HD44780 LCD controller organization
INDUSTRIAL LCD DISPLAYS / IGBT MODULES DISTRIBUTOR

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HD44780 LCD controller organization

Posted Date: 2024-02-03

The panel size that the HD44780 itself can control is 8 columns by 2 rows. To control larger LCD panels up to 40 columns, one or more segment extension driver chips, HD44100 or compatible chips are required, as shown in Figure 2a. It can also support various panel organizations described below.

16 columns 1 row

Typically this is configured by 1-line driver mode (only using half of the COM lines) and segment extension drivers. To eliminate the segment extension driver, it can also be configured based on 8 by 2 mode by placing the second row to the right of the row, as shown in Figure 2b. Therefore, 1-row drive mode is not used except for 8×1 panels.

20 columns 4 rows

The 4-line panel is configured by placing the right half of the character below the left half, as shown in Figure 2c. The rows on DDRAM are divided into rows and third rows on the LCD panel, and the second row on DDRAM are divided into rows two and four on the LCD panel.

40 columns 4 rows

This is a configuration using two HD44780s. The upper/lower parts of the LCD panel are controlled by an HD44780 respectively. The host interface signals, RS, R/W and DB[7:0]are connected to the same pins of the interface connector, only the E signal is connected separately.

cursor line

The bottom line of each line serves as the underline cursor. In some modules, this line is separated from the character body on the LCD panel shown in Figure 2d, so user characters using the underline may not appear.

11 line mode

This is one of the LCD driver modes that uses COM1 to COM10 as one line and does not use COM12 to COM16. In this mode, characters are 10 lines high and can represent numbers such as g, j, p, q, and y. However, two-row mode cannot be used in this configuration, so 11-row mode is not used in the universal CLCD module.


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