SFR (Special function registers) and their addresses

Registers R0-R7 are part of 128 bytes of RAM in microcontroller. Similarly registers A, B, PSW and DPTR are part of group of register known as SFR(special function registers) they have their own addresses too. They are usually accessed by their name as it is much easier. For example register A has address E0h B has F0h and so on.

See the examples.

MOV  0E0H, #55H; is same as

MOV A, #55H; which means load 55H into A

2 points need to be kept in mind.

1. First special function register have their addres between 80h to FFh. These addresses are above 80h as addresses 00h to 7Fh are addresses of RAM memory inside 8051.
2. Second, not all addresses between 80h to FFh are used by SFR. The unused location should not be used by a programmer.

Below * means bit addressable

Special function register addresses

Symbol	Name	Address
ACC*	Accumulator	0E0h
B*	Register B	0F0h
PSW*	Program Status word	0D0h
SP	Stack Pointer	81h
DPTR	Data pointer  2 bytes
DPL	Low byte	82h
DPH	High byte	83h
P0*	Port 0	80h
P1*	Port 1	90h
P2*	Port 2	0A0h
P3*	Port 3	0B0h
IP*	Interrupt priority control	0B8h
IE*	Interrupt enable control	0A8h
TMOD	Timer/counter mode control	89h
TCON	Timer/counter control	88h
T2CON	Timer/counter 2 control	0C8h
T2MOD	Timer/counter 2  mode control	0C9h
TH0	Timer/counter 0 high byte	8Ch
TL0	Timer/counter 0 low byte	8Ah
TH1	Timer/counter 1 high byte	8Dh
TL1	Timer/counter 1 low byte	8Bh
TH2	Timer/counter 2 high byte	0CDh
TL2	Timer/counter 2 low byte	0CCh
RCAP2H	T/C 2 capture register high byte	0CBh
RCAP2L	T/C 2 capture register low byte	0CAh
SCON*	Serial control	98h
SBUF	Serial data buffer	99h
PCON	Power control	87h