HD44780U Datasheet, PDF (39/59 Pages) Hitachi Semiconductor – Dot Matrix Liquid Crystal Display Controller/Driver

HD44780U
Instruction and Display Correspondence
• 8-bit operation, 8-digit × 1-line display with internal reset
Refer to Table 11 for an example of an 8-digit × 1-line display in 8-bit operation. The HD44780U
functions must be set by the function set instruction prior to the display. Since the display data RAM
can store data for 80 characters, as explained before, the RAM can be used for displays such as for
advertising when combined with the display shift operation.
Since the display shift operation changes only the display position with DDRAM contents unchanged,
the first display data entered into DDRAM can be output when the return home operation is performed.
• 4-bit operation, 8-digit × 1-line display with internal reset
The program must set all functions prior to the 4-bit operation (Table 12). When the power is turned on,
8-bit operation is automatically selected and the first write is performed as an 8-bit operation. Since
DB0 to DB3 are not connected, a rewrite is then required. However, since one operation is completed in
two accesses for 4-bit operation, a rewrite is needed to set the functions (see Table 12). Thus, DB4 to
DB7 of the function set instruction is written twice.
• 8-bit operation, 8-digit × 2-line display
For a 2-line display, the cursor automatically moves from the first to the second line after the 40th digit
of the first line has been written. Thus, if there are only 8 characters in the first line, the DDRAM
address must be again set after the 8th character is completed. (See Table 13.) Note that the display shift
operation is performed for the first and second lines. In the example of Table 13, the display shift is
performed when the cursor is on the second line. However, if the shift operation is performed when the
cursor is on the first line, both the first and second lines move together. If the shift is repeated, the
display of the second line will not move to the first line. The same display will only shift within its own
line for the number of times the shift is repeated.
Note: When using the internal reset, the electrical characteristics in the Power Supply Conditions Using
Internal Reset Circuit table must be satisfied. If not, the HD44780U must be initialized by
instructions. See the section, Initializing by Instruction.
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