CL-PS7500FE
System-on-a-Chip for Internet Appliance
Table 12-5. Deriving High-Speed 2-bit Cursor Data from the Normal 8-bit Output — CD[1:0]
CD[1]
CD[0]
ED[1]
ED[0]
0
0
1
1
0
1
0
1
BPD[1]
BPD[0]
0
BPD[1]
1
0
BPD[0]
1
12.5 Liquid Crystal Displays
The CL-PS7500FE can drive single-panel LCDs at 1-, 2-, 4-, 8-, 16-, or 32-bpp and dual-panel LCDs at
1-, 2-, or 4-bpp. Grayscaling is provided at up to 16 shades. The CL-PS7500FE can also drive single-
panel color LCDs with no grayscaling in the Normal (video) mode. Two bits control LCD operation:
●
lcd (EREG[13]): configures the external data port ED[7:0] for LCD operation and enables the grayscaling
logic (EREG[1:0] must be set to ‘0x01’)
●
dup (CONREG[13]): enables Duplex mode and should be set for dual-panel LCDs.
12.5.1 LCD Grayscaling
To obtain a grayscaled output from the CL-PS7500FE, EREG[13] must be set. This configures the Exter-
nal port for LCD operation. Disable the DACs to save power since the CL-PS7500FE cannot simulta-
neously drive both CRT and LCD displays.To obtain this data out of the ED[7:0] port, EREG[1:0] must be
set to value ‘0x01’.
The CL-PS7500FE provides a grayscaling algorithm that modulates the data output. Grayscaling is pos-
sible at 1-, 2-, or 4-bpp. The data is output from the device as one or two 4-bit quantities, depending on
whether single- or dual-panel LCDs are used, at one quarter the pixel rate. The lower 4 bits of the Green
LUT control the upper panel (ED[7:4]) and the 4 bits of the Ext LUT control the lower panel (ED[3:0]).The
palette can still provide a mapping of logical-to-physical color.The cursor palette is similar, though the pro-
gramming of the cursor position needs special treatment (refer to Appendix B). If a single-panel LCD is
used, use ED[7:4] and program the Green LUT accordingly (ED[3:0] held low in this mode).The grayscal-
ing logic lies between the output of the video MUX and the external port and works as described below.
There are effectively 16 physical gray levels available and, in 1-, 2-, or 4-bpp mode, the palettes are pro-
grammed to give a mapping of the logical color-to-physical shade. The resultant 4-bit pixel value out of
the video MUX is modulated according to its value, the raster number, and the point on the raster where
it is generated. The result is a single bit that is, on average, high for a time equal to the actual 4-bit value.
For a single-panel screen, four of these bits are collected together and output as a nibble at one quarter
the pixel rate on ED[7:4]. ED[4] represents the fourth pixel; and ED[7] represents the first pixel.
If Duplex mode is selected, the pixel stream for the upper half-screen is obtained from the Green LUT;
that for the lower half-screen is obtained from the Ext LUT. Both pixel streams are simultaneously passed
through the grayscale logic and output as two nibbles on ED[7:4] (upper half-screen) and ED[3:0] (lower
half-screen).
12.5.2 Dual-Panel LCDs (Duplex Mode)
Duplex mode is configured by setting CONREg[13] and EREG[13]. The screen parameters are set
according to the requirements of the LCD panel.
June 1997
129
ADVANCE DATA BOOK v2.0
VIDEO FEATURES
CIRRUS [ CIRRUS LOGIC ]
