LCD display Busy Flag

Not a direct answer to your question, but I found it easier to just ignore the busy flag, and use a timer to wait for the display. That way you can have the CPU do something useful instead of wasting time waiting for the display.

Using a timer also simplifies the code (no need to toggle I/O direction bits), and you won't need the R/W signal, saving an I/O pin.

You guys have not hit any display freeze problems yet. Remember th controller is a micro and can also go "nuts" for any of the reasons tha any micro can. If you treat this as a write only memory, you hav absolutley no indication whether your data is being written to the displa or not. Using the busy bit provides you with a little more confidence tha the system is working. If the display fails to go ready within pre-determined time period, you can try to reset the display throug software by re-initializing, and failing that (provided you have enoug foresight to include it in the hardware design), by cycling the power t the display since it does not have a reset line.

-Aubrey

That's a good point. I haven't had problems yet, but some LCD display hardware may be more vulnerable than others. The display I'm using for my next project does have a real reset line, so I'll connect the R/W line just in case. For maximum efficiency, the timer interrupt can check the busy bit only every screen refresh, rather than for every character.

Hi,

I need to use a 4x20 lcd but it's my first time to use suce a device. Ca you suggest any online material that I can read so that I can implement th LCD display on my project? I'm using a zilog mcu and I have enough pins fo all the pins of the lcd. Thanks!

"sani_figs" wrote in news:d5qdnStUtIhSlxLVnZ2dnUVZ snipped-for-privacy@giganews.com:

You have to read the datasheet of the lcd controller.

Bye Jack

And be advised that the Busy flag is not operative until the controller is initialized. Time delays have to be used until initialization is complete.

What Zilog part are you using? Z8? Z80? eZ80?

I just saw some wonderful replies to your earlier query leading to the Optrix page with data and examples:

There are many piggyback/daughterboards for LCDs that convert them to RS232/serial, so they're easier to use. Many of them publish the schematic and software and detailed "gotchas" of the interface. Dale Wheat's "PIC-an-LCD" A Character-Based Serial LCD Controller was published in Circuit Cellar Inc. Issue #206 September 2007