Read-Modify-Write Flash

This article describes how to use the Read-Modify-Write(RMW) function of J-Link. This article assumes that there is already a basic knowledge about flash programming in general. The following example project will be shown for a Infineon XMC4500 MCU but can be applied to any other MCU which gives the option to split up physical memory sectors into smaller logical ones.

By default the Read-Modify-Write threshold is set to 1 kB.

To increase the threshold J-Link offers the following command string: SetFlashDLNoRMWThreshold = <value>

A more detailed description is available in the J-Link users manual(UM8001).

Minimum requirements

In order to use the example project the following minimum requirements have to be met:

• J-Link software version V6.14a or later
• J-Link Plus HW version V10.1 or later
• Windows PC to execute the .bat file in the example project

Sample project

The sample project is designed to be used with J-Link Plus and a Infineon XMC4500 MCU. It will we automatically executed when starting the .bat file.

The .bat and .jlink file can be used as a reference for your own RMW flash projects.

How to

For the example project the SetFlashDLNoRMWThreshold value was set to 0xC00FFFF(device specific). Make sure you adjust this value depending on the device and sector you are trying to modify.

To use the example project follow these steps:

• Unzip the contents of the Wiki_RMW.zip to a example folder
• execute StartTest.bat
• The J-Link commander will open and you should see the following output

• If your output matches the screenshot, the RMW was successful(this applies only to the example project, the output on your own project might vary)