44780 LCD - Why would I use 8 data lines?

[andywpg]

I am working on my first LCD project. Its a 4 X 16 44780 controlled LCD.

In the PBP manual for LCDOUT, two schematics are presented. One uses four data lines, the other eight. What I don't understand is why I would use eight when it appears I can use four.

BTW, I am using a 16F886, if that makes any difference.

Would someone be so kind as to explain this to me? I have searched the forum, but can't seem to find anything on this, and the PBP manual doesn't explain why either.

Thanks,

Andy

[andywpg]

I am working on my first LCD project. Its a 4 X 16 44780 controlled LCD.


Sorry, I meant 4 X 20 character

[Demon]

I'm curious also. The closest I could google for an explanation was:
http://www.cornerstonerobotics.org/curriculum/lessons_year2/erii14_lcd1.pdf


p. 2
This 4-bit mode is beneficial when using a
microcontroller, as fewer input/output lines are required.

I'm guessing there was an evolution of hardware involved. The parallel LCDs were most likely first used by devices that used 8 bits (1 byte) - I'm going to guess discrete components. Then microcontrollers came along and were smart enough to be able to use only 4 lines.

From everything I've seen so far, it's a personal choice. I used 8 before, but I'm now starting to use 4 because my projects become more complex and pin usage becomes more important.

Robert
:)

[mister_e]

It's just faster, but in 99.999% of the application you don't need it that fast.

[aratti]

Theoreticaly it should be twice as fast, since with the 8 lines you send one byte while with 4 lines you have to send two nibbles.

Al.