Special Function
Registers
A map of the on-chip memory area called the Special Function Register (SFR) space is
shown in Table 1.
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.
Timer 2 Registers Control and status bits are contained in registers T2CON (shown in
Table 2) and T2MOD (shown in Table 9) for Timer 2. The register pair (RCAP2H,
RCAP2L) are the Capture/Reload registers for Timer 2 in 16-bit capture mode or 16-bit
auto-reload mode.
Table 1. AT89S8252 SFR Map and Reset Values
0F8H
0FFH
0F7H
0EFH
0E7H
B
0F0H
00000000
0E8H
ACC
0E0H
00000000
0DF
H
0D8H
PSW
0D0H
SPCR
000001XX
0D7H
00000000
T2CON
00000000
T2MOD
XXXXXX00
RCAP2L
00000000
RCAP2H
00000000
TL2
00000000
TH2
00000000
0CF
H
0C8H
0C0H
0B8H
0B0H
0A8H
0A0H
98H
0C7H
0BFH
0B7H
0AFH
0A7H
9FH
IP
XX000000
P3
11111111
IE
SPSR
00XXXXXX
0X000000
P2
11111111
SCON
00000000
SBUF
XXXXXXXX
P1
11111111
WMCON
00000010
90H
97H
TCON
00000000
TMOD
00000000
TL0
00000000
TL1
00000000
TH0
00000000
TH1
00000000
88H
8FH
P0
11111111
SP
00000111
DP0L
00000000
DP0H
00000000
DP1L
00000000
DP1H
00000000
SPDR
XXXXXXXX
PCON
0XXX0000
80H
87H
6
AT89S8252
0401G–MICRO–3/06
ATMEL [ ATMEL ]
