ADT7467 Analog Devices, Inc., ADT7467 Datasheet - Page 21

• Manufacturer Part Number: ADT7467
• Description: Dbcool Remote Thermal Monitor And Fan Controller
• Manufacturer: Analog Devices, Inc.

LIMITS, STATUS REGISTERS, AND INTERRUPTS
LIMIT VALUES
High and low limits are associated with each measurement
channel on the ADT7467. These limits form the basis of
system-status monitoring in that a status bit can be set for any
out-of-limit condition and detected by polling the device.
Alternatively, SMBALERT interrupts can be generated to flag a
processor or microcontroller of out-of-limit conditions.
8-Bit Limits
The following is a list of 8-bit limits on the ADT7467.
Voltage Limit Registers
Reg. 0x46 V
Reg. 0x47 V
Reg. 0x48 V
Reg. 0x49 V
Temperature Limit Registers
Reg. 0x4E Remote 1 temperature low limit = 0x01 default
Reg. 0x4F Remote 1 temperature high limit = 0x7F default
Reg. 0x6A Remote 1 THERM limit = 0x64 default
Reg. 0x50 local temperature low limit = 0x01 default
Reg. 0x51 local temperature high limit = 0x7F default
Reg. 0x6B local THERM limit = 0x64 default
Reg. 0x52 Remote 2 temperature low limit = 0x01 default
Reg. 0x53 Remote 2 temperature high limit = 0x7F default
Reg. 0x6C Remote 2 THERM limit = 0x64 default
THERM Limit Register
Reg. 0x7A THERM limit = 0x00 default
16-Bit Limits
The fan TACH measurements are 16-bit results. The fan TACH
limits are also 16 bits, consisting of a high byte and low byte.
Because slow or stalled fans are normally the only conditions of
interest, only high limits exist for fan TACHs. Because the fan
TACH period is measured, exceeding the limit indicates a slow
or stalled fan.
Fan Limit Registers
Reg. 0x54 TACH1 minimum low byte = 0x00 default
Reg. 0x55 TACH1 minimum high byte = 0x00 default
Reg. 0x56 TACH2 minimum low byte = 0x00 default
CCP
CCP
CC
CC
low limit = 0x00 default
high limit = 0xFF default
low limit = 0x00 default
high limit = 0xFF default
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Reg. 0x57 TACH2 minimum high byte = 0x00 default
Reg. 0x58 TACH3 minimum low byte = 0x00 default
Reg. 0x59 TACH3 minimum high byte = 0x00 default
Reg. 0x5A TACH4 minimum low byte = 0x00 default
Reg. 0x5B TACH4 minimum high byte = 0x00 default
Out-of-Limit Comparisons
Once all limits are programmed, the ADT7467 can be enabled
for monitoring. The ADT7467 measures all voltage and
temperature measurements in round-robin format and sets the
appropriate status bit for out-of-limit conditions. TACH
measurements are not part of this round-robin cycle. Compari-
sons are done differently, depending on whether the measured
value is being compared to a high or low limit.
Voltage and temperature channels use a window comparator for
error detecting and, therefore, have high and low limits. Fan
speed measurements use only a low limit. This fan limit is
needed only in manual fan control mode.
Analog Monitoring Cycle Time
The analog monitoring cycle begins when a 1 is written to the
start bit (Bit 0) of Configuration Register 1 (Reg. 0x40). By
default, the ADT7463 powers up with this bit set. The ADC
measures each analog input in turn and, as each measurement is
completed, the result is automatically stored in the appropriate
value register. This round-robin monitoring cycle continues
unless disabled by writing a 0 to Bit 0 of Configuration
Register 1.
As the ADC is normally left to free-run in this manner, the time
to monitor all analog inputs is normally not of interest, because
the most recently measured value of an input can be read at any
time.
For applications where the monitoring cycle time is important,
it can be calculated easily. The total number of channels
measured is
•
•
•
•
As mentioned previously, the ADC performs round-robin
conversions. The total monitoring cycle time for averaged
High limit: > comparison performed
Low limit: ≤ comparison performed
One dedicated supply voltage input (V
Supply voltage (V
Local temperature
Two remote temperatures
CC
pin)
CCP
)
ADT7467