IC80C51 Datasheet, PDF (8/44 Pages) Integrated Circuit Solution Inc – CMOS SINGLE CHIP 8-BIT MICROCONTROLLER

IC80C51
IC80C31
SPECIAL FUNCTION REGISTERS
The Special Function Registers (SFR's) are located in
upper 128 Bytes direct addressing area. The SFR Memory
Map in Figure 6 shows that.
Not all of the addresses are occupied. Unoccupied
addresses are not implemented on the chip. Read accesses
to these addresses in general return random data, and
write accesses have no effect.
User software should not write 1s to these unimplemented
locations, since they may be used in future microcontrollers
to invoke new features. In that case, the reset or inactive
values of the new bits will always be 0, and their active
values will be 1.
The functions of the SFRs are outlined in the following
sections, and detailed in Table 2.
Accumulator (ACC)
ACC is the Accumulator register. The mnemonics for
Accumulator-specific instructions, however, refer to the
Accumulator simply as A.
B Register (B)
The B register is used during multiply and divide operations.
For other instructions it can be treated as another scratch
pad register.
Program Status Word (PSW). The PSW register contains
program status information.
Upper
128
Not Available
in
IC80C51/31
80H
7FH
Lower
128
Accessible
by Direct
and Indirect
Addressing
0
FFH
F8
F0
B
E8
Accessible
by Direct
Addressing
E0 ACC
D8
D0 PSW
C8
C0
B8
IP
B0 P3
80H
A8
IE
A0 P2
98 SCON SBUF
90 P1
Ports,
88 TCON TMOD
TL0
TL1
TH0
TH1
Status and
80 P0
SP
DPL
DPH
Special
Function
Registers
Control Bits,
Timer,
Registers,
Stack Pointer,
Bit
Addressable
Accumulator
(Etc.)
Figure 6. Internal Data Memory and SFR Memory Map
FF
F7
EF
E7
DF
D7
CF
C7
BF
B7
AF
A7
9F
97
8F
PCON 87
S3-8
78
70
68
60
58
50
48
40
38
30
28
20 ^{0 ...}
18
10
08
00
8 BYTES
BANK3
BANK2
BANK 1
BANK 0
7F
77
6F
67
5F
SCRATCH
57
PAD
4F
AREA
47
3F
37
...7F
2F
BIT
ADDRESSABLE
27
SEGMENT
1F
17
REGISTER
0F
BANKS
07
Figure 7. Lower 128 Bytes of Internal RAM
Integrated Circuit Solution Inc.
MC001-0B