355
14.3 Structure of LCD Controller/Driver
Table 14.3-1 LCDC Control Register (LCR1) Bit Functions
Bit
Function
Bit 7
CSS:
Frame cycle
generation clock
selection bit
Selects the frame clock, which generates the frame cycle for
LCD display. "0" selects the output of the timebase timer
derived from the main clock divided by FCL2
7; "1" selects the
subclock as the frame clock.
Check:
The timebase timer output may not be selected as the frame
clock in the main-stop and subclock modes because the
main clock oscillator is stopped in those modes.
Note:
When the timebase timer output is selected, the frame clock
is not affected when clock speed is changed via the speed
shift function. (The timebase timer’s count clock is not
supplied through the speed shift function.)
Bit 6
LCEN:
Watch mode
operation enable
bit
Determines whether the LCD controller/driver will operate in
watch mode. If this bit is "1", the LCD display will continues to
operate after the system goes to watch mode; if it is "0", the
LCD will cease operation.
Check:
To use the display in watch mode, the subclock must be
selected as the frame clock (CSS = 1).
Bit 5
VSEL:
LCD drive supply
voltage control bit
In devices that have an internal divider resistor, the VSEL
bit controls the divider current path continuity. A "1" in this
bit completes the divider current path; a "0" opens it. This
bit must be "0" when external divider resistors are used.
Bit 4
BK:
Display blanking
selection bit
Blanks/unblanks the LCD.
Setting this bit to "1" (blank) outputs a "deselect" waveform to
the LCD segments (which blanks the display).
Bit 3
Bit 2
MS1, MS0:
Display mode
selection bits
Select one of three output waveform duty ratio modes. The
mode selected affects the common pins used. Setting both bits
to "0" turns "off" the display (stops LCD controller/driver display
operation).
Check:
Before going to a mode in which the selected frame cycle
generate clock oscillator is stopped (stop mode, etc.), these
bits should be written to "00B" to turn off the display.
Bit 1
Bit 0
FP1, FP0:
Frame cycle
selection bits
These bits select one of four LCD display frame cycles.
Check:
To determine this register setting, calculate the optimum
frame frequency for the LCD module you are using. Note
that the frame cycle is a function of main clock frequency.