20
Register and Bit De nitions (continued)
SC654
Main Fade Control (04h)
This register sets the fade status and rate for the main
backlight group.
Bits [D5:D2]
These bits are unused and are always zeros, so the
maximum pulse count for this register is 3.
MFADE1, MFADE0[D1:D0]
These bits are used to enable and set the rise/fall rate
between two backlight currents as follows in Table 7.
Table 7 — Main Display Fade Control Bits
MFADE1 MFADE0
Fade Feature Rise/Fall Rate
(ms/step)
0 0 OFF
01 8
10 16
11 32
The number of steps used to change the backlight current
will be equal to the change in binary count of bits
MBL[4:0].
When a new backlight current is set, the backlight current
will change from its current value to a new value set by
bits MBL[4:0] at the rate determined by MFADE1 and
MFADE0 bits. The total fade time is determined by the
number of steps between old and new backlight values,
in Table 4, multiplied by the rate of fade in ms/step.
Backlight Grouping Con guration (05h)
This register assigns the LEDs to the back light bank
con gurations.
Bits [D5:D3]
These bits are unused and are always zeros, so the
maximum pulse count for this register is 7.
MB2, MB1 and MB0 [D2:D0]
These bits are used to set the number of LED drivers dedi-
cated to each backlight group. This allows the device to
drive up to three different sets of LEDs with different
current settings. Note that any driver assigned to any LED
group can still be disabled independently if not needed.
The code set by these bits determines how the LED drivers
are assigned among the three LED groups according to
the assignments listed in Table 8. Default state for each of
these three bits is “0” (all LEDs assigned to main display).
Table 8 — Backlight Grouping Con guration
MB2 MB1 MB0
Main
Display
LED
Drivers
Sub
Display
LED
Drivers
Third
Display
LED
Drivers
0 0 0 BL1-BL6
0 0 1 BL1-BL3 BL4-BL6
0 1 0 BL1-BL2 BL3-BL4 BL5-BL6
011
BL1-BL2,
BL5-BL6
BL3 BL4
1 0 0 BL1-BL3 BL4-BL5 BL6
1 0 1 BL1-BL4 BL5 - BL6
1 1 X BL1-BL5 BL6
