jhd162a 1602 LCD - Enable (E) pin - understanding of it

Hi folks!

I'm currently using this common type of 1602 display successfully with arduino, but just wanted to ask the experts here about the Enable (E) pin. Or to check my understanding of how it works.

According to guides, when the E pin is 'high', the LCD module does not capture (grab) the data from its register lines (such as the data register lines or the command register lines), right?

The LCD module only captures (grabs) the data presented at its register lines only when the E pin "transitions" from high to low, right? (ie. negative-going edge transitions triggers data-taking).

Is the duration of time when the E-pin is LOW important? That is, does the E-pin need to go LOW for some minimum amount of time?

And if the E-pin does go LOW for some minimum amount of time, then is there also a maximum amount of time that it is allowed to stay low?

And one more question is...... once the LCD module has taken (captured) - then is the LCD module still 'active' (processing) when we make the E-pin go high? That is, making the E-pin go high doesn't put the LCD module into an idle mode right?

Thanks for any help in advance!

Hi.

Those guides you consulted, do they include the HD44780 datasheet ?

The information that you are requesting can be found in the datasheet mentioned in the previous post. Specifically you should look at "Figure 26 Read Operation" on page 58 which must be used along with the "Bus Timing Characteristics" on page 49.

A simplified version of these diagrams can be found here.

The LCD module only captures (grabs) the data presented at its register lines only when the E pin "transitions" from high to low, right? (ie. negative-going edge transitions triggers data-taking).

Your interpretation is correct.

There is no maximum limit on the amount of time that the various signals can be driven high or low. You can successfully run this display using manually operated switches without a microprocessor as was demonstrated in a magazine article a few decades ago. A document based on that article can be found here.

Don

Hi Don and Mas3!

Thanks very much for your time and your help with this. Don - thanks for guiding me to those details. I'll be writing that down in my notes.

I always didn't quite understand what was happening below the surface with that Enable-pin, as in I incorrectly thought that the E-pin going high would just disable all processing activity in the module.

Thanks for putting me on the right path Don. Thanks for adding the link to that document. I'll hang onto that document as well. Genuinely appreciated. The simplified diagram is excellent. Genuinely appreciated Don.

Mas.... I looked at that excellent documentation that you linked before. I had seen that document, but didn't fully understand it all. But now that I'm on the right path, I'll study that document more. Thanks for adding that link too!

Kenny