result is ready before the previous result has been read, the new results overwrites the previous result and the Error Function 2

flag (ERF2) for the Voltage-Only function in the Device Status register is set (indicating an overrun event). Reading the

Voltage-Only Measurement Readout register clears also the ERF2 flag.

Readout Resolution

The resolution of the readout register is defined in the Voltage Capabilities register. The resolution of the

LM40 is fixed and cannot be modified by software. The voltage readout format is common to all voltage sensors and is 9-bits

unsigned. For over or under input voltage conditions the data is guaranteed to saturate at all "1"s or "0"s so long as Operating

Ratings of the LM40 are adhered to.

Function Event

The Voltage-Only Measurement function generates a Function Event to the master whenever a conversion

cycle is completed and new data is stored in the Readout register. When the new data is stored into the Readout register the SF2

bit in the Device Status register is set to 1 and remains set, until it is cleared by reading the Readout register. An Attention Request

is generated on the bus, only if it is enabled by the Attention Enable bit (ATE) in the Control register.

Setup Before Enabling

No setup is required for the Voltage-Only Measurement function before it is enabled.

2.10.2 Voltage Capabilities (Addr: 010 000; 10h)

Reg

Add

Register

Name

R/

W

P

O

R

Val

Bit

15

MSb

Bit

14

Bit

13

Bit

12

Bit

11

Bit

10

Bit

9

Bit

8

Bit

7

Bit

6

Bit

5

Bit

4

Bit

3

Bit

2

Bit

1

Bit

0

LSb

010 000

Voltage

Capabilities

R 0051h

Reserved

# of Voltage Sensors

Rout

Size

9-bit Resolution

0000000001010001

This register defines the format of the voltage data in the voltage readout register. The LM40 only supports one format for all

voltage measurements as defined by the values of this register.

Bit

Type

Description

2-0

RO

Resolution. This field defines the total number of significant bits in the Voltage Readout field in the Readout

register for this function. The voltage data is always aligned to the left in the Voltage Readout filed and is

extended with zeros.

001: 9-bit (value for the LM40, for other field values see the SensorPath specification)

3RO

RoutSize (Readout Register size). Defines the total size of the Readout register.

0: 16 bits. (value for the LM40 for other field values see the SensorPath specification)

8-4

RO

# of Voltage Sensors (Number of Voltage Sensors). Specifies the number of Voltage Sensors supported

by this function.

5: The number of Voltage Sensors. (value for the LM40 for other field values see the SensorPath

specification)

15-9

RO

Reserved. Will always read "0".

2.10.3 Voltage Readout (Addr: 010 001; 11h)

Reg

Add

Register

Name

R/

W

P

O

R

Val

Bit

15

MSb

Bit

14

Bit

13

Bit

12

Bit

11

Bit

10

Bit

9

Bit

8

Bit

7

Bit

6

Bit

5

Bit

4

Bit

3

Bit

2

Bit

1

Bit

0

LSb

010 001

Voltage

Readout

R

Voltage Readout

Reserved

SNUM

Reserved

MSb

LSb

0

0

0

0

Bit

Type

Description

0-1

RO

Reserved. Will always read "0".

4-2

RO

SNUM (Sensor Number). This field indicates the number of the current Voltage Sensor, to which the data in

the Voltage Readout field belongs. See Table Analog Input Voltage Mapping for assignments.

6-5

RO

Reserved. Will always read "0".

15-7

RO

Voltage Readout. This field holds the result of the voltage measurement. The active size of this field for the

LM40 is 9-bits, left justified. See Table Analog Input Voltage Mapping for voltage mapping details.

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