The writemem command is a CommandPrompt command. It allows writing data to the CPU Bus.
DO NOT USE THIS COMMAND!!!
Writing the wrong data and or using the wrong address may corrupt or even damage the module. For example the Bootloader code could be damaged and the Module won't boot any more. In this case JTAG is needed to fix the problem. So if you do not exactly know, what you are doing and if you don't have a JTAG cable, do not try to use the writemem command.