SPC8104 S-MOS Systems, SPC8104 Datasheet - Page 82

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

The VGA palette has been replaced by a 64x4 bit Gray Scale Lookup Table. This lookup table
operates in a similar manner as the VGA palette it replaces, with its registers at the same I/O
addresses. An Auxiliary Register control bit is provided to allow protecting the lookup table from
writes, if desired.
The LCD controller is designed to display a maximum of 16 absolute shades of grey on a LCD
rather than the 16 of 256k colors on a CRT monitor. Therefore a method of mapping colors origi-
nally intended for display on a 16/256 color CRT monitor onto a 16 gray LCD panel is required.
Hardware is provided to map the RGB (18 bit) values that are written to the lookup table by soft-
ware expecting to program a regular VGA palette. These RGB values are mapped using 1 of 2
selectable schemes into 4 bit gray scale values that are stored in the lookup table.
Details
This section gives a list of register bits in the SPC8104 that are different to the VGA standard.
Only differences are listed here; any bits not mentioned are the same as VGA. For a complete list
of the actual SPC8104 registers see section 11.3 on page 59
Clocking Mode Reg. (Index 01h)
Hardware Functional Specification
SP1-56
VGA palette replaced by reduced Gray Scale Lookup Table
Misc. Output Reg. (3C2h W, 3CCh R)
bit 1
bit 2,3
bits 6,7
Input Status Reg.0 (3C2h R)
bit 4
Input Status Reg.1 (3DAh R)
bits 1,2
bits 4,5
Feature Control Reg. (3DAh W, 3CAh R)
Sequencer Registers (3C4h,3C5h)
bit 0
bit 1
bit 2
S-MOS Systems, Inc. • Tel: [phone] • Fax: [phone] • http://www.smos.com
Enable DRAM
Read / write only. No other effect in hardware.
Clock Select
Read / write only. No other effect in hardware.
+/-Hsyn, Vsyn
Read / write only. No other effect in hardware.
Switch Sense bit
Deleted.
Light Pen
Read Only as 0,1.
Diagnostic
Deleted.
Register not supported.
8/9 Dot Clock
Read / write only. No other effect in hardware.
CPU Bandwidth
Read / write only. No other effect in hardware.
Shift-Load
Read / write only. No other effect in hardware.
X15-SP-001-08.1
412-1.0
SPC8104