User`s manual

8: REGISTERS
S1D13504 SERIES HARDWARE FUNCTIONAL EPSON 1-83
SPECIFICATION (X19A-A-002-17)
8.2.8 Look-Up Table Registers
The S1D13504 has three internal 16 position, 4-bit wide Look-Up Tables. The 4-bit value pro-
grammed into each table position determines the color weighting of display data; the output gray
shade is derived from the Green Look-Up Table. These tables are bypassed in 15/16-bpp mode.
These three 16 position Look-Up Tables can be arranged in many different configurations to accom-
modate all the gray shade / color display modes.
bits 5–4 RGB Index Bits [1:0]
These bits are also used to provide access to the three internal Look-Up Tables (RGB).
A write to this register with RGB Index bits = 00 selected will position the internal
pointer to the Red LUT. Each read/write access to the LUT data will increment the
counter to point to the next LUT in order (R to G to B to R...). A read/write access to the
Blue LUT will also automatically increment the LUT address by 1. This provides an effi-
cient method for sequential writing of RGB data.
When the RGB Index bits = 01, 10, or 11, the internal pointer always points to the respec-
tive R, G, or B LUT. A read/write access to the LUT data will increment the LUT address
by 1.
bits 3–0 LUT Address Bits [3:0]
These 4 bits provide a pointer into the 16 position Look-Up Table currently selected for
CPU read/write access.
The Look-Up Table configuration (e.g. 1/2/4 banks) does not affect the read/write access
from the CPU as all 16 positions can be accessed sequentially.
bits 3–0 LUT Data Bits [3:0]
These 4 bits are the gray shade/color values used for display data output. They are pro-
grammed into the 4-bit Look-Up Table positions pointed to by LUT Address bits [3:0]
and RGB Index bits [1:0] (if in color display modes).
For example: in a 16-level gray shade display mode, a data value of 0001b (4 bits-per-
pixel) will point to Look-Up Table position one and display the 4-bit gray shade corre-
sponding to the value programmed into that location.
Look-Up Table Address Register
REG[24h] RW
n/a n/a
RGB Index
Bit 1
RGB Index
Bit 0
LUT Address
Bit 3
LUT Address
Bit 2
LUT Address
Bit 1
LUT Address
Bit 0
Table 8-15 RGB Index Selection
RGB Index Bits [1:0] Look-Up Table Access Pointer Sequence
00 Auto-Increment R, G, B LUT R[n], G[n], B[n], R[n+1], G[n+1] . . .
01 Auto-Increment Red LUT only R[n], R[n+1], R[n+2] . . .
10 Auto-Increment Green LUT only G[n], G[n+1], G[n+2] . . .
11 Auto-Increment Blue LUT only B[n], B[n+1], B[n+2] . . .
Look-Up Table Data Register
REG[26h] RW
n/a n/a n/a n/a
LUT Data
Bit 3
LUT Data
Bit 2
LUT Data
Bit 1
LUT Data
Bit 0