CP307
Functional Description
ID 34424, Rev. 3.0
Page 2 - 9
P R E L I M I N A R Y
2.2.4
Reset
The CP307 is automatically reset by a precision voltage monitoring circuit that detects a drop
in voltage below the acceptable operating limit of 4.45 V for the 5 V line and below 2.8 V for the
3.3 V line. Other reset sources include the watchdog timer and the local push-button switch
(only on 8HP). The CP307 responds to any of these sources by initializing local peripherals.
A reset will be generated by the following conditions:
• +5 V supply falls below 4.45 V (typ.)
• +3.3 V supply falls below 2.8 V (typ.)
• Pushbutton "RESET" pressed (only on 8HP)
• Watchdog overflow
• CompactPCI backplane PRST# input (CompactPCI connector J2, pin C17)
2.2.5
SMBus Devices
The CP307 provides a System Management Bus (SMBus) for access to several system
monitoring and configuration functions. The SMBus consists of a two-wire I
²
C bus interface.
The following table describes the function and address of every onboard SMBus device.
2.2.6
Thermal Management/System Monitoring
The Super I/O SCH3112 can be used to monitor several critical hardware parameters of the
system, including power supply voltages, fan speeds and temperatures, all of which are very
important for the proper operation and stability of a high-end computer system. The SCH3112
provides an LPC bus interface.
The vo12 V, +5 V, +3.3 V, +2.5 V, and Vcore are supervised. One fan tachometer
output can be measured using the SCH3112's FAN1 input. One pulse width modulation
(PWM1) output can be used for FAN speed control.
The temperature sensors on the SCH3112 monitor the CPU temperature and the ambient
temperature around the SCH3112 to ensure that the system is operating at a safe temperature
level.
Note ...
The Intel 82801GR chipset provides an enhanced reset control logic. The
reset pulse width is typical 5 ms (min. 1 ms) regardless of how long the
RESET pushbutton is being pressed or the PRST signal remains active.
Table 2-5: SMBus Device Addresses
DEVICE
SMBUS ADDRESS
EEPROM 24LC64
1010111xb
Clock
1101001xb
SPD (soldered DDR2)
1010000xb
SPD (SODIMM DDR2)
1010010xb
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