Real Time Clock - Eurotech Apollo User Manual

APOLLO user manual
For connector details, see page 34.
For details about the USB bus, or to determine whether particular peripherals are
available, please go to www.usb.org.
A USB power switch provides power to the USB ports during normal operation and also
during standby (S3) and soft off (S5).
A USB power control switch is used to control the power and protect against short circuit
conditions. This can be enabled/disabled by the processor and the USB function needs
to be enabled in the BIOS to ensure that power is supplied to each device. The USB
function is controlled using the I/O Device Configuration screen within the setup utility -
see page 62
If the USB voltage is short circuited or more than 500mA is drawn from either supply the
switch turns off the power supply and automatically protects the device and board. The
VBUS signal is derived from the ATX +5V supply via the APOLLO.

Real Time Clock

The Real Time Clock (RTC) module provides a battery backed-up date and time-keeping
device. It has two banks of static RAM with 128 bytes each (although the first bank has
114 bytes for general purpose usage). Three interrupt features are available:
•
Time of day alarm with once a second to once a month range.
•
Periodic rates of 122µs to 500ms.
•
End of update cycle notification.
Seconds, minutes, hours, days, day of week, month and year are counted. Daylight
savings compensation is optional. The hour is represented in twelve or twenty-four hour
format, and data can be represented in BCD or binary format. The design is functionally
compatible with the Motorola MC146818B. The time keeping comes from a 32.768 kHz
oscillating source, which is divided to achieve an update every second.
Tamper detection
A tamper detection input is included within the real time clock circuitry on the ICH4 that
operates in all power modes. The status of the tamper detection bit is battery backed in
static RAM. To use the tamper detection, a normally open switch should be used; a
tamper is detected when the switch contacts close.
The BIOS Security setup screen (see page 81) provides two options for enabling a case
open warning. It also provides a secure chassis mode that requires the supervisor
password to be entered and the chassis intrusion detection to be disabled before the
board will boot to an operating system. Both options are disabled by default.
104
for details.
Issue G