AT89C4051
6. Special Function Registers
A map of the on-chip memory area called the Special Function Register (SFR) space is shown in
the
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 6-1.
0F8H
0F0H
0E8H
0E0H
0D8H
0D0H
0C8H
PSW
00000000
ACC
00000000
B
00000000
AT89C4051 SFR Map and Reset Values
0FFH
0F7H
0EFH
0E7H
0DFH
0D7H
0CFH
0C7H
0C0H
0B8H
0B0H
0A8H
0A0H
SCON
00000000
P1
11111111
TCON
00000000
TMOD
00000000
SP
00000111
TL0
00000000
DPL
00000000
TL1
00000000
DPH
00000000
TH0
00000000
TH1
00000000
PCON
0XXX0000
SBUF
XXXXXXXX
IP
XXX00000
P3
11111111
IE
0XX00000
0BFH
0B7H
0AFH
0A7H
9FH
97H
8FH
87H
98H
90H
88H
80H
5
1001F–MICRO–6/08
ATMEL [ ATMEL CORPORATION ]
