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AT89S4051  -  8-bit Microcontroller with 4K Bytes Flash  -  Atmel  -  8051

Features
• Compatible with MCS®51 Products
• 2K/4K Bytes of In-System Programmable (ISP) Flash Program Memory
– Serial Interface for Program Downloading
– Endurance: 10,000 Write/Erase Cycles
• 2.7V to 5.5V Operating Range
• Fully Static Operation: 0 Hz to 24 MHz (x1 and x2 Modes)
• Two-level Program Memory Lock
• 256 x 8-bit Internal RAM
• 15 Programmable I/O Lines
• Two 16-bit Timer/Counters
• Six Interrupt Sources
• Programmable Serial UART Channel
• Direct LED Drive Outputs
• On-chip Analog Comparator with Selectable Interrupt
• 8-bit PWM (Pulse-width Modulation)
• Low Power Idle and Power-down Modes
• Brownout Reset
• Enhanced UART Serial Port with Framing Error Detection and Automatic Address Recognition
• Internal Power-on Reset
• Interrupt Recovery from Power-down Mode
• Programmable and Fuseable x2 Clock Option
• Four-level Enhanced Interrupt Controller
• Power-off Flag
• Flexible Programming (Byte and Page Modes)
– Page Mode: 32 Bytes/Page
• User Serviceable Signature Page (32 Bytes)
 Description
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.