Fan Control Device with High Frequency PWM and Temperature Monitors
Datasheet
6.3.1
Continuous Monitoring Mode
In the continuous monitoring mode, the sampling and conversion process is performed continuously
for each voltage and temperature reading after the Start bit is set high. The time for each voltage and
temperature reading is shown above for each measurement option.
The continuous monitoring function is started by doing a write to the Ready/Lock/Start Register, setting
the Start bit (Bit 0) high. The part then performs a “round robin” sampling of the inputs, in the order
shown below (see Table 6.3). Sampling of all values occurs in a nominal 210ms (default - see
Table 6.2, “Conversion Cycle Timing,” on page 21).
Table 6.3 ADC Conversion Sequence
SAMPLING ORDER
REGISTER
1
2
3
4
5
Remote Diode Temp Reading 1
Ambient Temperature reading
VCC reading
Vccp (processor) reading
Remote Diode Temp Reading 2
When the continuous monitoring function is started, it cycles through each measurement in sequence,
and it continuously loops through the sequence approximately once every 210ms (default - see
Table 6.2, “Conversion Cycle Timing,” on page 21). Each measured value is compared to values stored
in the Limit registers. When the measured value violates the programmed limit the Hardware Monitor
Block will set a corresponding status bit in the Interrupt Status Registers.
If auto fan option is selected, the hardware will adjust the operation of the fans accordingly. See Auto
Fan Control Operating Mode on page 31.
The results of the sampling and conversions can be found in the Reading Registers and are available
at any time.
6.3.2
Cycle Monitoring Mode
In cycle monitoring mode, the part completes all sampling and conversions, then waits approximately
one second to repeat the process. It repeats the sampling and conversion process typically every 1.2
seconds (1.4 sec max - default averaging enabled). The sampling and conversion of each voltage and
temperature reading is performed once every monitoring cycle. This is a power saving mode.
The cycle monitoring function is started by doing a write to the Ready/Lock/Start Register, setting the
Start bit (Bit 0) high. The part then performs a “round robin” sampling of the inputs, in the order shown
above.
When the cycle monitoring function is started, it cycles through each measurement in sequence, and
it produces a converted voltage and temperature reading for each input. The state machine waits
approximately one second before repeating this process. Each measured value is compared to values
stored in the Limit registers. When the measured value violates (or is equal to) the programmed limit
the Hardware Monitor Block will set a corresponding status bit in the Interrupt Status Registers.
If auto fan option is selected, the hardware will adjust the operation of the fans accordingly. See the
section titled Auto Fan Control Operating Mode on page 31.
The results of each sampling and conversion can be found in the Reading Registers and are available
at any time, however, they are only updated once per conversion cycle.
Revision 0.2 (06-14-06)
SMSC EMC2300
DATA2S2HEET
SMSC [ SMSC CORPORATION ]
