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Maxim > Design Support > Technical Documents > Application Notes > Microcontrollers > APP 3262
Keywords: in-system programming, software upgrade, field upgrade, bootloader, bootstrap loader, 8051,
microcontroller
APPLICATION NOTE 3262
In-System Programming with 8051-Based
Microcontrollers
By: Kevin Self
Aug 10, 2004
Abstract: In-system programming is a valuable feature that allows system firmware to be upgraded
without disassembling the embedded system to physically replace memory. Most Maxim 8051-based
microcontrollers can be reprogrammed from a PC or laptop via an inexpensive RS-232 serial interface
and a few logic gates. When launched, the in-system programming feature autobauds to the detected
baud rate and begins execution of a command-driven, ROM-based bootstrap loader. The free, PC-
based Microcontroller Tool Kit programming utility is available from Maxim.
Embedded designs with in-system programmability allow generic products to be software-customized
right before shipment. The feature also reduces life cycle cost by permitting existing applications to be
upgraded without disassembling the application. Secure microcontrollers such as the DS5002FP and
DS5250 can use this feature to load the customer's proprietary software into the application where it will
be automatically encrypted and protected against unauthorized access.
Introduction
Many members of the Maxim 8051-based microcontroller family support in-system programming via a
commonly available RS-232 serial interface. In-system programming means that the program and/or
data memory can be modified without disassembling the embedded system to physically replace
memory. With an emphasis on ease-of-use and versatility, this feature adds a number of very valuable
features in any embedded design:
Allows hardware to be assembled and stocked at the factory and software-customized right before
shipment,
Eliminates high cost of disassembling units in field when software updates are required,
Allows for software upgrades in physically inaccessible locations,
Accesses dedicated configuration and status registers, and
Enables the loading of software into secure microcontrollers with memory encryption.
Devices with this feature include:
Secure Microcontroller Modules: DS2250, DS2250T, DS2251T, DS2252T, DS5000,
DS5000T
Secure Microprocessors: DS5000FP, DS5001FP, DS5002FP, DS5002FPM
High-Speed Secure Microprocessor: DS5250
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