There are two Enables because there are two controller chips on that type of display. Each controller has only RAM type storage for 80 bytes of character codes. A 4x40 display has 160 character positions so you can see why two controllers are used.

It would not be useful to try to connect the two E's together because both display controllers would try to respond to your software at the same time.

The easiest way to figure out what the offsets into the display RAM are for each position on the actual display is to fill each controllers display memory up with an 80 byte pattern and then observe the result on the screen. In this case you could do one of the controllers at a time. I have sometimes loaded a string like this into the sequential DDRAM addresses: "A123456789B123456789C123456789D123456789E123456789F123456789G123456789H123456789"

When something like this is displayed it is a piece of cake to correlate the DDRAM addresses to the character positions on the glass.

Michael Karas