Specifications

mikroElektronika | Free Online Book | PIC Microcontrollers | Appendix B: Examples
If there are no characters displayed or if all of them are dimmed when the display is switched on, the first thing that
should be done is to check the potentiometer for contrast adjustment. Is it properly adjusted? The same applies if the
mode of operation has been changed (writing in one or two lines).
LCD Memory
LCD display contains three memory blocks:
● DDRAM - Display Data RAM;
● CGRAM - Character Generator RAM; and
● CGROM - Character Generator ROM.
DDRAM Memory
DDRAM memory is used for storing characters that should be displayed. The size of this memory is sufficient for storing 80
characters. Some memory locations are directly connected to the characters on display.
It works quite simply: it is enough to configure the display to increment addresses automatically (shift right) and set the
starting address for the message that should be displayed (for example 00 hex).
After that, all characters sent through lines D0-D7 will be displayed as a message format we are used to- from left to
right. In this very case, displaying starts from the first field of the first line because the address is 00 hex. If more than 16
characters are sent then all of them will be memorized, but only the first sixteen characters will be visible. In order to
display the rest of them, a shift command should be used. Virtually, everything looks as if the LCD display is a window
which shifts left-right over memory locations containing different characters. In reality, this is how the effect of message
shifting on the screen has been created.
If the cursor is on, it appears at the location which is currently addressed. In other words, when a character appears at
the cursor position, it will automatically move to the next addressed location.
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