4- Vs. 8-bid LCD control

Hi all,

I’m playing with the serial LCD and I’m trying to figure the differences between the 4-bit & 8-bit control. What are the various advantages of these 2 modes?

Using 8bit mode means that it can transfer twice as many bits at once, meaning a faster frame rate on the LCD.

In practice the speed increase is insignificant for two reasons:-

1) The LCD library uses the digitalWrite() to output each individual bit. So using 8 bits one after the other is not much faster than doing four bits twice. 2) The time taken for the LCD to actually do anything with the data is very long compared with any slight speed increase in the data transfer.

The advantage of 4 bits is that you use fewer I/O pins. In general you should not need to use anything else.

I'm playing with the serial LCD and I'm trying to figure the differences between the 4-bit & 8-bit control

Why would a serial LCD need any more than 1 or 2 lines?

Sorry I missed the "serial" bit.

EDIT Which in the light of the later posts I was quite entitled to.

thanx for the fast reply.

I was thinking that the 8-bit interface would allow access to the LCD characters, such as these:http://wwwhomes.uni-bielefeld.de/achim/pc-e220/e220-lcd.gif

so there's no real advantage for using 8-bit?

If it's a parallel 4 or 8 bit LCD, you can still access the full character set. All the 4 bit mode does is to split each 8 bits into two lots of four bits. As pointed out, it makes the transfer slower, but the latency within the LCD controller will mean there is no perceptible difference

If it is a serial LCD, the question doesn't even apply.

my bad, it's a parallel LCD.

Thanx for clearing my doubts ;D

my bad, it's a parallel LCD.

In that case Mike's answer in reply #2 applies. In my opinion there is no real advantage to use the 8-bit interface when using a library written by someone else.

If you are interested in learning how to write your own code to control the LCD then starting out with the 8-bit interface is the way to go since it is simpler.