REV. C

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ADT7463

Table V. Voltage Reading Registers (Power-On Default = 0x00)

Register Address

R/W

Description

0x20

Read-Only

2.5 V Reading (8 MSBs of reading)

0x21

Read-Only

0x22

Read-Only

0x23

Read-Only

5 V Reading (8 MSBs of reading)

0x24

Read-Only

12 V Reading (8 MSBs of reading)

If the extended resolution bits of these readings are also being read, the extended resolution registers (Reg. 0x76, 0x77) should be read first. Once the extended

resolution registers get read, the associated MSB reading registers get frozen until read. Both the extended resolution registers and the MSB registers get frozen.

Table VI. Temperature Reading Registers (Power-On Default = 0x80)

Register Address

R/W

Description

0x25

Read-Only

Remote 1 Temperature Reading* (8 MSBs of reading)

0x26

Read-Only

Local Temperature Reading (8 MSBs of reading)

0x27

Read-Only

Remote 2 Temperature Reading* (8 MSBs of reading)

These temperature readings are in twos complement format.

*Note that a reading of 0x80 in a temperature reading register indicates a diode fault (open or short) on that channel. If the extended resolution bits of these readings

are also being read, the extended resolution registers (Reg. 0x76, 0x77) should be read first. Once the extended resolution registers get read, all associated MSB read-

ing registers get frozen until read. Both the extended resolution registers and the MSB registers get frozen.

Table VII. Fan Tachometer Reading Registers (Power-On Default = 0x00)

Register Address

R/W

Description

0x28

Read-Only

TACH1 Low Byte

0x29

Read-Only

TACH1 High Byte

0x2A

Read-Only

TACH2 Low Byte

0x2B

Read-Only

TACH2 High Byte

0x2C

Read-Only

TACH3 Low Byte

0x2D

Read-Only

TACH3 High Byte

0x2E

Read-Only

TACH4 Low Byte

0x2F

Read-Only

TACH4 High Byte

These registers count the number of 11.11

µs periods (based on an internal 90 kHz clock) that occur between a number of consecutive fan TACH pulses (default = 2).

The number of TACH pulses used to count can be changed using the fan pulses per revolution register (Reg. 0x7B). This allows the fan speed to be accurately mea-

sured. Since a valid fan tachometer reading requires that two bytes are read, the low byte MUST be read first. Both the low and high bytes are then frozen until read.

At power-on, these registers contain 0x0000 until such time as the first valid fan TACH measurement is read in to these registers. This prevents false interrupts from

occurring while the fans are spinning up.

A count of 0xFFFF indicates that a fan is:

1. Stalled or blocked (object jamming the fan).

2. Failed (internal circuitry destroyed).

3. Not populated (the ADT7463 expects to see a fan connected to

each TACH. If a fan is not connected to that TACH, its TACH

minimum high and low byte should be set to 0xFFFF).

4. Alternate function, e.g., TACH4 reconfigured as THERM pin.

5. 2-Wire Instead of 3-Wire Fan.

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