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'LCD controller question...'
1999\04\27@212448 by spare

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Really quick question... I'm doing a PIC project which will require
interfacing to a Hitachi 44780 LCD controller. I know that the 'E'
signal is active high, but I'm hoping that the data is simply latched
on the *rising* edge, so that I can leave the 'E' line high when
the thing isn't in use. (This'll save me an inverter, 'cos I have a
bunch of convenient active low strobe signals for talking to
different peripherals).

Can anyone confirm that this is how it works?

Cheers,
Ben

1999\04\27@214133 by Jim Paul

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Ben,

All the literature I have shows 'E' being taken LOW after a write or read.
I can't say for certain what will happen if it is left high.  Try it and see
I guess.


Regards,


Jim
{Original Message removed}

1999\04\27@215201 by spare

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> Really quick question... I'm doing a PIC project which will require
> interfacing to a Hitachi 44780 LCD controller. I know that the 'E'
> signal is active high, but I'm hoping that the data is simply latched
> on the *rising* edge, so that I can leave the 'E' line high when
> the thing isn't in use. (This'll save me an inverter, 'cos I have a
> bunch of convenient active low strobe signals for talking to
> different peripherals).

Duh... thinking about it, or course it doesn't matter if the data
is latched on a falling or rising edge, provided that I know when it's
latched, and that it's ok to screw around with the data while the
E signal is high.

Any comments?

Cheers,
Ben

1999\04\27@220105 by Regulus Berdin

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Hi,

I looked a copy of an LCD FAQ, it is stated there the the data is
latched at the high to low edge of Enable.  So you can leave E high.

WRITE:

          ______ _____________________________ ___________
    RS  ______X_________valid_RS_level______X__________
              |                             |
              |                             |
              |<--tAS-->|        tAH-->|    |<--
        ______|         |              |    |____________
    R/W ______\_________|___R/W_low____|____/_____________
                        |              |
                        |<----PWEH---->|
                        |              |
                        |<-------------|-------TcycE----->|
                        |______________|                  |_________
    E   ________________/              \__________________/
                   tR-->||<--       -->||<--tF
                                       ||
                            |<--tDSW-->||
                            |        -->|   |<--tWH
          __________________|_______________|________________
    D0-D7 __________________X__valid_data___X____________


READ:
        ______ _____________________________ ___________
    RS  ______X_________valid_RS_level______X__________
              |                             |
              |                             |
              |<--tAS-->|        tAH-->|    |<--
        ______|_________|__   _    ____|____|____________
    R/W ______/         |  R/W high    |    \_____________
                        |              |
                        |<----PWEH---->|
                        |              |
                        |<-------------|-------TcycE----->|
                        |______________|                  |_________
    E   ________________/              \__________________/
                   tR-->||<--       -->||<--tF
                        |              ||
                 tDDr-->|   |<--       ||
                            |        -->|   |<--tRH
         ___________________|_______________|________________
    data ___________________X__valid_data___X____________


PWEH    Enable pulse width, high         450ns min
 Enable pulse must be at least 450 nanoseconds long, no maximum length

regards,
Reggie

--
e-mail: spam_OUTrberdinTakeThisOuTspambigfoot.com
ICQ#:   31651436
URL:    http://www.bigfoot.com/~rberdin


Ben Stragnell wrote:
{Quote hidden}

1999\04\27@224203 by Ben Stragnell

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Excellent - thanks!

I would have tried this out for myself, but I haven't ordered any
LCD's yet, and didn't want to unless I was confident my setup would
work.


Regulus Berdin wrote:
>
> Hi,
>
> I looked a copy of an LCD FAQ, it is stated there the the data is
> latched at the high to low edge of Enable.  So you can leave E high.

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1999\04\28@211214 by Myke Predko

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Hi Folks.

That's interesting to see about the data being latched on the downward
edge - I'll have to update my web page to note that.

And speaking up the web page, I spent a couple of hours tonight and added
some information about moving the cursor on the LCD as well as some
information on user-defined characters.  I will be adding a few more example
applications in the next few days.  Please take a look and let me know what
you think:

http://www.myke.com/engres/lcd.htm

As well, I've been doing a weekly survey on incredibly unimportant things -
this week it is asking "What was the best American fighter of World War II".
If you think the P-51 was overrated (or think that it should be recognized
as the best) - add your two cents on my home page:

http://www.myke.com

myke

{Original Message removed}

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