Sorry, I am not familiar with ACU75xx hardware. Possibly some other ports need to be set to enable CE function.
You can try downloading the ACU75xx firmware on s1fw.com, disassemble a BREC from one, then look at address 3000 for the code which displays hourglass. It will set the ports to select appropriate CE for the display.
More information at
http://wiki.s1mp3.org/