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Fan Speed Control with the EMC2102 Device
Revision 0.2 (09-17-07)
USER MANUAL SMSC EMC2102
26
5.6 Experiment 6 - Limits and Alerts
This experiment is designed to gain familiarity with the control registers for generating fan related
alarms and alerts associated with the EMC2102.
The CMF file for this experiment is EMC2102_default.cmf.
5.6.1 General Setup
For all these tests, the Fan Drive Setting register (51h), the TACH Target register (57h) and the TACH
Reading registers (58h) are selected to plot. As bits are switched in each of the tests, the register name
and address will be provided.
5.6.2 Fan Spin and Stall Interrupts
The Configuration/Status page in the ChipMan application contains all the Interrupt configuration and
status registers for the fan. In this experiment, the Fan Stall and Fan Spin status bits will be checked.
In order to see the status bits change, the Interrupt Status 2 register (23h) is plotted along with other
registers listed above. The Interrupt Mask register (24h) should be set to 10h (default) for this set of
experiments.
Start the plotting function within ChipMan, and force the fan to stop spinning. This will induce a Fan
Stall condition. The plot of the Status Register will show a peak of 1 count for the stall condition,
followed by peaks of 2 counts for each time the spin-up routine is invoked, as shown in Figure 5.22,
"Fan Spin and Stall". In order to see the spikes mentioned above, the max scale on the register 27h
plot needs to be modified. To do this, simply double click the 255 at the top of the "Y" axis, type a
different maximum value (10) and enter. And then double click the 0 at the bottom of the "Y" axis, type
a minimum value and enter. The scale will be changed.