Rainbow Electronics AT89C4051 - Manual (Page 5)

5
AT89C4051
1001D–06/01
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
implemented on the chip. Read accesses to these addresses will in general return ran-
dom 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. AT89C4051 SFR Map and Reset Values
0F8H 0FFH
0F0H B
00000000
0F7H
0E8H 0EFH
0E0H ACC
00000000
0E7H
0D8H 0DFH
0D0H PSW
00000000
0D7H
0C8H 0CFH
0C0H 0C7H
0B8H IP
XXX00000
0BFH
0B0H P3
11111111
0B7H
0A8H IE
0XX00000
0AFH
0A0H 0A7H
98H SCON
00000000
SBUF
XXXXXXXX
9FH
90H P1
11111111
97H
88H TCON
00000000
TMOD
00000000
TL0
00000000
TL1
00000000
TH0
00000000
TH1
00000000
8FH
80H SP
00000111
DPL
00000000
DPH
00000000
PCON
0XXX0000
87H