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User Guide XB1 COM Express Module
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Local SMB Devices
The XB1 COM Express Module contains a few devices that are attached to the System Management
Bus (SMBus). These are the clock generation chip, the SPD EEPROMs on the SO-DIMM memory
modules, a general purpose serial EEPROM and a supply voltage and CPU temperature controlling
device in particular. Other devices could be connected to the SMB on the carrier board across J-COM
A-B.
Address Description
0x58 Hardware Monitor/CPU Temperature Sensor (LM87)
0xA0 SPD of SODIMM1
0xA2 SPD of SODIMM2
0xAE General Purpose EEPROM
0xD2 Main Clock Generation (CK-410M)
Hardware Monitor LM87
The XB1 COM Express Module is provided with a LM87 hardware monitor attached to the SMB. This
device is capable to observe board and CPU temperatures as well as several supply voltages generated
on the board with a resolution of 8 bit. The following table shows the mapping of the voltage inputs
of the LM87 to the corresponding supply voltages of the XB1 COM Express Module:
Input Source Resolution
[mV]
Register
AIN1 CPU Core Voltage 9.8 0x28
AIN2 +1.05V 9.8 0x29
VCCP1 +1.5V 14.1 0x21
VCCP2/D2- +1.8V 14.1 0x25
+2.5V/D2+ +2.5V 13 0x20
+3.3V +3.3V 17.2 0x22
+5V +5V 26 0x23
+12V +12V 62.5 0x24
Besides the continuous measuring of temperatures and voltages the LM87 may compare these values
against programmable upper and lower boundaries. As soon as a measurement violates the allowed
value range, the LM87 may request an interrupt via the GPI[7] of the ICH6.