After the modules come off the assembly line at the factory, they are equipped with a basic software, the so called Boot Loader. This is kind of a “Mini-OS”, supplying the module with some basic functions. The Boot Loader is stored in the “Monitor” segment of the flash memory.
The Boot Loader contains the following functions:
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Immediatley after switching on, the microcontroller identifies itself and the module it is mounted in respectively.
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By use of the BooT Loader, the microcontroller can communicate via the serial port.
If there is no firmware in the memory of the module yet, the Boot Loader allows the firmware data to be copied via the serial port to the adjacent memory block.
If there is already a firmware in the memory of the microcontroller, it is started by the Boot Loader. After that, the firmware code is executed; the Boot Loader has done its job.
For security reasons, the memory of the Boot Loader can not be accessed by users. After production, the Boot Loader Code is once copied to the memory and kept there forever. This way, it is always possible to communicate with a microcontroller via a serial connection. This connection can also be always used to install or update the firmware; even if the data in the memory is faulty or incomplete.
If no valid firmware is available in the next memory block, the startup call for the firmware has failed or booting has been stopped for security reasons, the module remains in the so called Monitor condition.
![[Important]](../pics/important.gif)
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Important |
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Do not to mix up the terms Monitor with the monitoring of audio signals using a Monitor bus. This term comes from the history of computer development and describes the very first, most basic piece of software in a computer system. |
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You can recognize a module in monitor condition: in the Maintenance Window of the Toolbox4 sofware, ist ID is replaced by the termMONITOR in the tree view. The following figure shows an example for this:
The highlights in the figure show how the condition of a module can be recognized. If only the Boot Loader was loaded, an unknown module is shown in the Device view module tree of the Maintenance Window.
According to the type of connection between PC and DSP frame, the display differs:
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Ethernet: unknown module
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Serial: Monitor + Prozessor-Seriennummer (PN)
Also, you can have the detailed information of the unknown module displayed. You recognize a module with Boot Loader but without firmware by the firmware version 05.00.06.146.
To have the detailed information displayed, highlight the desired module and then press the F11 key. Alternatively, you can also use the command from the menu or contextual menu.