System information

3 Software of the CHARM

The CHARM is an embedded system with a hard-core CPU, main memory and a non

volatile storage. The operating system of the card is Linux which is started by ARMboot,

the boot-loader of the CHARM. The following sections describe the booting procedure, the

Linux system and the ﬁle system of the card.

3.1 Boot Loader

ARMboot [43] is the boot-loader of the CHARM. It is available as free software under the

GNU Public License (GPL). The boot-loader is stored on the ﬂash ﬁle system and activated

after power up. It is run directly from the ﬂash memory by using the Altera Run-From-Flash

mode [44]. Thereby, ARMboot is started from the Altera boot loader which initializes the

Excalibur Stripe and the memory map [45]. Additionally, the Altera boot-loader conﬁgures

the FPGA logic via an integrated AHB slave peripheral [46]. The content of the FPGA

logic is stored in the ﬂash memory. Afterwards, ARMboot copies the Linux kernel to the

RAM and starts the system. It supports three kinds of booting the system: boot from

memory, boot via tftp [47] and boot using the BOOTP [48] protocol. Figure 3.1 depicts

the boot sequence of the CHARM.

3.2 Operating System

The CHARM uses the standard Linux kernel 2.4.21 [49]. The kernel is compiled for the ARM

922T architecture. The related conﬁguration ﬁles are located in the Linux kernel source

directory arch/arm/mach-epxa10db. The compiled kernel is stored in the ﬂash memory in

a zlib

compressed data format. It will decompress itself at boot time.

3.2.1 Device Drivers

Within the scope of this thesis, Linux device drivers were developed which gain access to

the CHARM hardware functions. Table 3.1 gives an overview of CHARM related device

drivers. The following paragraphs explain the usage of some of the device drivers.

adc The ADC driver communicates with the ADC via an SPI interface. Access to the

ADC device ﬁles triggers a readout to the ADC.

A software library used for data compression.