UPD16488AP datasheet(49/91 Pages) NEC

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Data Sheet S15745EJ2V0DS

µµµµPD16488A

5.8

Display Modes

5.8.1 Partial display mode

The

µPD16488A includes a function for outputting a display that uses only part of the LCD panel. The duty setting for

partial display mode can be selected as 1/12, 1/25, or 1/38. Parts of the LCD panel that are outside of the specified display

area are scanned with non-select waveforms. The partial start line address register (R21) is used to select which part of

the LCD panel to use for the partial display. The display area starts from the start line address and includes the number of

lines (12, 25, or 38 lines) that has been specified via the partial display mode setting (R10).

When entering this mode, the booster is set to the boost level number that has been set via the power system control

register 3 (partial display boost register) (R34) and the display start line is fixed as 00H. In addition, the bias level is

automatically changed to the value that has been set via the partial display mode setting (R10). The relationship between

the oscillator's frequency and the frame frequency in partial mode is also automatically changed.

Figure 5-24 shows the mutual relationship between the partial line start address and the LCD display.

When using the partial display mode, the blinking and reverse display functions can be used in the same way as during

full-dot display mode.

Caution The LCD driver voltage is lower in partial display mode, because the duty is lower than in normal display

mode. There may be restrictions on the usable duty depending on the LCD panel characteristics.

We recommend determining the partial duty after making a thorough evaluation of the actual LCD panel.

Figure 5-24. Relationship Between Partial Line Start Address and LCD Display

(in Partial Display Mode)

00H

01H

02H

03H

1DH

1EH

1FH

...

Display start line

(00H)

Partial display

start line

Non-display areas

Caution In partial display mode, the display start line setting register (R12) command is ignored.

When switching from normal display mode to partial display mode or from partial display mode to normal display mode, if

an electric charge remains in the smoothing capacitor that is connected between the LCD drive voltage pins (VLCD, VLC1 to

VLC4) and the VSS pin, troubles such as a brief all-black display may occur during the mode switching operation. To avoid

such troubles, we recommend using the following power-on sequence.

UPD16488AP Datasheet(PDF) 49 Page - NEC