User`s manual

32 Functional Description
Reset
A reset will be generated by the following conditions:
X Pressing the front panel reset button
X Watchdog overflow
X CompactPCI backplane PRST# input (CompactPCI con-
nector J2, pin C17)
SMBus Devices
The cPCI-3920 provides a System Management Bus (SMBus)
for access to several system monitoring and configuration
functions. The SMBus consists of a two-wire I2C bus interface.
The following table describes the function and address of every
onboard SMBus device.
Table 3-2: SMBus Devices and Addresses
Thermal Management / System Monitoring
The W83792AG can be used to monitor several critical hardware
parameters of the system, including power supply voltages and
temperatures, all of which are very important for the proper opera-
tion and stability of a high-end computer system.
The voltages +12 V, +5 V, +3.3 V, and Vcore are supervised. The
temperature sensors monitor the CPU temperature and the ambi-
ent temperature to ensure that the system is operating at a safe
temperature level. If the CPU temperature is too high, the sensor
automatically reduces the CPU clock frequency, depending on the
mode chosen in the BIOS settings.
Device SMBus Address
Clock Buffer DCh
Clock Generator D2h
SPD A0h
EEPROM (Board VPD) AEh