& symbol in PRU

Why is there an ampersand in front of the register of the first argument of commands like SBBO and LBBO?
old format, from PASM: LBBO r10, r20, 0, 4
new format compiled with clpru: LBBO &r0, r0, 16, 4
If I remove the ampersand, I get invalid instruction. This says to me that it is providing the address of the register, rather than the content. Is there a case when you would want to provide a different address than any of the registers, and you can load into that?