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2.7
Basic Operation and Main Panel Functions
As previously stated, clicking on the “Get All Values” button updates all value and limit displays on the
main panel. Additional features of the main panel include:
•
Clicking in any white “Value” box causes the latest data to be displayed for that box.
•
Clicking on any “Change” button allows the associated upper or lower limit to be changed.
•
The “+2.5V”, “Vcc 3.3V”, and “FAN” buttons allow the alternate functions for those inputs to be
selected directly from the front panel. The main panel display is reformatted and the appropriate mode
bit in the Channel Mode Register is set or cleared. When “FAN” mode is selected, pull-down menus
are available to set the internal clock divisor used for each FAN counter channel.
•
The “Loop” buttons in the Temperature Measurement section cause the software to read and display
updated temperature values approximately every second. This data can be logged to a text file is
desired.
•
Separate “Read” buttons are provided to read the latest interrupt status and mask register settings. Note
that reading the status registers clears the status bits for certain channels.
•
Individual interrupt mask bits can be set by clicking in the appropriate check box.
•
A separate “Reset” button is provided to reset the external CI (Chassis Intrusion) circuit. An opaque
cover must be placed over the light sensor before initiating the reset operation. After the Reset, two
reads of the Interrupt Status register #2 can be performed to confirm that the Chassis Intrusion circuit
has been reset.
•
The Alarm Outputs section displays the status of the Int# output and provides a button to test the “Alert
Response” feature of the LM87. The Int# jumper must be installed on the evaluation board to allowing
monitoring of the Int# output. During the Alert Response test, the Enable Alert Response bit in
Register 80h is set, and then an SMBus read at the Alert Response Address is performed. If the Int#
output is active, the LM87 will reply to the Alert Response read. *Note: The Alert Response test will
fail if the Int# is not active and/or enabled.
2.8
Additional Information
The Help menu provides access to the LM87 datasheet, this manual, and a schematic of the evaluation
board. Please refer to the LM87 datasheet for detailed information on device operation.
2.9
Troubleshooting and Common Problems
There are several common problems that can occur when using the LM87 Evaluation board.
1.
The most common error message seen is “SMB Acknowledge Error” which indicates that the LM87 is
not responding with an acknowledge when expected. The most common causes of this error are:
•
No power applied to LM87 device. This can be caused by missing jumpers, poor connection
between the evaluation board and parallel port, or the incorrect parallel port address setting. Check
all of these possible causes and try again.
•
Wrong SMBus address setting. Check the address jumpers and the SMBus address setting.
2.
Another common error is “Fatal Error: Bus Not Recovering – SDA low”. The most common cause is
an incorrect parallel port address setting. If the wrong parallel port address is set, power and
communications will not be directed to the port that the LM87 Evaluation board is on. Set the address
to the proper value, and try again.