hd66717 Renesas Electronics Corporation., hd66717 Datasheet - Page 49

• Manufacturer Part Number: hd66717
• Description: Low-power Dot-matrix Liquid Crystal Display Controller/driver -
• Manufacturer: Renesas Electronics Corporation.

Oscillator Circuit
The HD66717 can either be supplied with operating clock pulses externally (external clock mode) or
oscillate using an internal R-C oscillator and an external oscillator-resistor (internal oscillation mode), as
shown in Figure 28. An appropriate oscillator-resistor must be used to obtain the optimum clock
frequency according to the number of display lines (Table 18). Instruction execution times change in
proportion to the operating clock frequency or R-C oscillation frequency; MPU data transfer rate must be
appropriately adjusted (see Table 17, Instruction List). Figure 29 shows a sample LCD drive output
waveform, where 4-lines are displayed with 1/34 multiplexing duty ratio.
Table 19
Item
Multiplexing duty ratio
Oscillator resistance (R
CR oscillator frequency
Frame frequency
Oscillation Frequency and LCD Frame Frequency
1) When an external clock is used
Clock
f
)
V
OSC1
CC
HD66717
= 3V
Figure 28 Oscillator Circuit
1-Line Display
NL1, NL0 = 00
620 k
40 kHz
67 Hz
1/10
2) When an internal oscillator is used
Rf
OSC1
OSC2
HD66717
2-Line Display
NL1, NL0 = 01
1/18
300 k
85 kHz
79 Hz
The oscillator frequency can be
adjusted by oscillator resistance
(Rf). If Rf is increased or power
supply voltage is decreased, the
oscillator frequency decreases.
77 Hz
3-Line Display
NL1, NL0 = 10
1/26
200 k
120 kHz
4-Line Display
NL1, NL0 = 11
1/34
150 k
160 kHz
78Hz
HD66717
501