Real-Time Clock, Universal Serial Bus USB

User Guide XB1 COM Express Module

Real-Time Clock

The XB1 COM Express Module has a time-of-day clock and 100-year calendar, integrated into the ICH6.

A battery on the board keeps the clock current when the computer is turned off. The XB1 uses a Vanadium-Pentoxide-Lithium rechargeable battery, giving an autonomy of more than 50 days when fully loaded after 24 hours. The cell is free of memory effects and withstands deep discharging. Under normal conditions, replacement should be superfluous during lifetime of the board. Custom specific versions of the XB1 may not provide the accumulator.

In addition, VCC_RTC is also redundantly derived from the carrier board (if supported). The time keeping autonomy period is then defined by the battery capacity accommodated on the carrier.

Universal Serial Bus (USB)

The XB1 COM Express Module is provided with eight USB ports, all of them are USB 2.0 capable. Four active-low over-current sensing inputs are available in addition, suitable for attachment of electronic switches such as the LM3526-L on the carrier board. The USB controllers are integrated into the ICH6.

LPC Super-I/O Interface

In a modern system, legacy ports as PS/2 keyboard/mouse, COM1/2 and LPT have been replaced by USB and Ethernet connectivity. The 1.4MB floppy disk drive has been swapped against CD/DVD-RW drives or USB memory sticks. Hence, the XB1 COM Express Module is virtually provided with all necessary I/O functionality. However, for BIOS and OS software compatibility, the XB1 is additionally equipped with a simple Super-I/O chip. The Super-I/O controller resides on the local LPC bus (LPC = Low Pin Count interface standard), which is a serialized ISA bus replacement. For debug only, a connector P-SIO may be stuffed on the XB1, with KB/MS signals derived from the SIO and also a rudimentary serial I/F (TTL-level Tx/Rx RTS/CTS).

The SIO provides a rich set of GPIO lines. Four channels are used as GPI0..3, and another 4 channels as GPO0..3, all routed to the connector J-COM A-B, for use on the carrier board.

Firmware Hub (Flash BIOS)

The BIOS is stored in an 8Mbit Firmware Hub attached to the LPC bus. The firmware hub contains a nonvolatile memory core based on flash technology, allowing the BIOS to be upgraded. The XB1 firmware hub may be deselected by the carrier board from use as primary BIOS source, by activating the signal BIOS_DISABLE# on J-COM A-B. This allows a potential secondary firmware hub residing on the carrier board to be used as alternative BIOS source.

The FWH can be reprogrammed (if suitable) by a DOS based tool. This program and the latest XB1 COM Express Module BIOS are available from the EKF website. Read carefully the enclosed instructions. If the programming procedure fails e.g. caused by a power interruption, the XB1 COM Express Module may no more be operable. In this case you would have to send in the board, because the BIOS is directly soldered to the PCB and cannot be changed by the user.

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