TS-Bootrom

This section describes what code is executed when a system is powered on or reset using our TS-BOOTROM. The sequence is:

• CPU BootROM
• TS-BOOTROM
• Linux kernel
• linuxrc (initrd)
• Debian init
• Embedded application

The Debian init step may be excluded on systems that do not require Debian.

This board does not support U-Boot, RedBoot, or other standard bootloaders. The TS-BOOTROM is optimized for speed. This makes our systems ideal for applications that need to start immediately upon power-up. The TS-BOOTROM performs basic register initializations and RAM initialization, and then it selects a boot media based on jumper settings. If the media indicated by the jumper is clearly not bootable, the bootrom may fall back and boot from the other device.

Once the boot media is chosen, the TS-BOOTROM passes control to the 446 bytes of code found in the MBR. This code scans the partition table for partitions with an ID of 0xDA. The first partition found with this magic ID is loaded into RAM and treated as a kernel binary. If a second partition with this id is found, it is loaded into RAM and treated as an initial ramdisk. When this is done, execution jumps into the kernel.

For the small minority of systems that have a need to perform other behavior at boot time instead of executing a Linux kernel, developers will need to fully understand the functionality of the TS-BOOTROM. Second stage bootloaders, custom microcontroller-style binaries, or other operating systems can be loaded by TS-BOOTROM as long as they have an execution entry point in the same place as the Linux kernel would have on the particular System-on-Module in question. Contact embeddedTS if you need to execute a binary besides Linux.