How does MBR know of the Bootloader's start address when SD is absent?

Question

I am planning to use Open bootloader example as my starting point for adding a bootloader to an application. I donot want Softdevice. Initially I am going to check the dfu functionality once I get this right. Below are the steps I am planning to follow. Please let me know if anything is wrong 1. Cut the MBR out of Softdevice S140 hex (First 4k bytes) Ref: devzone.nordicsemi.com/.../126351 2. Flash the MBR using nrf_go studio 3. Build and flash the bootloader using nrf_go studio 4. Build and flash any application, say blinky using nrf_go studio 
 Queries: 1. How does MBR know of the Bootloader's start address? Is this relevant - https://devzone.nordicsemi.com/f/nordic-q-a/26300/how-to-use-nrfjprog-to-write-uicr-bootloaderaddr 2. Is the transfer of IRQ table from Bootloader to App taken care of by Open Bootloader example? 
 Caveat: My device lost the JLink bin used for JLink debugger when I earlier used the nrf_go studio. Still clueless why this happened and how this can be avoided - https://devzone.nordicsemi.com/f/nordic-q-a/46273/nrf-board-not-getting-detected

Vidar Berg · Accepted Answer

Hi, 
 I would recommend using the standalone version of the MBR is included in the SDK 15.3.0: 
RF5_SDK_15.3.0_59ac345\components\softdevice\mbr
rf52840\hex 
 1. Yes, the bootloader address is either stored in the UICR (@0x10001014) or in the MBR at MBR_BOOTLOADER_ADDR if you use the bootloader from SDK 15.3.0 
 2. Yes, the open bootloader changes the interrupt forwarding before booting the app. 
 Caveat: My device lost the JLink bin used for JLink debugger when I earlier used the nrf_go studio. 
 This can happen if you press the reset button while power-cycling the board. It only affects the interface MCU(jlink lite), not the nRF chip.

How does MBR know of the Bootloader's start address when SD is absent?

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