I am not entire sure but based on my knowledge, i think the Interactive C has hidden the machine code from u. That means when u download a program to the board, the Interactive C actually converts your C code into machine code, send the code through the serial port to the 6811. The 6811 then will do the required operations, for instance, write to memory, based on the machine code.
Of course, data can also be written to the SRAM by not only the 6811 but also other devices. However, i think at the end, the Interactive C will still have to tell the 6811 where to read the data.
Someone please correct me if I am wrong. Thanks.