You must be blind because the IC is practicaly made of digital I/O ports.
Some of the possibilities for interface are:
S1, S2, S3 in conjunction with K1, K2, K3, K4 (the 4 K port addresses are for digital interface, they must be specified by a seperate pin to control data direction.)
SA0-SA12 these are used for the external memory address, but you could design the system to go through microcontroller to get to the external memory, this would allow you to share data with the microcontroller if needed.
I would go with the S1-S3 and K1-K4 pins for control since this is what they were designed for in the first place.