Hi
As far as I know, SBN1661 is compatible to the SED1520. For the SBN1661 you can use the two CS lines to latch data into the controller. RW can be fixed (to GND i think), but you need to set RS (also named DI or A0) to 0 or 1, depending if you want to send data or instructions. Both (cmds and data) are required for proper programming of the device.
I had once added support to u8glib (http://code.google.com/p/u8glib/wiki/device) for the SBN1661, so it should also work for SED1520. U8glib low level access is here: Google Code Archive - Long-term storage for Google Code Project Hosting.
Oliver