HD66766R Datasheet, PDF (68/97 Pages) Hitachi Semiconductor – 132 x 176-dot Graphics LCD Controller/Driver for 65K Colors

HD66766R
Rev. 1.0-1 / September 2002
Frame-Frequency Adjustment Function
The HD66766R has an on-chip frame-frequency adjustment function. The frame frequency can be
adjusted by the instruction setting (DIV, RTN) during the LCD drive as the oscillation frequency is
always the same. When the display duty is changed, the frame frequency can be adjusted to be the same.
If the oscillation frequency is set to high, an animation or a static image can be displayed in suitable ways
by changing the frame frequency. When a static image is displayed, the frame frequency can be set low
and the low-power consumption mode can be entered. When high-speed screen switching, for an
animated display, etc. is required, the frame frequency can be set high.
Relationship between LCD Drive Duty and Frame Frequency
The relationship between the LCD drive duty and the frame frequency is calculated by the following
expression. The frame frequency can be adjusted in the retrace-line period bit (RTN) and in the
operation clock division bit (DIV) by the instruction.
(Formula for the frame frequency)
Frame frequency =
fosc
[Hz]
Clock cycles per raster-row × division ratio × 1/duty cycle
fosc: R-C oscillation frequency
Duty: drive duty (NL bit)
Clock cycles per raster-row: (RTN + 26) clock cycles
Division ratio: DIV bit
Example Calculation 1 Setting the maximum frame frequency to 60 Hz
Display duty: 1/176
Retrace-line period: 0 clock (RTN3-0 = “0000”)
Operation clock division ratio: 1 division
fosc = 60 Hz × (0 + 26) clock × 1 division × 176 lines = 275 (kHz)
In this case, the R-C oscillation frequency becomes 275 kHz. The external resistance value of the R-C
oscillator must be adjusted to be 275 kHz. The display duty can be changed by the partial display, etc. and
the frame frequency can be the same by setting the RNT bit and DIV bit to achieve the following.
(Partial display): Display duty: 1/40
Retrace-line period: 1 clock (RTN3-0 = “0002”)
Operation clock division ratio: 3 division
Frame frequency = 275 kHz/ ((3 + 26) clock × 4 division × 40 lines) = 59.2 (Hz)
Example Calculation 2 Switching the frame frequency to suit animation/static image display
(Animation display): Frame frequency: 90 Hz
Display duty: 1/176
Retrace-line period: 0 clock (RTN3-0 = “0000”)
Operation clock division ratio: 1 division
fosc = 90 Hz × (0 + 26) clock × 1 division × 176 lines = 412 (kHz)
(Static image display): Frame frequency: 90 Hz
Display duty: 1/176
Retrace-line period: 1 clock (RTN3-0 = “1101”)
Operation clock division ratio: 1 division
Frame frequency: 412 kHz/ ((13 + 26) clock × 1 division × 176 lines) = 60.0 (Hz)
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