LM63 datasheet(20/28 Pages) NSC

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2.0 LM63 Registers (Continued)

Tachometer Count And Limit Registers

ADDRESS

Hex

Read/

Write

Bits

POR

Value

Name

Description

HEX TACHOMETER COUNT (MSB) and 46HEX TACHOMETER COUNT (LSB) REGISTERS (16 bits: Read LSB first to lock

MSB and ensure MSB and LSB are from the same reading)

Read

Only

7:0

N/A

Tachometer

Count (MSB)

These registers contain the current 16-bit Tachometer Count, representing

the period of time between tach pulses.

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

16-bit temperature readings.

Read

Only

7:2

N/A

Tachometer

Count (LSB)

Read

Only

1:0

Tachometer

Edge Count

Bits

Edges Used

Tach_Count_Multiple

00:

Reserved - do not use

01:

10:

11:

Note: If PWM_Clock_Select = 360 kHz, then Tach_Count_Multiple = 1

regardless of the setting of these bits.

HEX TACHOMETER LIMIT (MSB) and 48HEX TACHOMETER LIMIT (LSB) REGISTERS

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 Applications 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.

Local Temperature And Local High Setpoint Registers

ADDRESS

Hex

Read/

Write

Bits

POR

Value

Name

Description

HEX LOCAL TEMPERATURE REGISTER (8-bits)

Read

Only

7:0

N/A

Local

Temperature

Reading (8-bit)

8-bit integer representing the temperature of the LM63 die.

05 (0B)

HEX LOCAL HIGH SETPOINT REGISTER (8-bits)

R/W

7:0

0x46

(70˚)

Local HIGH

Setpoint

High Setpoint for the internal diode.

LM63 Datasheet(PDF) 20 Page - National Semiconductor (TI)

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