SPT2210SCT 查看數據表（PDF） - Signal Processing Technologies
零件编号
产品描述 (功能)
生产厂家
SPT2210SCT Datasheet PDF : 22 Pages
| |||
COLOR LOOKUP TABLE (CLUT)
DESCRIPTION
CLUT FORMAT AND DATA LIMITS
The CLUT has 16 entries and is set up in YCrCb three-
byte format. (See below.) The upper 6 bits in the Y data
are used (lower two are filled with zero) and the upper 5
bits in the Cr/Cb data are used (lower 3 bits are filled with
zero). Therefore the setting ranges are Y = 00H to FCH
(midpoint value = 80H) and Cr and Cb = 00H to F8H (mid-
point value = 80H).
The numerical values of Cr and Cb are expressed in off-
set binary form, irrespective of the setting of bit D3 in
Command Register 2. Since no limit processing is carried
out in connection with the CLUT data entries, it is neces-
sary to set Y within the limits of 16 to 236 (10H to ECH)
and Cr/Cb within the limits of 16 to 240 (10H to F0H).
Bit composition of Y (address=10H~1FH)
D7 D6 D5 D4 D3 D2 0 0 1st Byte
MSB
LSB
Bit composition of Cr (offset binary, address=10H~1FH)
D7 D6 D5 D4 D3 0 0 0 2nd Byte
MSB
LSB
Bit composition of Cb (offset binary, address=10H~1FH)
D7 D6 D5 D4 D3 0 0 0 3rd Byte
MSB
LSB
TRANSPARENT COLOR
Transparent colors can be used in chroma key mode
(See Combining Video and Graphics Signals for more
details.) Transparent colors can be entered in the CLUT
with the following data values for Y, Cr and Cb:
Y = 00H, Cr = 80H, Cb = 80H
When these data values are selected in the CLUT, the
graphics data becomes transparent and the SPT2210
displays the video YD7...0 and CD7...0 data instead.
COLOR SPACE CONVERSION FROM RGB TO
YCRCB FOR CLUT ENTRY
The SPT2210 CLUT stores data in YCrCb format only.
RGB graphics data must be converted in the host before
loading the CLUT. The conversion for RGB to YCrCb is
shown here:
Y = 0.2990 x R + 0.5770 x G + 0.1140 x B
Cr = 0.5000 x R – 0.4187 x G – 0.0813 x B +128
Cb = 0.1684 x R – 0.3316 x G + 0.5000 x B + 128
Example: Assume that each RGB data is 8 bits in length
and that their values are R = 120, G = 96, B = 96. The
values of Y, Cr and Cb are given by the following calcula-
tions:
Y = 0.2990 x 120 + 0.5770 x 96 + 0.1140 x 96 = 102
Cr = 0.5000 x 120 – 0.4187 x 96 – 0.0813 x 96 +128
= 140
Cb = 0.1684 x 120 – 0.3316 x 96 + 0.5000 x 96 + 128
= 124
Since the SPT2210 CLUT only uses the upper 6 bits in
the Y data and the upper 5 bits in the Cr/Cb data, it is
necessary to round the results above. The second bit is
rounded in the Y calculation and the third bit is rounded in
the Cr and Cb calculation. The results are shown below:
Y = 102 = 01100110 (binary) results in 01101000
(binary) = 104
Cr = 140 = 10001100 (offset binary) results in
10010000 (offset binary) = 144
Cb = 124 = 01111100 (offset binary) results in
10000000 (offset binary) = 128
ACCESSING THE COLOR LOOKUP TABLE
The method for accessing the CLUT is different from the
method for accessing the command registers because
each entry of the CLUT has a length of 3 bytes at each
address. The CLUT is accessed by means of three suc-
cessive bytes after writing the address. Note that Y, Cr
and Cb cannot be accessed individually in the CLUT.
They must be accessed in units of three bytes sequen-
tially.
Color Lookup-table Register Read and Write
Operation
Address Setup:
Set CS_, RS low.
Set the data bus to the address required (10H – 1FH),
then set WR_ low.
Set WR_ high, then CS_ and RS high.
This completes the address write and points to the CLUT
registers that may be read from or written to.
Register Read:
After completing address setup, Set CS_ low, RS
high.
Set RD_ low; this enables the data from the pointed-
to register onto the data bus (first byte, Y data).
Set RD_ high, then set RD_ low; this enables the data
from the pointed-to register onto the data bus (second
byte, Cr data).
Set RD_ high, then set RD_ low; this enables the data
from the pointed-to register onto the data bus (third
byte, Cb data).
Set RD_, CS_ and RS high.
This completes the three-byte sequence of CLUT register
read operation at the specified address.
SPT
SPT2210
15
8/22/00
Share Link: 