LM64 datasheet(26/42 Pages) TI2

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ADDRESS

Hex

Read/

Write

Bits

POR

Value

Name

Description

R/W

7:0

0xFF

Tachometer

Limit (MSB)

These registers contain the current 16-bit Tachometer Count,

representing the period of time between tach pulses. Fan RPM

= (f * 5,400,000) / (Tachometer Count), where f = 1 for 2 pulses/rev

fan; f = 2 for 1 pulse/rev fan; and f = 2/3 for 3 pulses/rev fan. See

the Application Notes section for more tachometer information.

Note that the 16-bit tachometer MSB and LSB are reversed from

the 16 bit temperature readings.

R/W

7:2

0xFF

Tachometer

Limit (LSB)

R/W

1:0

[Reserved]

Not Used.

7.1.4.4 Local Temperature And Local High Setpoint Registers

ADDRES

Hex

Read/

Write

Bits

POR

Value

Name

Description

00HEX LOCAL TEMPERATURE REGISTER (8-bits)

Read

Only

7:0

N/A

Local Temperature Reading (8-bit)

8-bit temperature of the LM64.

05 (0B)HEX LOCAL HIGH SETPOINT REGISTER (8-bits)

R/W

7:0

0x46

(70°)

Local HIGH Setpoint

High Setpoint for the internal diode.

7.1.4.5 Remote Diode Temperature, Offset And Setpoint Registers

ADDRESS

Hex

Read/

Write

Bits

POR

Value

Name

Description

Read

Only

7:0

N/A

Remote Diode

Temperature

Reading (MSB)

This is the MSB of the LM64 remote diode temperature value, 2’s complement. Bit

7 is the sign bit, bit 6 has a weight 64°C, and bit 0 has a weight of 1°C. Read this

byte first. The actual remote diode temperature is 16°C higher than the values in

registers 0x01 and 0x10.

Read

Only

7:5

N/A

Remote Diode

Temperature

Reading (LSB)

This is the LSB of the LM64 remote diode temperature value, in 2’s complement.

Bit 7 has a weight 0.5°C, bit 6 has a weight of 0.25°C, and bit 5 has a weight of

0.125°C. The actual remote diode temperature is 16°C higher than the values in

registers 0x01 and 0x10.

4:0

Always 00.

R/W

7:5

Remote

Temperature

OFFSET (MSB)

These registers contain the offset value added to, or subtracted from, the remote

diode’s reading to compensate for the different non-ideality factors of different

processors, diodes, etc. The 2’s complement value, in these registers is added

to the output of the LM64’s ADC to form the temperature reading contained in

registers 01 and 10.

R/W

7:5

Remote

Temperature

OFFSET (LSB)

4:0

Always 00.

07 (0D)

R/W

7:0

0x46

(70°C)

Remote HIGH

Setpoint (MSB)

High setpoint temperature for remote diode. Same format as Remote

Temperature Reading (registers 01 and 10).

R/W

7:5

Remote HIGH

Setpoint (LSB)

4:0

Always 00.

08 (0E)

R/W

7:0

(0°C)

Remote LOW

Setpoint (MSB)

Low setpoint temperature for remote diode. Same format as Remote

Temperature Reading (registers 01 and 10).

R/W

7:5

Remote LOW

Setpoint (LSB)

4:0

Always 00.

R/W

7:0

0x55

(85°C)

Remote Diode

T_CRIT Limit

This 8-bit integer storing the T_CRIT limit is initially 85°C (101°C actual remote

T_Crit limit). This value can be changed at any time after power-up.

R/W

7:0

0x0A

(10°C)

Remote Diode

T_CRIT

Hysteresis

8-bit integer storing T_CRIT hysteresis. T_CRIT stays activated until the remote

diode temperature goes below [(T_CRIT Limit)—(T_CRIT Hysteresis)].

LM64

SNAS207B – MAY 2004 – REVISED JANUARY 2024

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