ROM Patching Circuit

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ROM Patching Circuit

Embedded microcontrollers normally use on-chip embedded flash memory to save system and user application code. However, if the microcontroller task is pretty much determined, the firmware code is also known at SOC design phase and no need to reload and burn the whole firmware in field. In this case, ROM can be a good alternative to on-chip flash memory due to high storage density, low power, and high access speed.


However, ROM does necessitate the programming of perfect and complete code and data when the chip is created. By the nature of the ROM structure, it is impossible to reprogram or rewrite ROM. In reality, there are several reasons for wanting to be able to make changes to ROM code after chip is manufactured. In some cases, electronic products are often developed in short time frames and released without exhaustive testing, therefore ‘bugs’ or defects in the ROM code may be discovered after products have been released on the market. Other circumstances such as a change in operating parameters or conflicting hardware or software may necessitate later alteration of the operating code residing in the ROM.

Therefore how to alter or patch ROM code is normally a must have for ROM based microcontroller chips. This article discusses the normal way how to achieve it.


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Highlights: 696 words, 3 images
ASIC engineer
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1 Comment
  1. cLeary 2 years ago

    Most MCUs use flash memory. ROM patching is rarely seen. But good reading.


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