System information

2 CHARM Architecture

RS232 connector The RS232 connector provides access to the operating system of the

card.

EZ-Host USB Controller The USB controller is used to emulated peripheral devices to

the host computer. It is explained with more detail in section 5.1.2.

Flash Memory The ﬂash memory is the sole nonvolatile memory of the CHARM. It

contains the kernel of the embedded system, the root ﬁle system and a conﬁguration ﬁle for

the FPGA.

Reset Button This button resets the board units and reboots the system.

JTAG Connector The card is programmed with the aid of the JTAG connector. It is

directly connected to the Excalibur chip which provides write access to the ﬂash memory.

Therefore, the ﬂash memory can be written via the JTAG interface.

Internal USB Connector To reduce cabling at the backside of the computer, the CHARM

contains onboard USB connectors. The USB cable connects the CHARM board directly

with the computer’s main-board (if the main-board supports internal USB connections).

Connectors to the Optocoupler Optocouplers are used for the galvanically separation

of electric circuits. The CHARM uses optocoupler for the power and reset switch of the

mainboard. The power control of the host system is explained in section 5.3.

WOL Connector Wake On LAN (WOL) connector provides a standard interface for a

standby power source. Some mainboards are equipped with a WOL connector which is

used by network cards. With the aid of the WOL connection, the network card remains

powered if the host system is going to be switched oﬀ. Additionally, the network card can

power on the computer via the WOL connection.

General I/O Pins These pins are not used for a special purpose. They can be used for later

requirements, like an input for the chassis power button or a connection to the mainboard

CMOS reset switch, for example.

ADC The onboard analog-digital converter measures the PCI voltage and the temperature.

The usage of the ADC is explained in section 6.2.3.

Floppy Connector Since the CHARM emulates an USB mass storage device, the ﬂoppy

connector for ﬂoppy drive emulation is not used.

Sensor Connector Temperature and additional voltage sensors are connected to the

sensor connector. The PCI voltage is measured onboard and does not require an external

sensor.