AT89C2051 pdf datasheet (8-bit

The AT89C2051 is a low-voltage, high-performance CMOS 8-bit microcomputer with
2K bytes of Flash programmable and erasable read-only memory (PEROM). The
device is manufactured using Atmel’s high-density nonvolatile memory technology
and is compatible with the industry-standard MCS-51 instruction set. By combining a
versatile 8-bit CPU with Flash on a monolithic chip, the Atmel AT89C2051 is a powerful
microcomputer which provides a highly-flexible and cost-effective solution to many
embedded control applications.
The AT89C2051 provides the following standard features: 2K bytes of Flash, 128
bytes of RAM, 15 I/O lines, two 16-bit timer/counters, a five vector two-level interrupt
architecture, a full duplex serial port, a precision analog comparator, on-chip oscillator
and clock circuitry. In addition, the AT89C2051 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 continue functioning. The power-down mode saves the
RAM contents but freezes the oscillator disabling all other chip functions until the next
hardware reset.