Stack Pointer

• Stack pointer is a 8 bit register with address 81H.
• It pointes the address of current stack memory location.
• While pushing data into stack memory stack pointer is incremented by 1.
• If data is retrieved from stack memory stack pointer is decremented by 1.
•  Designer can stack pointer register from first memory location of stack memory by inserting address of first location of stack memory.

 

MOV SP, # 5FH

• In 8051 stack memory is of 32 byte with starting address of 5FH and ending address of 7FH.

 

Register B:

• This is 8 bit register.
• Used with accumulator in the process of multiplication and division.
• In case of multiplication 8 bit output is stored in accumulator while upper 8 bits are stored in register.
• In division result is stored accumulator while remainder is stored in register B.