ADT7468 Analog Devices, Inc., ADT7468 Datasheet - Page 23

• Manufacturer Part Number: ADT7468
• Description: Dbcool Remote Thermal Controller And Voltage Monitor
• Manufacturer: Analog Devices, Inc.

Since the ADC normally runs freely in this manner, the time
taken to monitor all the analog inputs is usually not of interest,
because the most recently measured value of any input can be
read at any time.
For applications where the monitoring cycle time is important,
it can be calculated easily.
The measured channels are
•
•
•
•
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 Status Registers 1
and 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-limit,
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
Status Register 1 (Reg. 0x41), 1 means that an out-of-limit event
has been flagged in Status Register 2. This means that the user
also needs to read 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 appro-
priate status bit as long as the error condition that caused the
interrupt has cleared. Status register bits are sticky. The status
bits are referred to as sticky, because they remain set until read
by software. Whenever a status bit is set, indicating an out-of-
limit condition, it remains set even if the event that caused it
has ceased (until read). The only way to clear the status bit is to
read the status register after the event has ceased. Interrupt
status mask registers (0x74, and 0x75) allow individual inter-
rupt sources to be masked from causing an SMBALERT . How-
ever, if one of these masked interrupt sources goes out-of-limit,
its associated status bit is set in the interrupt status registers.
Four dedicated supply voltage inputs
Supply voltage (V
Local temperature
Two remote temperatures
(5 × 11) + 12 + (2 × 39) = 145 ms
CC
pin)
Rev. A | Page 23 of 84
Status Register 1 (Reg. 0x41)
Bit 7 (OOL) = 1, denotes a bit in Status Register 2 is set and
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.
Status Register 2 (Reg. 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.
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 VID5 inputs.
INTERRUPTS
SMBALERT Interrupt Behavior
The ADT7468 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.
ADT7468