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8051 Device Support

The 8051 Family is one of the fastest growing Microcontroller Architectures. More than 500 device variants from various silicon vendors are available today. New extended 8051 devices, like the Philips 80C51MX architecture, are dedicated for large applications with several megabytes of code and data space.

For optimum support of these different 8051 variants, Keil provides several development tools that are listed in the table below. A new output file format (OMF2) allows direct support of up to 16MB code and data space. The CX51 Compiler is a variant of the C51 compiler that is designed for the new Philips 80C51MX architecture.

Development Tools Supported Microcontrollers Description
C51 Compiler,
A51 Macro Assembler,
BL51 Linker/Locater
Classic 8051 Devices. Supports standard 8051 devices and includes support for 32 x 64K code banks.
C51 Compiler
(with OMF2 Output),
AX51 Macro Assembler,
LX51 Linker/Locater
Classic 8051 Devices,
Extended 8051 Variants,
Dallas 390/52xx/400/41x.
Supports standard and extended 8051 devices. Includes support for code banking and up to 16MB code and xdata memory.
CX51 Compiler,
AX51 Macro Assembler,
LX51 Extended
Philips 80C51MX Devices. Supports Philips 80C51MX devices that provide a linear 16MB address space.

The Cx51 Compiler is available in different packages. The table above refers to the entire line of the 8051 development tools.


  • The term Cx51 refers to both the C51 Compiler and the CX51 Compiler.
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