According to the Blackfin Hardware Manual: "Consistent with industry-standard interfaces, multiple registers are mapped to the same address."
Specifically, looking at the defBF532.h header file, one can see that the registers are mapped in groups. One group is the UART_THR, UART_RBR and UART_DLL registers, which are all mapped to address 0xFFC00400. I can imagine that the hardware can tell if the access is to the THR or RBR register according to the operation (read or write). However, how can it distinguish between writing a character to UART_THR and setting the baud rate when writing to UART_DLL?