USED Atmel At89c52 Microcontroller

Pin No

Function

Name

1

External count input to Timer/Counter 2, clock-out

T

P.0

2

Timer/Counter 2 capture/reload trigger and direction control

T EX

P.1

3

8 bit input/output port (P) pins

P.2

4

P.3

5

P.4

6

P.5

7

P.6

8

P.7

9

Reset pin; Active high

Reset

10

Input (receiver) for serial communication

RxD

8 bit input/output port (P) pins

P.0

11

Output (transmitter) for serial communication

TxD

P.1

12

External interrupt 1

Int0

P.2

13

External interrupt 2

Int1

P.3

14

Timer1 external input

T

P.4

15

Timer2 external input

T

P.5

16

Write to external data memory

Write

P.6

17

Read from external data memory

Read

P.7

18

Quartz crystal oscillator (up to 24 MHz)

Crystal 2

19

Crystal 1

20

Ground (0V)

Ground

21

8 bit input/output port (P) pins

/

High-order address bits when interfacing with external memory

P.0/ A

22

P.1/ A

23

P.2/ A

24

P.3/ A

25

P.4/ A

26

P.5/ A

27

P.6/ A

28

P.7/ A

29

Program store enable; Read from external program memory

PSEN

30

Address Latch Enable

ALE

Program pulse input during Flash programming

Prog

31

External Access Enable; Vcc for internal program executions

EA

Programming enable voltage; 12V (during Flash programming)

Vpp

32

8 bit input/output port (P) pins

Low-order address bits when interfacing with external memory

P.7/ AD

33

P.6/ AD

34

P.5/ AD

35

P.4/ AD

36

P.3/ AD

37

P.2/ AD

38

P.1/ AD

39

P.0/ AD

40

Supply voltage; 5V (up to 6.6V)

Vcc