NHD‐3.5‐320240MF‐ATXL#‐CTP‐1 Problem with standby mode

[guenter]

Hello,

we have a low power application and need to run the display 'NHD‐3.5‐320240MF‐ATXL#‐CTP‐1' in standby mode.
For a test setup we connect all lines, except the RGB data lines to a Microchip evaluation board.
We use no pull-up or pull-down resistors on any line. The LED (anode/cathode) is powered by a extra power supply (18VDC).
The serial communication is ok, we can run the test pattern mode and read register values back.
We have tested two display revisions:
- old revision of the 'NHD‐3.5‐320240MF‐ATXL#‐CTP‐1', with the display driver NT39016D and touch controller FT5206
- newer revision of the 'NHD‐3.5‐320240MF‐ATXL#‐CTP‐1', with the display driver NV3035C and touch controller FT5216

With the old revision (display driver NT39016D) the display can be setup in standby mode (current <30ľA)
The newer revision (display driver NV3035C) the standby current is about 1-2mA.
We use the same hardware and same source code. After power-up, a microcontroller performs a display hardware reset (RSTB line) and then writes the appropriate value to the register R00.
For sleep mode the value 0x01,  for test pattern mode the value 0xFF.

We also noticed that for the new display revision we have to toggle the CLKIN (dot clock signal) twice after writing to the register to start the test pattern.
We read the register value back and see that it is written with the correct value, but the test pattern mode is not starting without toggling the clock line.
With the old display this is not necessary.

What is the difference between the two display revisions?
How to get the new display in standby mode?

Any suggestions?