My first question is regarding SBUF register of 8051. How come it is two registers while locations is only one i.e; 99H. we call SBUF physically two registers (write only and read only two separate distinct registers as scott mackenzie calls it in his book on 8051)? I studied the 8051 bible on hardware but the timing diagram and the circuitry shown there (Fig-13, Pg:12) was too confusing and difficult to comprehend the operation.
my next question is, where is this shift register and what has it got to how and why it shifts the bits to right. One of the books i studied online on google, mentions that shift register is external. Pardon me if i am asking very basic or easy questions but i am kinda geek in this domain and some how i havent figured out the logic behind physically two registers at same location and shift register operation and location after spending half day through different tutorials. please explain it in simple terms.