I'm afraid the two I can think of have non-publicly available data sheets: one is a cablecrypto device, the other a SLIC. The SLIC is the one with the daisy chain - they want to be able to build phone systems with a SLIC for every slot in a T1 frame - so 24 SLICs - they're trying to avoid 24 CS pins and 24 interrupts on the attached signalling CPU