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The AT89S2051/S4051 is a low-voltage, high-performance CMOS 8-bit microcontroller with 2K/4K bytes of In-System Programmable (ISP) Flash program memory.
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
AT89S2051/S4051 is a powerful microcontroller which provides a highly-flexible and
cost-effective solution to many embedded control applications. Moreover, the
AT89S2051/S4051 is designed to be function compatible with the AT89C2051/C4051
devices, respectively.
The AT89S2051/S4051 provides the following standard features: 2K/4K bytes of
Flash, 256 bytes of RAM, 15 I/O lines, two 16-bit timer/counters, a six-vector, fourlevel interrupt architecture, a full duplex enhanced serial port, a precision analog
comparator, on-chip and clock circuitry. Hardware support for PWM with 8-bit resolution and 8-bit prescaler is available by reconfiguring the two on-chip timer/counters. In
addition, the AT89S2051/S4051 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 disabling all other chip functions until the next external interrupt or
hardware reset