Hardware reference guide

Chapter 3: The Software
Boot Types
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7535 Hardware Reference Guide
• the first time the terminal is turned on at the factory (‘initial software load’)
• the terminal is turned on after it is powered down (‘cold boot’)
• the terminal is turned on after it was suspended (‘resume from suspend’).
The most common type of boot is the resume from suspend. When the 7535 is
turned off, it enters a ‘suspended’ state, where its main processor is stopped, but
retains the contents of its RAM.
Cold boot only occurs if the terminal is intentionally rebooted or if both the main
battery and the backup super-capacitor become fully discharged.
The first-time software load, as the name suggests, only happens once, at the fac-
tory, and is not discussed further here.
On a cold boot or resume from suspend, the peripheral controller boots using the
bootloader image in its flash.
Note: The following descriptions assume no errors during the boot process.
3.2.2.1 Cold Boot
During a cold boot, the peripheral controller is the first device powered up. It per-
forms the following steps:
1. Boots the bootloader image located in its own flash.
2. Turns on an LED to confirm the button press by the user.
3. Powers up the main processor but leaves it in reset.
4. Initializes the main processor.
5. Continues running its own software.
Once out of reset, the main processor performs the following tasks:
6. Initializes the 7535’s SDRAM and flash memory.
7. Loads its copy of the bootloader from the NAND flash into RAM.
8. Communicates back to the peripheral controller that everything is okay.
9. Jumps to the bootloader.