8051 Microcontrollers

Proven, capable, royalty-free 8/16-bit MCUs

8051-compatible microcontroller cores continue to be smart choices for simple applications or to offload a main processor in larger SoCs. 

These reusable soft 8051 cores are among the most feature-rich and customer-proven available anywhere. 

They offer configurable CPUs and bundled peripherals, 8-bit area and power savings, easy development and test, proven reliability, and royalty-free value. 

Explore our 8051 family here, then give us a call or email to discuss your needs and arrange an evaluation.

Your Best Source of 8051 Cores

Since 1998 and over four generations of improving code, more than two hundred CAST customers have gotten a competitive edge with these ASIC and FPGA cores for the MCS®51 instruction set.

Our 8051s give you: 

  • Configurability from very fast to very small, with the peripherals of your choice, 
  • Seamless integration with IAR Systems and Keil tools for easier software development
  • Libraries, an instruction set simulator, and reference design boars for easy eval and quick development, 
  • Four-wire JTAG or Single-Wire on-chip debug for when every pin matters, and 
  • Cost-effective pricing with project-based licensing (no royalties).

Whether you need a basic embedded controller or want to handle housekeeping functions for a main SoC processor, consider the benefits of these proven microcontrollers.

Key Stats

Up to
69.7x DMIPS/MHz
of original 80c51 (26.9x for 8-bit)

Up to
500 MHz

Power usage from
0.021 mW/MHz

Area from
6k gates

Figures are for TSMC 90nm.
See individual core pages for more sample implementation results.


Super-Fast S8051XC3 MCU Core 

• 26.85x faster than original, very configurable

Tiny T8051XC3

• 3.3K gates (CPU), 7.94x faster

Mature R8051XC2 MCU Core

• 12.1x, 3rd-gen code, inexpensive

Legacy L8051XC1 MCU Core 

• Timing-configurable for ideal replacement

CAST 8051 customers have shipped billions of units. You can too.

SDIC Uses CAST 8051 IP Cores

SDIC Licenses 8051 Microcontroller IP Cores from CAST

“We excel at developing innovative yet cost-competitive ICs to drive a variety of consumer and medical devices,” said Li Jian, general manager of the SDIC Shanghai Branch. “The mature, flexible 8051 IPs from CAST with their unique one-wire debugging feature allow us to add features and capabilities while reducing costs, plus CAST’s quick and effective technical support helps keep our projects on schedule despite demanding client delivery deadlines.”

CAST 8051 IP Subsystem for CAN FD Transceiver Development Utilized by ON Semiconductor

“Not only did CAST have the CAN FD controller and working subsystem board before anyone else, their long experience with CAN IP and reputation for great support and service made our decision easy, really jumpstarting our early transceiver development project,” said Roman Buzas, application manager for IVN products at ON Semiconductor.

GIT Japan Uses CAST 8051 in AIST’s MEMS-EFS Electrostatic Sensor

“CAST’s efficient, easy-to-use 8051 core was an excellent solution for our challenge of building AIST’s innovative electrostatic field sensor system,” said Yoshinori Nakagawa, design engineer for GIT Japan.

CAST‘s 200th 8051 IP Core License Goes to Ensphere Solutions

“CAST’s 8051 controller offered the best combination of features, performance, and terms that we could find,” said Emad Afifi, vice president of engineering for Ensphere Solutions. “The proven track record of both the 8051 core and the support team at CAST give us great confidence as we pursue this next great engineering challenge.”

Kawasaki Microelectronics Licenses CAST 8051 IP Core for New Design Platform

"This 8051 IP combines high performance and ease of use to provide customers a quick and effective solution at an affordable price. We expect this valuable IP will contribute to increase our presence in the current tough market, especially in Asia," said Yusuke Yamamoto, K-micro senior manager, Marketing & Strategic Planning Department.

Try Our 8051s for Yourself

Cycle-accurate software simulators and Talos Series Evaluation Kits with the core running on an FPGA board make it easy to test our 8051s in your own environment.

Native On-Chip Debug Package

Use leading IDEs with an optional, native on-chip debug block and inexpensive external adapter(pod) with a JTAG four-wire or SWAT Single-Wire PC interface.

Enjoy Rapid Development with Your Choice of Leading IDEs 

“The simplicity and long history of 8051 coding coupled with these great IDEs mean designers can now deliver effective 8051-based subsystems quicker—and cheaper—than possible for perhaps any other microcontroller.” Maciej Pyka, president of Silesia Devices

IAR Systems® Embedded Workbench® for 8051

A complete, modern integrated design environment for 8051 programming.


ARM® Keil™ µVision4 IDE for 8051

A long-running, proven IDE for effective 8051 programming.

Products in Family

Super-Fast 8051 Microcontroller with Configurable Features & Peripherals

High-Performance, Configurable, 8-bit Microcontroller

Ultra-Small 8051-Compatible Microcontroller

Legacy-Configurable 8051-Compatible Microcontroller IP

Let's talk about your project and our IP solutions

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