Russell,
I understand your code with the exception of this part:

rrc a ;get bit into carry
mov DATA,c ;out to the DATA pin
setb CLOCK
clr CLOCK ;shift it out
djnz r3,us_2

I understand that CLOCK is simply some pin on the 8051 that I set to move bits of data by triggering the A6276. But what is the DATA pin? On my prototype PCB, I have pin RXD1 from the Rigel SD51 board connected to the serial input on the A6276, but obviously I cannot shift an entire byte to a single port pin. Also, what is the purpose of the RRC command in conjunction with the carry? I understand that RRC is rotate through the carry, but why am I using it here?
I apologize for any newb questions; I bit off a bit more than I could chew with this project and am now frantically trying to make it work before it is due.

BTW: here is the link for the Allegro A6276:
http://www.allegromicro.com/sf/6276/