Special Function
Registers
The Special Function Registers (SFRs) of the AT8xC51SND2C derivatives fall into the
categories detailed in Table 31 to Table 19. The relative addresses of these SFRs are
provided together with their reset values in Table 49. In this table, the bit-addressable
registers are identified by Note 1.
Table 31. C51 Core SFRs
Mnemonic Add Name
7
6
5
4
3
2
1
0
ACC
B
E0h Accumulator
F0h B Register
PSW
SP
D0h Program Status Word
81h Stack Pointer
CY
AC
F0
RS1
RS0
OV
F1
P
DPL
DPH
82h Data Pointer Low Byte
83h Data Pointer High Byte
Table 32. System Management SFRs
Mnemonic Add Name
7
6
SMOD0
EXT16
-
5
4
3
2
GF0
XRS0
0
1
PD
0
PCON
AUXR
AUXR1
87h Power Control
SMOD1
-
M0
-
DPHDIS
-
GF1
XRS1
GF3
NV3
IDL
AO
8Eh Auxiliary Register 0
A2h Auxiliary Register 1
FBh Version Number
-
-
EXTRAM
-
ENBOOT(1)
NV5
DPS
NV0
NVERS
Note:
NV7
NV6
NV4
NV2
NV1
1. ENBOOT bit is only available in AT89C51SND2C product.
Table 33. PLL and System Clock SFRs
Mnemonic Add Name
7
-
6
-
5
-
4
-
3
2
-
1
-
0
X2
CKCON
8Fh Clock Control
E9h PLL Control
EEh PLL N Divider
EFh PLL R Divider
-
PLLRES
N3
PLLCON
PLLNDIV
PLLRDIV
R1
-
R0
N6
R8
-
-
-
PLLEN
N1
PLOCK
N0
N5
R7
N4
R6
N2
R4
R9
R5
R3
R2
Table 34. Interrupt SFRs
Mnemonic Add Name
7
6
5
4
3
2
1
0
IEN0
IEN1
IPH0
IPL0
IPH1
IPL1
A8h Interrupt Enable Control 0
EA
EAUD
EMP3
ES
ET1
EX1
ET0
EX0
B1h Interrupt Enable Control 1
-
-
-
-
-
EUSB
-
EKB
-
ESPI
EI2C
EMMC
IPHX0
IPLX0
IPHMMC
IPLMMC
B7h Interrupt Priority Control High 0
B8h Interrupt Priority Control Low 0
B3h Interrupt Priority Control High 1
B2h Interrupt Priority Control Low 1
IPHAUD
IPLAUD
IPHUSB
IPLUSB
IPHMP3
IPHS
IPLS
IPHKB
IPLKB
IPHT1
IPHX1
IPLX1
IPHSPI
IPLSPI
IPHT0
IPLT0
IPHI2C
IPLI2C
IPLMP3
IPLT1
-
-
-
-
30
AT8xC51SND2C
4341D–MP3–04/05
ATMEL [ ATMEL ]
