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Initialization Issues

HD44780 based LCD displays MUST be initialized .This is done in two ways. One is by internal reset circuit and the other is by using commands.The white text below is an extract from a Hitachi document.

Initializing by Internal Reset Circuit
An internal reset circuit automatically initializes the HD44780U when the power is turned on. The
following instructions are executed during the initialization. The busy flag (BF) is kept in the busy state
until the initialization ends (BF = 1). The busy state lasts for 10 ms after VCC rises to 4.5 V.

  1. Display clear
  2. Function set:
    DL = 1; 8-bit interface data
    N = 0; 1-line display
    F = 0; 5 ´ 8 dot character font
  3. Display on/off control:
    D = 0; Display off
    C = 0; Cursor off
    B = 0; Blinking off
  4. Entry mode set:
    I/D = 1; Increment by 1
    S = 0; No shift

Sounds good ? Now read this :

Note: If the electrical characteristics conditions listed under the table Power Supply Conditions Using
Internal Reset Circuit are not met, the internal reset circuit will not operate normally and will fail
to initialize the HD44780U. For such a case, initialization must be performed by Instruction.

And see this:

Yes,initializing by the internal reset circuit is easy , and really works.So,Why on earth should one use the initialization by instruction method ? Read the yellow text above once more if you wish. Initialization by internal reset circuit depends on your power supply. If you do not want your software to be power supply dependent you may want to use the initialization by instruction method.It is shown below.