HD66421 Datasheet, PDF(30/46 Page) Hitachi Semiconductor – (RAM-Provided 160 Channel 4-Level Grey Scale Driver for Dot Matrix Graphics LCD)

English

English German Russian Spanish Italian Polish Chinese Japanese Korean French Portuguese	Language :

HD66421 Datasheet, PDF (30/46 Pages) Hitachi Semiconductor – (RAM-Provided 160 Channel 4-Level Grey Scale Driver for Dot Matrix Graphics LCD)

◁

Preliminary

Rev. 1.1E '99.02.10

HD66421

Power Down Modes

The HD66421 has a standby function providing

low power-dissipation, which is initiated by

internal register settings. During standby mode,

all the HD66421 functions are inactive and data

in the display RAM and internal registers except

the DISP bit are retained. However, only control

registers can be accessed during standby mode.

HD66421 has an another power down mode:

partial display. In this mode only a part of display

is active. However, this duty ratio is 1/8 so the

external power supply for LCD drive will be

inactive. The oscillator does not halt, thus

dissipating more power than standby mode. Table

6 lists the LCD driver output pin status during

standby mode. Figure 27 shows the procedure for

initiating and canceling a standby mode and

figure 28 shows the procedure for changing

oscillator. Note that these procedure must be

strictly followed to protect data in the display

RAM.

Table 7 Output Pin Status during Power Down modes

Signal Name

COM1-COM100

SEG1-SEG160

STBY

Status

Output VLCD (display off)

Output common signals (VLCD - GND)

Output VLCD (display off)

Output segment signals (VLCD - GND)

Set STBY bit to 1 and AMP bit to 0

(control register 1)

Standby mode

Clear STBY and PWR bits to 0 and AMP bit to 1

(control register 1)

Oscillation halts

OP amp power off

External power supply off

Initiation

Oscillator starts

OP amp power on

Internal operation starts

Wait for oscillation and external

power supply to stabilize

Cancellation

Set DISP bit to 1 (control register 1)

Display starts

Figure 27 Procedure for Initiation and Canceling a Standby Mode

Set HOLT bit to 1 (control register 1)

Set DTY or GRAY bit to 1 (control register 2)

Wait for oscillation to stabilize

Clear HOLT bit to 0 (control register 1)

Internal operation stops

Oscillator 2 starts working

Internal operation starts

Figure 28 Procedure for Changing Oscillator

▷