Features Compatible with MCS -51 Products 20K Bytes of Reprogrammable Flash Memory Endurance: 10,000 Write/Erase Cycles 4V to 5.5V Operating Range Fully Static Operation: 0 Hz to 33 MHz Three-level Program Memory Lock 256 x 8-bit Internal RAM 32 Programmable I/O Lines 8-bit Three 16-bit Timer/Counters Eight Interrupt Sources Microcontroller Programmable Serial Channel Low-power Idle and Power-down Modes with 20K Bytes Interrupt Recovery from Power-down Mode Hardware Watchdog Timer Flash Dual Data Pointer Power-off Flag Green (Pb/Halide-free) Packaging Option AT89C55WD 1. Description The AT89C55WD is a low-power, high-performance CMOS 8-bit microcontroller with 20K bytes of Flash programmable read only memory and 256 bytes of RAM. The device is manufactured using Atmels high-density nonvolatile memory technology and is compatible with the industry standard 80C51 and 80C52 instruction set and pinout. The on-chip Flash allows the program memory to be user programmed by a conventional nonvolatile memory programmer. By combining a versatile 8-bit CPU with Flash on a monolithic chip, the Atmel AT89C55WD is a powerful microcomputer which provides a highly flexible and cost effective solution to many embedded control applications. The AT89C55WD provides the following standard features: 20K bytes of Flash, 256 bytes of RAM, 32 I/O lines, three 16-bit timer/counters, a six-vector, two-level interrupt architecture, a full-duplex serial port, on-chip oscillator, and clock circuitry. In addition, the AT89C55WD is designed with static logic for operation down to zero frequency and supports two software selectable power saving modes. The Idle Mode stops the CPU while allowing the RAM, timer/counters, serial port, and interrupt system to con- tinue functioning. The Power-down Mode saves the RAM contents but freezes the oscillator, disabling all other chip functions until the next external interrupt or hardware reset. 1921DMICRO6/082. Pin Configurations 2.1 44A 44-lead TQFP P1.5 1 33 P0.4 (AD4) P1.6 2 32 P0.5 (AD5) P1.7 3 31 P0.6 (AD6) 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) 2.2 44J 44-lead PLCC P1.5 7 39 P0.4 (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) 2.3 40P6 40-lead PDIP (T2) P1.0 1 40 VCC (T2EX) P1.1 2 39 P0.0 (AD0) P1.2 3 38 P0.1 (AD1) 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) (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) GND 20 21 P2.0 (A8) 2 AT89C55WD 1921DMICRO6/08 (WR) P3.6 18 6 P1.4 (WR) P3.6 12 44 P1.4 (RD) P3.7 19 5 P1.3 (RD) P3.7 13 43 P1.3 XTAL2 20 4 P1.2 XTAL2 14 42 P1.2 XTAL1 21 3 P1.1 (T2 EX) XTAL1 15 41 P1.1 (T2 EX) 2 GND 22 P1.0 (T2) GND 16 40 P1.0 (T2) GND 17 39 NC NC 23 1 NC (A8) P2.0 18 38 VCC (A8) P2.0 24 44 VCC (A9) P2.1 19 37 P0.0 (AD0) (A9) P2.1 25 43 P0.0 (AD0) (A10) P2.2 20 36 P0.1 (AD1) (A10) P2.2 26 42 P0.1 (AD1) (A11) P2.3 21 35 P0.2 (AD2) (A11) P2.3 27 41 P0.2 (AD2) (A12) P2.4 22 34 P0.3 (AD3) (A12) P2.4 28 40 P0.3 (AD3)