I think I finally found some relevant information about this display here:
http://www.lcdwiki.com/3.97inch_16BIT_Module_OTM8009A_SKU:MRB3971
with a link to a schematics (of an older variant of the display board):
http://www.lcdwiki.com/res/MRB3971/3.97inch_MRB3971_Schematic.pdf
This schematics shows that I was wrong about the IMx jumpers. My first test was with the wrong jumper changed, and the later test most likely was with short circuit of the 3.3V logic voltage.
So I once more need to try to change soldering these tiny jumpers, hopefully with more luck!
Jean-Marc
No luck, not successful.
It should be possible to use 16bit commands, 16bit "addresses" for OTM8009A, by sending the low byte as parameter of the ADRSFT (Address Shift Function) and then the high byte as 8bit command.
ADRSFT first needs to be enabled, with a known sequence of 8bit command and 8bit parameters.
But I get no reaction on the display.
And I always get zero when reading registers with 8bit address and IF set for 8 bit.