Features Compatible with MCS-51 Products 4K Bytes of In-System Reprogrammable Flash Memory Endurance: 1,000 Write/Erase Cycles Fully Static Operation: 0 Hz to 24 MHz Three-level Program Memory Lock 128 x 8-bit Internal RAM 32 Programmable I/O Lines Two 16-bit Timer/Counters Six Interrupt Sources Programmable Serial Channel 8-bit Low-power Idle and Power-down Modes Microcontroller Description with 4K Bytes The AT89C51 is a low-power, high-performance CMOS 8-bit microcomputer with 4K bytes of Flash programmable and erasable read only memory (PEROM). The device Flash is manufactured using Atmels high-density nonvolatile memory technology and is compatible with the industry-standard MCS-51 instruction set and pinout. The on-chip Flash allows the program memory to be reprogrammed in-system or by a conven- AT89C51 tional nonvolatile memory programmer. By combining a versatile 8-bit CPU with Flash on a monolithic chip, the Atmel AT89C51 is a powerful microcomputer which provides a highly-flexible and cost-effective solution to many embedded control applications. Not Recommended PDIP Pin Configurations for New Designs. P1.0 1 40 VCC P1.1 2 39 P0.0 (AD0) P1.2 3 38 P0.1 (AD1) Use AT89S51. P1.3 4 37 P0.2 (AD2) P1.4 5 36 P0.3 (AD3) P1.5 6 35 P0.4 (AD4) P1.6 7 34 P0.5 (AD5) P1.7 8 33 P0.6 (AD6) RST 9 32 P0.7 (AD7) PQFP/TQFP (RXD) P3.0 10 31 EA/VPP (TXD) P3.1 11 30 ALE/PROG (INT0) P3.2 12 29 PSEN (INT1) P3.3 13 28 P2.7 (A15) (T0) P3.4 14 27 P2.6 (A14) (T1) P3.5 15 26 P2.5 (A13) (WR) P3.6 16 25 P2.4 (A12) (RD) P3.7 17 24 P2.3 (A11) XTAL2 18 23 P2.2 (A10) XTAL1 19 22 P2.1 (A9) P1.5 1 33 PO.4 (AD4) GND 20 21 P2.0 (A8) P1.6 2 32 P0.5 (AD5) P1.7 3 31 P0.6 (AD6) PLCC RST 4 30 P0.7 (AD7) (RXD) P3.0 5 29 EA/VPP NC 6 28 NC (TXD) P3.1 7 27 ALE/PROG (INT0) P3.2 8 26 PSEN (INT1) P3.3 9 25 P2.7 (A15) (T0) P3.4 10 24 P2.6 (A14) (T1) P3.5 11 23 P2.5 (A13) P1.5 7 39 PO.4 (AD4) P1.6 8 38 P0.5 (AD5) P1.7 9 37 P0.6 (AD6) RST 10 36 P0.7 (AD7) (RXD) P3.0 11 35 EA/VPP NC 12 34 NC (TXD) P3.1 13 33 ALE/PROG (INT0) P3.2 14 32 PSEN (INT1) P3.3 15 31 P2.7 (A15) (T0) P3.4 16 30 P2.6 (A14) (T1) P3.5 17 29 P2.5 (A13) Rev. 0265G02/00 1 (WR)P3.6 12 44 P1.4 (RD) P3.7 13 43 P1.3 XTAL2 14 42 P1.2 XTAL1 15 41 P1.1 (T2 EX) GND 16 40 P1.0 (T2) GND 17 39 NC (A8) P2.0 18 38 VCC (A9) P2.1 19 37 P0.0 (AD0) (A10) P2.2 20 36 P0.1 (AD1) (A11) P2.3 21 35 P0.2 (AD2) (A12) P2.4 22 34 P0.3 (AD3) (WR)P3.6 18 6 P1.4 (RD) P3.7 19 5 P1.3 XTAL2 20 4 P1.2 XTAL1 21 3 P1.1 GND 22 2 P1.0 NC 23 1 NC (A8) P2.0 24 44 VCC (A9) P2.1 25 43 P0.0 (AD0) (A10) P2.2 26 42 P0.1 (AD1) (A11) P2.3 27 41 P0.2 (AD2) (A12) P2.4 28 40 P0.3 (AD3)Block Diagram P0.0 - P0.7 P2.0 - P2.7 V CC PORT 0 DRIVERS PORT 2 DRIVERS GND RAM ADDR. PORT 0 PORT 2 RAM FLASH REGISTER LATCH LATCH PROGRAM STACK B ACC ADDRESS POINTER REGISTER REGISTER BUFFER TMP1 TMP2 PC INCREMENTER ALU INTERRUPT, SERIAL PORT, AND TIMER BLOCKS PROGRAM COUNTER PSW PSEN TIMING ALE/PROG INSTRUCTION AND DPTR REGISTER EA / V CONTROL PP RST PORT 1 PORT 3 LATCH LATCH OSC PORT 1 DRIVERS PORT 3 DRIVERS P1.0 - P1.7 P3.0 - P3.7 2 AT89C51