Current Duty

Value (Decimal)

Value (Hex)

.

.

.

.

.

.

.

.

.

50.196%

128

80h

.

.

.

.

.

.

.

.

.

100%

255

FFh

4.5 Register 3Eh: Company ID

Register

Address

Read/

Write

Register

Name

Bit 7

(MSB)

Bit 6

Bit 5

Bit 4

Bit 3

Bit 2

Bit 1

Bit 0

(LSB)

Default

Value

3Eh

R

Company ID

7

6543210

01h

The company ID register contains the company identification number. For National Semiconductor this is 01h. This number is

assigned by Intel and is a method for uniquely identifying the part manufacturer. This register is read only — a write to this

register has no effect.

4.6 Register 3Fh: Version/Stepping

Register

Address

Read/

Write

Register

Name

Bit 7

(MSB)

Bit 6

Bit 5

Bit 4

Bit 3

Bit 2

Bit 1

Bit 0

(LSB)

Default

Value

3Fh

R

Version/Stepping

VER3

VER2

VER1

VER0

STP3

STP2

STP1

STP0

60h

The four least significant bits of the Version/Stepping register [3.0] contain the current stepping of the LM85 silicon. The four most

significant bits [7.4] reflect the LM85 base device number when set to a value of 0110b. All LM85 revisions will have a base

number of 6. For the LM85C, this register will read 01100000b (60h). The LM85B will read 01100010b (62h).If new revisions of

the LM85C or LM85B are released the last 4 bits of this register will change.

The register is used by application software to identify which device in the hardware monitor family of ASICs has been

implemented in the given system. Based on this information, software can determine which registers to read from and write to.

Further, application software may use the current stepping to implement work-arounds for bugs found in a specific silicon

stepping.

This register is read only — a write to this register has no effect.

4.7 Register 40h: Ready/Lock/Start/Override

Register

Address

Read/

Write

Register

Name

Bit 7

(MSB)

Bit 6

Bit 5

Bit 4

Bit 3

Bit 2

Bit 1

Bit 0

(LSB)

Default

Value

40h

R/W

Ready/Lock/Start/Override

RES

RES

RES

RES

OVRID

READY

LOCK

START

00h

Bit

Name

R/W

Default

Description

0

START

R/W

0

When software writesa1to this bit, the LM85 fan monitoring and PWM output

control functions will use the values set in the fan control limit and parameter

registers (address 5Ch through 6Eh). Before this bit is set, the LM85 will not

update the used register values, the default values will remain in effect.

Whenever this bit is set to 0, the LM85 fan monitoring and PWM output control

functions use the default fan limits and parameters, regardless of the current

values in the limit and parameter registers (5C through 6Eh). The LM85 will

preserve the values currently stored in the limit and parameter registers when

this bit is set or cleared. This bit becomes read only when the

Ready/Lock/Start/Override register Lock bit is set.

It is expected that all limit and parameter registers will be set by BIOS or

application software prior to setting this bit.

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