Summary
The internal hardware configuration of the 8051 registers and control circuits have been examined at the functional block diagram level. The 8051 may be considered to be a collection of RAM, ROM, and addressable registers that have some unique functions.
SPECIAL-FUNCTION REGISTERS
|
Register |
Bit |
Primary Function |
Bit Addressable |
|
A |
8 |
Math, data manipulation |
Y |
|
B |
8 |
Math |
Y |
|
PC |
16 |
Addressing program bytes |
N |
|
DPTR |
16 |
Addressing code and external data |
N |
|
SP |
8 |
Addressing internal RAM stack data |
N |
|
PSW |
8 |
Processor status |
Y |
|
P0-P3 |
8 |
Store I/O port data |
Y |
|
TH0/TL0 |
8/8 |
Timer/counter 0 |
N |
|
TH1/TL1 |
8/8 |
Timer/counter 1 |
N |
|
TCON |
8 |
Timer/counter control |
Y |
|
TMOD |
8 |
Timer/counter control |
N |
|
SBUF |
8 |
Serial port data |
N |
|
SCON |
8 |
Serial port control |
Y |
|
PCON |
8 |
Serial port control. user flags |
N |
|
IE |
8 |
Interrupt enable control |
Y |
|
IP |
8 |
Interrupt priority control |
Y |
|
DATA AND PROGRAM MEMORY |
||||
|
Internal |
|
Bytes |
Function |
|
|
RAM |
|
128 |
RO- R7 registers, data storage, stack |
|
|
ROM |
|
4K |
Program storage |
|
|
External |
|
Bytes |
Function |
|
|
RAM |
|
64K |
Data storage |
|
|
ROM |
|
64K |
Program storage |
|
EXTERNAL CONNECTION PINS
Function
Port pins 36 I/O, external memory, interrupts
Oscillator 2 Clock
Power 2