Microcontrollers
581
P0.0-P0.7
Port 0
Drivers
P2.0-P2.7
Port 2
Drivers
P1.0-P1.7
Port 1
Drivers
P3.0-P3.7
Port 3
Drivers
RAM ADDR
Register
RAM
Port 0
Latch
Port 2
Latch
RAM/EPROM
B
Register
TMP2
TMP1
Stack
Pointer
ALU
PSW
SFRs
Timers
Port 1
Latch
Port 3
Latch
Program
address
register
Buffer
PC incrementer
Program
counter
DPTR's
Multiple
ACC
Timing
and
Control
n
o
i
t
c
u
r
t
s
n
I r
e
t
s
i
g
e
R
PD
Oscillator
PSEN
ALE/PROG
EAV PP
RST
XTAL 1
XTAL 2
VCC
VSS
8
8
16
Figure 14.16 Architecture of the 80C51 microcontroller family.
an eight-bit wide stack pointer and a 16-bit wide program counter. Special-function registers include
program status word (PSW), data pointer (DPTR), timer registers, control registers and capture registers.
Addressing Modes
The 80C51 family of microcontrollers supports five addressing modes including register addressing,
direct addressing, register indirect addressing, immediate addressing and base register plus index
register addressing.