hd66420 Renesas Electronics Corporation., hd66420 Datasheet - Page 30

• Manufacturer Part Number: hd66420
• Description: Ram-provided 160 Channel 4-level Grey Scale Driver For Dot Matrix Graphics Lcd
• Manufacturer: Renesas Electronics Corporation.

HD66420
Partial Display Function
The HD66420 can display only a part of a full display. The bias ratio of this partial display is 1/4 from V
to GND, the duty ratio is 1/8 and rest of display is scanned with unselected levels. 8 levels of contrast can
be selected wit data bit 2 to 0 of R16. The position of this partial display can be located at any position with
using partial display position register. To launch this mode, following processes are needed:
(1) supplied voltage to VLCD must be cut off, PWR bit can be used if external voltage supplier is
(2) set DTY0, 1 bits (R1)
(3) set COM scanning direction (ADC bit)
(4) set display position (R11, R5)
(5) set contrast level (R16 data-bit 2 to 0)
The clock frequency may be 180kHz at normal display mode. When a partial display is driven, oscillation
frequency will be 18kHz, 1/10 of that of normal display mode. This function is useful for lower power
dissipation. To change clock frequency, follow the process which is showed in Figure 21.
Warning: VLCD must be cut off when partial display mode is launched. Vcc is supplied to LCD
driving circuit instead of VLCD. So if VLCD is supplied externally during partial display mode, Vcc
short-circuit to VLCD.
Table 6 Partial Display Block
R11
H’00
H’01
H’02
H’03
H’04
H’05
H’06
H’07
H’08
H’09
30
controlled with DCON output (R0)
ADC = 1
COM1
COM9
COM17
COM25
COM33
COM80
COM72
COM64
COM56
COM48
COM8
COM16
COM24
COM32
COM40
COM73
COM65
COM57
COM49
COM41
ADC = 0
COM8
COM16
COM24
COM32
COM40
COM73
COM65
COM57
COM49
COM41
COM1
COM9
COM17
COM25
COM33
COM80
COM72
COM64
COM56
COM48
CC