AT89C2051x2
Special
Function
Registers
A map of the on-chip memory area called the Special Function Register (SFR) space is shown
in the table below.
Note that not all of the addresses are occupied, and unoccupied addresses may not be imple-
mented on the chip. Read accesses to these addresses will in general return random data,
and write accesses will have an indeterminate effect.
User software should not write 1s to these unlisted locations, since they may be used in future
products to invoke new features. In that case, the reset or inactive values of the new bits will
always be 0.
Table 1. AT89C2051x2 SFR Map and Reset Values
0F8H
0FFH
0F7H
0EFH
0E7H
0DFH
0D7H
0CFH
0C7H
0BFH
0B7H
0AFH
0A7H
9FH
0F0H
0E8H
0E0H
0D8H
0D0H
0C8H
0C0H
0B8H
0B0H
0A8H
0A0H
98H
B
00000000
ACC
00000000
PSW
00000000
IP
XXX00000
P3
11111111
IE
0XX00000
SCON
SBUF
00000000
XXXXXXXX
90H
P1
97H
11111111
88H
TCON
TMOD
TL0
TL1
TH0
TH1
8FH
00000000
00000000
00000000
00000000
00000000
00000000
80H
SP
DPL
DPH
PCON
87H
00000111
00000000
00000000
0XXX0000
5
3285B–MICRO–10/03
ATMEL [ ATMEL ]
