Hardware reference guide

7535 Hardware Reference Guide 29
Chapter 3: The Software
Overview Of The 7535’s Software
3.1 Overview Of The 7535’s Software
This chapter describes features of the boot process and operating-system software
that are specific to the 7535.
The 7535 uses a custom build of Microsoft’s Windows CE.NET 4.2, with OS-native
device drivers for its custom hardware. It can accept executables written for the Intel
X-Scale PXA255 processor, or (with the appropriate runtime engine) .NET CIL
executables or Java bytecode executables.
The Psion Teklogix-developed ‘BooSt’ bootloader and mini-OS is used to perform
initial hardware configuration and load system software.
The system software design supports the services required by applications. The
operating system environment and standard development tools provide the standard
services; an application may interface with Psion Teklogix’ custom hardware and
software interfaces via the Psion Teklogix Mobile Devices SDK.
3.2 The Boot Process
3.2.1 Overview
The 7535 handheld terminal has both a main processor and a peripheral controller.
When the terminal is booted, the peripheral controller boots into BooSt, then runs its
own software. This software is stored in the peripheral controller’s onboard flash
memory.
The main processor uses BooSt as a bootloader and Windows CE .NET 4.2 as the
primary operating system.
The image for the main processor’s software, including BooSt and Windows CE
.NET, are stored in the terminal’s flash memory. The main processor cannot boot
directly from the flash; a more complex boot process is required. The peripheral
controller loads a small amount of code into the main processor’s instruction cache,
enabling it to start its own boot loader.
3.2.2 Boot Types
The boot process is the series of steps between pressing the on key on the 7535 to
when the main operating system is ready for user input. There are three possible
times that this may happen: