SPC8104 S-MOS Systems, SPC8104 Datasheet - Page 102

• Manufacturer Part Number: SPC8104
• Description: VGA LCD CONTROLLER
• Manufacturer: S-MOS Systems

The data written to the LCD Lookup Table Data Register varies depending on the setting of the
Green-only/NTSC Weighting Select bit (AUX[01] bit 4) which selects either a Green-only or an
approximated NTSC gray scale weighting scheme:
The data read from the LCD Lookup Table Data Register always returns a 6-bit data value of
which bits 5-2 are the 4-bit gray scale value and bits 1 and 0 are images of bits 5 and 4 (the same
as). All three Red, Green, and Blue read accesses return the same value.
Hardware Functional Specification
LCD Lookup Table Data Register
3C9h RW
n/a
1st access (“Red”)
n/a
2nd access (“Green”)
n/a
3rd access (“Blue”)
n/a
1st access (“Red”)
n/a
2nd access (“Green”)
n/a
3rd access (“Blue”)
n/a
SP1-76
GS NTSC Weighting Writes (AUX[01] bit 4 = 0)
GS Green-Only Weighting Writes (AUX[01] bit 4 = 1)
S-MOS Systems, Inc. • Tel: [phone] • Fax: [phone] • http://www.smos.com
approx. NTSC Weighting:GS = [5R + 9G + 2B] / 16
Green-only Weighting: GS = G
(see below)
n/a
n/a
n/a
n/a
n/a
n/a
n/a
Note that a write to the Lookup Table Data Registers may only occur if the 3C9h Write Disable bit
(bit 4 in Auxiliary Register 00) is set to 0, otherwise the write to the Data Registers will not have an
effect. Writes to the Read Address or Write Address registers themselves are not affected by the
3C9 Write Disable bit.
bit 5
bit 5
bit 5
bit 5
bit 5
n/a
n/a
bit 4
bit 4
bit 4
bit 4
n/a
bit 4
n/a
5
X15-SP-001-08.1
G
4
G
Gray Scale Lookup Table Data
bit 3
bit 3
bit 3
bit 3
n/a
bit 3
n/a
3
Green Component Data
Green Component Data
G
Blue Component Data
Red Component Data
2
G
1
G
0
bit 2
bit 2
bit 2
bit 2
n/a
bit 2
n/a
bit 1
bit 1
bit 1
bit 1
n/a
bit 1
n/a
bit 0
bit 0
bit 0
bit 0
n/a
bit 0
n/a
412-1.0
SPC8104