REV. C

ADT7463

–49–

Table XXXVI. Register 0x78 – Configuration Register 3 (Power-On Default = 0x00)

Bit

Name

R/W*

Description

<0>

ALERT

Read/Write

ALERT = 1, Pin 10 (PWM2/SMBALERT) is configured as an SMBALERT interrupt

output to indicate out-of-limit error conditions.

<1>

THERM

Read/Write

THERM Enable = 1 enables THERM monitoring functionality on the pin

Enable

determined by Bit 1 (TH5V) of Configuration Register 4. When THERM is

asserted, fans can be run at full speed or a timer can be triggered to time how long

THERM has been asserted for.

<2>

BOOST

Read/Write

BOOST = 1, assertion of THERM causes all fans to run at 100% duty cycle for

fail-safe cooling.

<3>

FAST

Read/Write

FAST = 1 enables fast TACH measurements on all channels. This increases the

TACH measurement rate from once per second, to once every 250 ms (4�).

<4>

DC1

Read/Write

DC1 = 1 enables TACH measurements to be continuously made on TACH1.

<5>

DC2

Read/Write

DC2 = 2 enables TACH measurements to be continuously made on TACH2.

<6>

DC3

Read/Write

DC3 = 1 enables TACH measurements to be continuously made on TACH3.

<7>

DC4

Read/Write

DC4 = 1 enables TACH measurements to be continuously made on TACH4.

*This register becomes read-only when the Configuration Register 1 Lock bit is set to 1. Any further attempts to write to this register will have no effect.

Table XXXVII. Register 0x79 – THERM Status Register (Power-On Default = 0x00)

Bit

Name

R/W

Description

<7:1>

TMR

Read-Only

Times how long THERM input is asserted. These seven bits read zero until the

THERM assertion time exceeds 45.52 ms.

<0>

ASRT/TMR0 Read-Only

Gets set high on the assertion of the THERM input. Cleared on read. If the THERM

assertion time exceeds 45.52 ms, this bit gets set and becomes the LSB of the 8-bit TMR

reading. This allows THERM assertion times from 45.52 ms to 5.82 s to be reported

back with a resolution of 22.76 ms.

Table XXXVIII. Register 0x7A – THERM Limit Register (Power-On Default = 0x00)

Bit

Name

R/W

Description

<7:0>

LIMT

Read/Write

Sets maximum THERM assertion length allowed, before an interrupt is generated. This

is an 8-bit limit with a resolution of 22.76 ms allowing THERM assertion limits of 45.52 ms

to 5.82 s to be programmed. If the THERM assertion time exceeds this limit, Bit 5 (F4P)

of Interrupt Status Register 2 (Reg 0x42) is set. If the limit value is 0x00, then an

interrupt is generated immediately on the assertion of the THERM input.

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