[Elecraft] KAT500 Band Data Input Question

[Randy Farmer]

I have a brand new KAT500 coming, to be delivered tomorrow. I'm now 
trying to figure how to integrate it into my SO2R contest station. I've 
looked at the manual and done research in the reflector archives, but 
I'm still unsure what it takes to make the tuner change bands. I have a 
simple question:

Will the KAT500 respond to BCD band data alone at its control input or 
is it also necessary for it to be connected to the Aux Bus (like the 
KPA500) for it to change bands under positive hardware control?

I need to rig a way to share the tuner control between two dissimilar 
radios. The primary radio is a K3, so there's no problem there. The 
secondary radio is an old Yaesu FT-1000D, which obviously can't 
communicate on the Aux Bus. My station setup will allow me to create and 
select TTL band data for the appropriate radio, but it's not clear to me 
that this is enough to control the tuner. I was quite surprised to find 
out that the KPA500 wouldn't support control using band data commands 
alone, and I'm afraid the KAT500 may share the same "feature". This 
limitation really impedes the amp's usability in an automated station 
using other than Elecraft radios, probably for sound technical reasons 
that I don't quite understand. Can anyone tell me for sure how the 
KAT500 is controlled?

73...
Randy, W8FN