Problem with LC7981 resp. HD61830 with 6800 parallel interface

[Horstxxx]

I'm using U8G2 successfully with SSD1306 and SH1106 with I2C interface and also with KS0108 with parallel interface at Arduino Uno/Nano or ESP32 Dev. Module.

Furthermore, I have some 240 * 128 LM238 modules based on HD61830, which is (shall be) compatible with LC7981. Because of the number of pins needed for the module and the amount of RAM needed for the display content I use the ESP32.

Unfortunately I only get some random lines but not the expected image oder text on the display.

As the procedure is nearly the same for KS0108 with 8 Bit parallel interface, which is working, I think that my hardware setup is ok and I expect a problem in the software. This could be the timing or the pauses between the accesses to the interface.

The datasheet states, that the busy flag of the controller shall be checked before writing new data. As the interface is only written (read/write is fixed to write) this can`t be done by U8G2. Instead of checking the busy flag, we have to wait for an amount of time which is big enough so that the action before has completed.

Is this time great enough?
Where do I find it to change it for testing?

Some more ideas what I can check?

I could send such an display for testing (and present afterwards) if this would help to solve the problem.

Regards Horst Mayer