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Intel
®
IQ31244 Customer Reference Board
20 User’s Manual
3.4 SDRAM EEPROM
The EEPROM located on the SDRAM module contains identification and configuration
information. Start-up code must read this information on power-up and must properly configure the
Intel XScale
®
processor to the SDRAM type.
3.5 Temperature Sensors
The National Semiconductor* LM75 temperature sensors have over-temperature trip points that
trigger an interrupt when crossed. The sensors are placed on the board at U8 and U35. They share
an interrupt line to the processor. Polling the two devices is required to determine which device
triggered the interrupt. The sensors are placed in interrupt mode by the Breeze* initialization code
(for more information, see the National Semiconductor website at http://www.national.com). The
default over-temperature point is 80 °C. The sensors can be read for a temperature reading at any
time. Reading after an interrupt clears the interrupt. The sensor does not interrupt again until the
temperature drops below the hysteresis value (default is 75 °C) and rises again beyond the trip
point. Consult the LM75 datasheet for more details on programming the temperature sensors.
3.6 Reset Supervisor
The STMicroelectronics* M41ST85W supervisor chip is connected to the Intel
®
80321 I/O
Processor through its I
2
C bus interface. The supervisor controller uses a 512-bit, static CMOS
SRAM organized as 64 words by 8 bits wide. This controller is driven by a 32.768 KHz clock. It
features the time-of-day clock/calendar function, status/control of alarm, watchdog timer, and
power-fail voltage monitoring (used by Ethernet LAN Power Good). The eight clock address
locations contain the century, year, month, date, day, hour, minute, second, and tenths/hundredths
of a second in 24-hour Binary Code Decimal (BCD) format. Corrections for 28-, 29- (leap year—
valid until year 2100), 30- and 31-day months are made automatically.
The supervisor chip is supplied with a SNAPHAT package, which has a crystal and a battery for
backup during power failures. The SNAPHAT comes in two battery sizes (48 or 120 mAh).