HD44780U Datasheet, PDF (10/59 Pages) Hitachi Semiconductor – Dot Matrix Liquid Crystal Display Controller/Driver

HD44780U
Display Data RAM (DDRAM)
Display data RAM (DDRAM) stores display data represented in 8-bit character codes. Its extended
capacity is 80 × 8 bits, or 80 characters. The area in display data RAM (DDRAM) that is not used for
display can be used as general data RAM. See Figure 1 for the relationships between DDRAM addresses
and positions on the liquid crystal display.
The DDRAM address (A_DD) is set in the address counter (AC) as hexadecimal.
• 1-line display (N = 0) (Figure 2)
 When there are fewer than 80 display characters, the display begins at the head position. For
example, if using only the HD44780, 8 characters are displayed. See Figure 3.
When the display shift operation is performed, the DDRAM address shifts. See Figure 3.
High order
bits
Low order
bits
AC
(hexadecimal) ^{AC6 AC5 AC4 AC3 AC2 AC1 AC0}
Example: DDRAM address 4E
100 11 10
Figure 1 DDRAM Address
Display position
(digit)
12 3
DDRAM
address
00 01 02
(hexadecimal)
45
03 04 ^{. . . . . . . . . . . . . . . . . .}
79 80
4E 4F
Figure 2 1-Line Display
Display
position 1 2 3 4 5 6 7 8
DDRAM _{00 01 02 03 04 05 06 07}
address
For
shift left
01 02 03 04 05 06 07 08
For
shift right ^{4F 00 01 02 03 04 05 06}
Figure 3 1-Line by 8-Character Display Example
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