE control contrast enhancement feature of the CH7012, according to the figure below. A
setting of ‘0’ results in reduced contrast, a setting of ‘1’ leaves the image contrast unchanged, and values beyond ‘1’
result in increased contrast.
201-0000-042 Rev 2.1, 10/20/2004
DEFAULT:
DEFAULT:
DEFAULT:
SYMBOL:
SYMBOL:
SYMBOL:
TYPE:
TYPE:
TYPE:
BIT:
BIT:
BIT:
R/W
R/W
BL7
VP7
7
0
7
1
7
R/W
R/W
VP6
BL6
6
0
6
0
6
R/W
R/W
VP5
BL5
5
0
5
0
5
R/W
R/W
BL4
VP4
4
0
4
0
4
R/W
R/W
BL3
VP3
3
0
3
3
0
R/W
R/W
R/W
VP2
BL2
CE2
Symbol:
Address:
Bits:
Symbol:
Address:
Bits:
Symbol:
Address:
Bits:
2
0
2
0
2
0
R/W
R/W
R/W
BL1
CE1
VP1
CH7012A
1
1
1
1
1
0
VP
06h
8
BL
07h
8
CE
08h
3
R/W
R/W
R/W
BL0
CE0
VP0
27
0
0
0
1
0
1