A Special Function Register (or Special Purpose Register, or simply Special Register) is a register within a microprocessor that controls or monitors the various functions of a microprocessor.

How many special function registers are there?

Special Function Registers (SFR's)

In 8051 micro controller there are 21 Special function registers (SFR) and this includes Register A, Register B, Processor Status Word (PSW), PCON etc etc. There are 21 unique locations for these 21 special function registers and each of these register is of 1 byte size.

Which is not a special function register?

Which of the following is not a special function register? Explanation: Accumulator is a general function register, which can be used for multiple functions. Explanation: SP is the short form of stack pointer which store address of stack top. 7.