Special Function Registers - Jameco Atmel AT89C2051 Manual

Special Function Registers

A map of the on-chip memory area called the Special Func-
tion Register (SFR) space is shown in the table below.
Note that not all of the addresses are occupied, and unoc-
cupied addresses may not be implemented on the chip.
Read accesses to these addresses will in general return
random data, and write accesses will have an indetermi-
nate effect.
Table 1. AT89C2051 SFR Map and Reset Values
0F8H
0F0H B
00000000
0E8H
0E0H ACC
00000000
0D8H
0D0H PSW
00000000
0C8H
0C0H
0B8H IP
XXX00000
0B0H P3
11111111
0A8H IE
0XX00000
0A0H
98H SCON
00000000 XXXXXXXX
90H P1
11111111
88H TCON
00000000 00000000
80H
00000111
AT89C2051
4-18
SBUF
TMOD TL0
00000000
SP DPL
00000000
User software should not write 1s to these unlisted loca-
tions, 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.
TL1 TH0
00000000 00000000
DPH
00000000
TH1
00000000
0XXX0000
0FFH
0F7H
0EFH
0E7H
0DFH
0D7H
0CFH
0C7H
0BFH
0B7H
0AFH
0A7H
9FH
97H
8FH
PCON 87H