They are to put the display in 8 bit mode in case it is already in 4 bit
mode.

if it is in 4 bit mode you need to synchronize which half of the byte you
are sending, the only way to do this is to force it back into 8 bit mode and
then tell it to run 4 bit.  I have not had any problem with doing it this
way.

    cya,    Andrew...

----- Original Message -----
From: Robert A. LaBudde <ral@LCFLTD.COM>
To: <PICLIST@MITVMA.MIT.EDU>
Sent: Wednesday, November 24, 1999 1:10 PM
Subject: PIC control of LCD


> I have to admit I'm confused about how to interface to a Hitachi 44780
> controlled LCD via 4-bits.
>
> I've got a number of sample programs from books and websites, and there
> doesn't appear to be a unanimity on how to accomplish initialization of
the
> LCD.
>
> The most common initialization sequence is (after 15 ms startup delay):
>
> 1. Send 0x'3' (8-bit interface, 1/2 of command)
> 2. Wait > 4.1 ms
> 3. Send 0x'3'
> 4. Wait 100 us
> 5. Send 0x'3'
> 6. Wait 100 us
> 7. Send 0x'2' (4-bit interface)
> 8. Wait 40 us
> 9. Send 0x'28 (4-bit interface, 2-line)
> 10. Wait 40 us.
>
> When I try this sequence with my 20 x 4 display, it doesn't reliably
> initialize. So I went to the 44780 controller specification from the
> Hitachi website, and I found that they recommended the following sequence
> (after the 15 ms startup delay):
>
> 1. Send 0x'2'. (4-bit interface, 1/2 of command)
> 2. Wait 40 us.
> 3. Send 0x'28' (4-bit, 2-line)
> 4. Wait 40 us.
>
> This sequence initializes the LCD reliably. It also makes sense, since the
> 0x'2' command would be logically interpreted by the controller as a switch
> to 4-bit mode. Then the 0x'28' would be executed completely.
>
> My question is: What's with the extraneous three 0x'3' commands
recommended
> and used by others? Why are these even hypothetically necessary, since the
> controller comes up in 8-bit mode by default anyway?
>
>
>
>
> ================================================================
> Robert A. LaBudde, PhD, PAS, Dpl. ACAFS  e-mail: ral@lcfltd.com
> Least Cost Formulations, Ltd.                   URL: http://lcfltd.com/
> 824 Timberlake Drive                            Tel: 757-467-0954
> Virginia Beach, VA 23464-3239                   Fax: 757-467-2947
>
> "Vere scire est per causae scire"
> ================================================================
>