Excellent site!  This led me to the following, which has PIC-specific
examples:

http://www.iaehv.nl/users/pouweha/lcd.htm

Thanks!

-Ed V.

At 12:22 PM 9/16/97 PST, you wrote:
>Ed, I don't have the answer for you, but I bet you can find it here:
>
>   http://www.paranoia.com/~filipg/HTML/LINK/F_Tech_LCD.html
>
>
>CIAO - Martin R. Green
>elimar@bigfoot.com
>
>----------
>From:   Ed VanderPloeg[SMTP:evanderploeg@CREO.COM]
>Sent:   Tuesday, September 16, 1997 2:29 PM
>To:     PICLIST@mitvma.mit.edu
>Subject:        [OT] LCD "busy" signal
>
>I'm trying to use a PIC to drive a standard, run-of-the-mill, LCD display,
>and am having trouble understanding the operation of the "busy flag".  The
>model is an Optrex DMC-20481 (or something like that) with an
>industry-standard Hitachi HD44780 controller.  Some important bits were
>lost in the manual's translation from Japanese, so I'm left a little
>confused.  After sending a command or data byte to the LCD I think you can
>do 1 of 2 things before sending the next:
>
>1. Wait a worst-case period of time before sending the next byte (not a
>problem).
>2. Read the "busy" flag before sending the next byte (problem).
>
>For efficiency I'm trying to wait for the busy signal as described in the
>databook but it's not working as expected.  Seems like the LCD is forever
>busy.
>
>First of all, this busy signal is intended for use as I've described above,
>yes?  (or is it a busy signal for the 4-bit interface mode only?)  Next,
>when reading a byte from the LCD the PIC is still in control of the
>"enable" signal, correct? (i.e. it's not driven by the LCD).  Here's my
>psuedo-code sequence for waiting for the LCD:
>
>1. Set TRIS register for LCD connection to input, control lines output.
>2. Set the "data/command" line to low to indicate a command
>3. Set the "read/write" to high to indicate a read
>4. Set "data ready" high, wait a NOP (16MHz clock) for the LCD to spit out
>the byte
>5. Read in the LCD data byte to W
>6. Pull the "data ready" signal low again
>7. AND W with 0x80 (busy flag is bit 7)
>8. If zero, it's not busy and we can continue, otherwise wait and read busy
>flag again.
>
>But this seems to hang and think the LCD is forever busy.  Ideas?
>
>-Ed V.
>
>