adt7476a Analog Devices, Inc., adt7476a Datasheet - Page 23

• Manufacturer Part Number: adt7476a
• Description: Dbcool Remote Thermal Controller And Voltage Monitor
• Manufacturer: Analog Devices, Inc.

LIMITS, STATUS REGISTERS, AND INTERRUPTS
LIMIT VALUES
Associated with each measurement channel on the ADT7476A
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 out-of-limit
conditions to a processor or microcontroller.
8-Bit Limits
The following is a list of 8-bit limits on the ADT7476A.
Voltage Limit Registers
Register 0x44, 2.5 V Low Limit = 0x00 default
Register 0x45, 2.5 V High Limit = 0xFF default
Register 0x46, V
Register 0x47, V
Register 0x48, V
Register 0x49, V
Register 0x4A, 5 V Low Limit = 0x00 default
Register 0x4B, 5 V High Limit = 0xFF default
Register 0x4C, 12 V Low Limit = 0x00 default
Register 0x4D, 12 V High Limit = 0xFF default
Temperature Limit Registers
Register 0x4E, Remote 1 Temperature Low Limit = 0x81 default
Register 0x4F, Remote 1 Temperature High Limit = 0x7F default
Register 0x6A, Remote 1 THERM Limit = 0x64 default
Register 0x50, Local Temperature Low Limit = 0x81 default
Register 0x51, Local Temperature High Limit = 0x7F default
Register 0x6B, Local THERM Limit = 0x64 default
Register 0x52, Remote 2 Temperature Low Limit = 0x81 default
Register 0x53, Remote 2 Temperature High Limit = 0x7F default
Register 0x6C, Remote 2 THERM Limit = 0x64 default
THERM Timer Limit Register
Register 0x7A, THERM Timer Limit = 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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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 fans running under speed or stalled are normally the
only conditions of interest, only high limits exist for fan TACHs.
Because the fan TACH period is actually being measured,
exceeding the limit indicates a slow or stalled fan.
Fan Limit Registers
Register 0x54, TACH1 Minimum Low Byte = 0xFF default
Register 0x55, TACH1 Minimum High Byte = 0xFF default
Register 0x56, TACH2 Minimum Low Byte = 0xFF default
Register 0x57, TACH2 Minimum High Byte = 0xFF default
Register 0x58, TACH3 Minimum Low Byte = 0xFF default
Register 0x59, TACH3 Minimum High Byte = 0xFF default
Register 0x5A, TACH4 Minimum Low Byte = 0xFF default
Register 0x5B, TACH4 Minimum High Byte = 0xFF default
Out-of-Limit Comparisons
Once all limits have been programmed, the ADT7476A can be
enabled for monitoring. The ADT7476A 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 (0x40). 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 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.
High Limit: > Comparison Performed
Low Limit: ≤ Comparison Performed
ADT7476A