adt7476a Analog Devices, Inc., adt7476a Datasheet - Page 24

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

ADT7476A
For applications where the monitoring cycle time is important,
it can easily be calculated.
The total number of channels measured is
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As mentioned previously, the ADC performs round robin
conversions and takes 11 ms for each voltage measurement,
12 ms for a local temperature reading, and 39 ms for each
remote temperature reading. The total monitoring cycle time
for averaged voltage and temperature monitoring is, therefore,
nominally
Fan TACH measurements are made in parallel and are not
synchronized with the analog measurements in any way.
STATUS REGISTERS
The results of limit comparisons are stored in Interrupt Status
Register 1 and Interrupt Status Register 2. The status register bit
for each channel reflects the status of the last measurement and
limit comparison on that channel. If a measurement is within
limits, the corresponding status register bit is cleared to 0. If the
measurement is out-of-limits, the corresponding status register
bit is set to 1.
The state of the various measurement channels can be polled by
reading the status registers over the serial bus. In Bit 7 (OOL) of
Interrupt Status Register 1 (0x41), 1 means an out-of-limit event
has been flagged in Interrupt Status Register 2. This means the
user also needs to read Interrupt Status Register 2. Alternatively,
Pin 10 or Pin 14 can be configured as an SMBALERT output.
This hard interrupt automatically notifies the system supervisor
of an out-of-limit condition. Reading the status registers clears
the appropriate status bit as long as the error condition that
caused the interrupt has cleared. Status register bits are sticky.
Whenever a status bit is set, indicating an out-of-limit
condition, it remains set even if the event that caused it has
gone away (until read).
The only way to clear the status bit is to read the status register
after the event has gone away. Interrupt mask registers (0x74
and 0x75) allow individual interrupt sources to be masked from
causing an SMBALERT . However, if one of these masked
interrupt sources goes out of limit, its associated status bit is set
in the status registers.
Four dedicated supply voltage inputs
Supply voltage (V
Local temperature
Two remote temperatures
(5 × 11) + 12 + (2 × 39) =145 ms
CC
pin)
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Interrupt Status Register 1 (0x41)
Bit 7 (OOL) = 1, denotes a bit in Interrupt Status Register 2 is
set and Interrupt Status Register 2 should be read.
Bit 6 (R2T) = 1, Remote 2 temperature high or low limit has
been exceeded.
Bit 5 (LT) = 1, Local temperature high or low limit has been
exceeded.
Bit 4 (R1T) = 1, Remote 1 temperature high or low limit has
been exceeded.
Bit 3 (5 V) = 1, 5 V high or low limit has been exceeded.
Bit 2 (V
Bit 1 (V
Bit 0 (2.5 V) = 1, 2.5 V high or low limit has been exceeded. If
the 2.5 V input is configured as THERM , this bit represents the
status of THERM .
Interrupt Status Register 2 (0x42)
Bit 7 (D2) = 1, indicates an open or short on D2+/D2– inputs.
Bit 6 (D1) = 1, indicates an open or short on D1+/D1– inputs.
Bit 5 (F4P) = 1, indicates Fan 4 has dropped below minimum
speed. Alternatively, indicates that the THERM limit has been
exceeded, if the THERM function is used. Alternatively,
indicates the status of GPIO6.
Bit 4 (FAN3) = 1, indicates Fan 3 has dropped below
minimum speed.
Bit 3 (FAN2) = 1, indicates Fan 2 has dropped below
minimum speed.
Bit 2 (FAN1) = 1, indicates Fan 1 has dropped below
minimum speed.
Bit 1 (OVT) = 1, indicates a THERM overtemperature limit has
been exceeded.
Bit 0 (12V/VC) = 1, indicates a 12 V high or low limit has been
exceeded. If the VID code change function is used, this bit
indicates a change in VID code on the VID0 to VID4 inputs.
SMBALERT Interrupt Behavior
The ADT7476A can be polled for status, or an SMBALERT
interrupt can be generated for out-of-limit conditions. It is
important to note how the SMBALERT output and status
bits behave when writing interrupt handler software.
CC
CCP
) = 1, V
) = 1, V
CC
CCP
high or low limit has been exceeded.
high or low limit has been exceeded.