8-BIT Microcontroller

Features· Compatible with MCS-51 Products · 4 Kbytes of In-System Reprogrammable Flash MemoryEndurance: 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 · Low Power Idle and Power Down Modes

Pin Configurations PDIP/CerdipDescriptionThe AT89C51 is a low-power, high-performance CMOS 8-bit microcomputer with 4Kbytes of Flash Programmable and Erasable Read Only Memory (PEROM). Thedevice is manufactured using Atmel’s high density nonvolatile memory technologyand is compatible with the industry standard MCS-51Ô instruction set and pinout.The on-chip Flash allows the program memory to be reprogrammed in-system or bya conventional nonvolatile memory programmer. By combining a versatile 8-bit CPUwith Flash on a monolithic chip, the Atmel AT89C51 is a powerful microcomputerwhich provides a highly flexible and cost effective solution to many embedded controlapplications.

The AT89C51 provides the following standard features: 4Kbytes of Flash, 128 bytes of RAM, 32 I/O lines, two 16-bittimer/counters, a five vector two-level interrupt architecture,a full duplex serial port, on-chip oscillator and clockcircuitry. In addition, the AT89C51 is designed with staticlogic for operation down to zero frequency and supportstwo software selectable power saving modes. The IdleMode stops the CPU while allowing the RAM, timer/counters,serial port and interrupt system to continue functioning.The Power Down Mode saves the RAM contents butfreezes the oscillator disabling all other chip functions untilthe next hardware reset.

When the AT89C51 is executing code from external programmemory, PSEN is activated twice each machine cycle,except that two PSEN activations are skipped duringeach access to external data memory.EA/VPPExternal Access Enable. EA must be strapped to GND inorder to enable the device to fetch code from external programmemory locations starting at 0000H up to FFFFH.Note, however, that if lock bit 1 is programmed, EA will beinternally latched on reset.EA should be strapped to VCC for internal program executions.This pin also receives the 12-volt programming enablevoltage (VPP) during Flash programming, for parts that require12-volt VPP.XTAL1Input to the inverting oscillator amplifier and input to theinternal clock operating circuit.XTAL2Output from the inverting oscillator amplifier.