ADM1021A

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9

corresponding low temperature limit, then one or more of

these flags are set. Bit 2 is a flag that is set if the remote

temperature sensor is open−circuit. These five flags are

NOR’d together so that if any of them are high, the ALERT

interrupt latch is set and the ALERT output goes low. Reading

the status register clears the five flag bits, provided the error

conditions that caused the flags to be set have gone away.

While a limit comparator is tripped due to a value register

containing an out−of−limit measurement, or the sensor is

open−circuit, the corresponding flag bit cannot be reset. A

flag bit can only be reset if the corresponding value register

contains an in−limit measurement, or the sensor is good.

Table 2. Status Register Bit Assignments

Bit

Name

Function

7

BUSY

1 when ADC converting

6

LHIGH*

1 when local high temp limit tripped

5

LLOW*

1 when local low temp limit tripped

4

RHIGH*

1 when remote high temp limit tripped

3

RLOW*

1 when remote low temp limit tripped

2

OPEN*

1 when remote sensor open−circuit

1 to 0

Reserved

*These flags stay high until the status register is read or they are

reset by POR.

Table 3. List of ADM1021A Registers

Read Address (Hex)

Write Address (Hex)

Name

Power−On Default

Not applicable

Not applicable

Address pointer

Undefined

00

Not applicable

Local temperature value

1000 0000 (0x80) (−128

°C)

01

Not applicable

Remote temperature value

1000 0000 (0x80) (−128

°C)

02

Not applicable

Status

Undefined

03

09

Configuration

0000 0000 (0x00)

04

0A

Conversion rate

0000 0010 (0x02)

05

0B

Local temperature high limit

0111 1111 (0x7F) (+127

°C)

06

0C

Local temperature low limit

1100 1001 (0xC9) (−55

°C)

07

0D

Remote temperature high limit

0111 1111 (0x7F) (+127

°C)

08

0E

Remote temperature low limit

1100 1001 (0xC9) (−55

°C)

Not applicable

0F (Note 1)

One−shot

10

Not applicable

Reserved

Reserved for future versions

11

11

Remote temperature offset

0000 0000 (0

°C)

12

12

Reserved

Reserved for future versions

13

13

Reserved

Reserved for future versions

14

14

Reserved

Reserved for future versions

15

16

Reserved

Reserved for future versions

17

18

Reserved

Reserved for future versions

19

Not applicable

Reserved

Reserved for future versions

20

21

Reserved

Reserved for future versions

FE

Not applicable

Manufacturer device ID

0100 0001 (0x41)

FF

Not applicable

Die revision code

0011 xxxx (0x3x)

1. Writing to Address 0F causes the ADM1021A to perform a single measurement. It is not a data register and data written to it is irrelevant.

The ALERT interrupt latch is not reset by reading the

status register, but is reset when the ALERT output is

serviced by the master reading the device address, provided

the error condition has gone away and the status register flag

bits have been reset.

Configuration Register

Two bits of the configuration register are used. If Bit 6 is 0,

which is the power−on default, the device is in operating

mode with the ADC converting. If Bit 6 is set to 1, the device

is in standby mode and the ADC does not convert. Standby

mode can also be selected by taking the STBY pin low. In

standby mode, the values stored in the remote and local

temperature registers remain at the values they were when

the part was placed in standby.

Bit 7 of the configuration register is used to mask the

ALERT output. If Bit 7 is 0, which is the power−on default,

the ALERT output is enabled. If Bit 7 is set to 1, the ALERT

output is disabled.