microcontrol AT89C52







AT89C52 pin diagram


AT89C52 is an 8-bit microcontroller and belongs to Atmel’s 8051 family. AT89C52 has 8KB of Flash programmable and erasable read only memory (PEROM) and 256 bytes of RAM. AT89C52 has an endurance of 1000 Write/Erase cycles which means that it can be erased and programmed to a maximum of 1000 times.


Though very slight difference between the features of AT89C51 and AT89C52, they are very similar in their pin configurations* and operations. Thedifferences between AT89C51 and AT89C52 have been tabulated below.


AT89C52 AT89C51
RAM 256 Bytes 128 Bytes
Flash 8 KB 4 KB
Number of Timers/Counters 3 (16-bit each) 2 (16-bit each)
Number of Interrupt Sources 8 6


*The pin configuration of AT89C52 is exactly similar to that of AT89C51 except that the first two pins, P1.0 and P1.1 are multiplexed to correspond to Timer2 operations as given in the following table.

Existing Alternate Function
P1.0 T2 Timer/counter 2 External Count input
P1.1 T2 EX Timer/counter 2 Trigger input


While AT89C51 has two timers (Timer0 & Timer1), AT89C52 also has Timer2. Corresponding to Timer2, there are extra SFRs (Special Function Registers) T2CON & T2MOD. Also there are registers RCAP2H & RCAP2L to configure 16 bit Capture & Auto-reload modes of Timer2.

Pin Description: 

Pin No Function Name
1 External count input to Timer/Counter 2, clock-out T2 P1.0
2 Timer/Counter 2 capture/reload trigger and direction control T2 EX P1.1
3 8 bit input/output port (P1) pins P1.2
4 P1.3
5 P1.4
6 P1.5
7 P1.6
8 P1.7
9 Reset pin; Active high Reset
10 Input (receiver) for serial communication RxD 8 bit input/output port (P3) pins P3.0
11 Output (transmitter) for serial communication TxD P3.1
12 External interrupt 1 Int0 P3.2
13 External interrupt 2 Int1 P3.3
14 Timer1 external input T0 P3.4
15 Timer2 external input T1 P3.5
16 Write to external data memory Write P3.6
17 Read from external data memory Read P3.7
18 Quartz crystal oscillator (up to 24 MHz) Crystal 2
19 Crystal 1
20 Ground (0V) Ground
21 8 bit input/output port (P2) pins/

High-order address bits when interfacing with external memory


P2.0/ A8
22 P2.1/ A9
23 P2.2/ A10
24 P2.3/ A11
25 P2.4/ A12
26 P2.5/ A13
27 P2.6/ A14
28 P2.7/ A15
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 (P0) pins 

Low-order address bits when interfacing with external memory


P0.7/ AD7
33 P0.6/ AD6
34 P0.5/ AD5
35 P0.4/ AD4
36 P0.3/ AD3
37 P0.2/ AD2
38 P0.1/ AD1
39 P0.0/ AD0
40 Supply voltage; 5V (up to 6.6V) Vcc



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