VxWorks A detailed explanation of the startup process (Part I)

VxWorks has three images:

VxWorks image has three types of files

1. Loadable Images: Downloaded to ram by Boot-rom via the network port or serial port
2. rom-based Images (compressed/uncompressed): The image is burned directly into the ROM, executed when the image is copied into RAM.
3. The instruction portion of the Rom-resident images:image resides in ROM execution. Only part of the data segment is copied into RAM.

Note that the three images mentioned here are images that include the real operating system VxWorks, the latter two of which can be started and executed directly. But the first one doesn't, it has to be done with an image called Boot image (which can be generated in the Build->build boot ROM in tornado), that is, using the boot The image is then booted up and then downloaded from the network port or serial port to really include the VxWorks loadable Image, then the ability to execute.

This means that the boot image is used in conjunction with loadable image.

Now it looks like you have four image files in common. Let's take a look at their composition:

1. Boot Image: Includes a program called Bootstrap programs + a ROM BOOT program.
2. Loadable Images: An image consisting of an operating system VxWorks and an application.
3. rom-based Images (compression/No compression): includes a program called Bootstrap programs + Loadable Images (i.e. an image with operating system VxWorks and application composition)
4. Rom-resident Images: Ibid.

By the above we can see. Rom-based images,rom-resident Images. Boot Image

All three images include a program called Bootstrap programs, which has a startup function. The ability to copy code snippets and data segments from ROM to ram; Let's look at the boot process for three vxworks:

• Boot Image + Loadable Images:

We said that the loadable images was loaded on boot image. First, the program in boot image bootstrap programs to load the boot program into Ram_high_adrs in RAM . Then control is given to the boot program. The boot program is responsible for a series of simple hardware initialization (network port, serial port, etc.), starting to download loadable Images (including the application's VxWorks operating system) to Ram_low_adrs, and then control to the VxWorks operating system to start running.

The following figure one is a simple flowchart, and the latter is a more specific flowchart.

Figure A

Figure II (1)

Figure II (2)

• rom-based Images (compression/No compression):

Such an image can be started directly because it includes the bootstrap programs program itself. So there is no need to boot programme in such an image, first bootstrap programs boot, the VxWorks in the image is loaded into the memory Ram_low_adrs and start execution. Figure three is a schematic diagram, figure IV is a more detailed flowchart.

Might

Figure Four

• Rom-resident Images:

The loading of such images and the previous one are basically the same kind. Just load only part of data section and BSS only.

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VxWorks A detailed explanation of the startup process (Part I)