ADT7473 Analog Devices, Inc., ADT7473 Datasheet - Page 20

• Manufacturer Part Number: ADT7473
• Description: Dbcool Remote Thermal Monitor And Fan Controller
• Manufacturer: Analog Devices, Inc.

ADT7473
LIMITS, STATUS REGISTERS, AND INTERR
LIMIT VALUES
Associated with each measurement channel on the ADT74
are high and low limits. These can form the basis of system
status monitoring; a status bit can be set for any out-of-limit
condition and is 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 th
Voltage Limit Registers
Register 0x46, V
Register 0x47, V
Register 0x48, V
Register 0x49, V High Limit = 0xFF default
Temperature Limit Registers
Register 0x4E, Remote 1 Temperature Low Limit = 0x01 defau
Register 0x4F, Remote 1 Temperature High Limit = 0xFF default
Register 0x6A, Remote 1 THERM Limit = 0xA4 default
Register 0x50, Local Temperature Low Limit = 0x01 default
Register 0x51, Local Temperature High Limit = 0xFF default
Register 0x6B, Local THERM Temperature Limit = 0xA4 default
Register 0x52, Remote 2 Temperature Low Limit = 0x01 default
Register 0x53, Remote 2 Temperature High Limit = 0xFF def
Register 0x6C, Remote 2
default
THERM Limit Register
Register 0x7A, THERM Timer Limit = 0x00 default
16-Bit Limits
The fan TACH measurements are 16-bit results. The fan TAC
limits are also 16
Because fans running under speed or stalled are normally th
only conditions of interest, only high limits exist for fan TAC
Because th
exceeding the limit indicates a slow or stalled fan.
e fan TACH period is actually being measured,
CCP
CCP
CC
CC
bits, consisting of a high byte and low byte.
Low Limit = 0x00 default
Low Limit = 0x00 default
High Limit = 0xFF default
THERM Temperature Limit = 0xA4
e ADT7473.
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Fan Limit Registers
Register 0x54, TACH1 Minimum Low Byte = 0xFF default
Register 0x55, TACH1 Minimum High Byte = 0xFF def
Register 0x56, TACH2 Minimum Low Byte = 0xFF defa
Register 0x57, TACH2 Minimum High Byte = 0xFF defau
Register 0x58, TACH3 Minim
Register 0x59, TACH3 Minimum High Byte = 0xFF defau
Register 0x5A, TACH4 Minimum Low Byte = 0xFF default
Register 0x5B, TACH4 M
Out-of-Limit Comparisons
Once all limits h
enabled for moni
temperature measurements in roun
appropriate status bit for out-of-limit conditions. TACH
measurements are not part of this round-robin cycle. Comp
sons are done differently depending on whether the measured
value is being compared to a high or low limit.
High limit > comparison performed
Low limit ≤ comparison performed
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 (0x40). By default,
the ADT7473 p
each analog in
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
taken to monitor all the analog inputs is normally not of
interest, because the most recently measured value of any input
can be read out at any time.
For applications where the monitoring cycle time is important,
it can easily be calculated. The total number of channels
measured is
•
•
•
•
One dedicated supply voltage input (V
Supply voltage (V
Local temperature
Two remote temperatures
put in turn and, as each measuremen
owers up with this bit set. The ADC
ave been programmed, the ADT7473 can be
toring. The ADT7473 measures all voltage and
CC
pin)
inimum High Byte = 0xFF default
um Low Byte = 0xFF default
d-robin format and sets the
CCP
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