REV. 0

ADM1020

–7–

The power-on default value of the Address Pointer Register is

00h, so if a read operation is performed immediately after power-

on, without first writing to the address pointer, the value of the

local temperature will be returned, since its register address is

00h.

Value Registers

The ADM1020 has two registers to store the results of local and

remote temperature measurements. These registers are written

to by the ADC and can only be read over the SMBus.

Status Register

Bit 7 of the Status Register indicates that the ADC is busy con-

verting when it is high. Bits 5 to 3 are flags that indicate the

results of the limit comparisons.

If the local and/or remote temperature measurement is above

the corresponding high temperature limit or below the corre-

sponding low temperature limit, then one or more of these flags

will be 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 will be

set and the

ALERT output will go low. Reading the Status

Register will clear the five flag bits, provided the error condi-

tions 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.

The

ALERT interrupt latch is not reset by reading the Status

Register, but will be reset when the

ALERT output has been

serviced by the master reading the device address, provided the

error condition has gone away and the Status Register flag bits

have been reset.

Table II. 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

1–0

Reserved

*These flags stay high until the Status Register is read or they are reset by POR.

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.

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.

Table III. List of Registers

Read Address (Hex)

Write Address (Hex)

Name

Power-On Default

Not Applicable

Not Applicable

Address Pointer

Undefined

00

Not Applicable

Local Temperature Value

0000 0000

(00h)

01

Not Applicable

Remote Temperature Value

0000 0000

(00h)

02

Not Applicable

Status

Undefined

03

09

Configuration

0000 0000

(00h)

04

0A

Conversion Rate

0000 0010

(02h)

05

0B

Local Temperature High Limit

0111 1111

(7Fh) (127

°C)

06

0C

Local Temperature Low Limit

1100 1001

(C9h) (–55

°C)

07

0D

Remote Temperature High Limit

0111 1111

(7Fh) (127

°C)

08

0E

Remote Temperature Low Limit

1100 1001

(C9h) (–55

°C)

Not Applicable

0F

One-Shot

See Note 1

10

Not Applicable

Reserved

Undefined (Note 2)

11

13

Reserved

Undefined (Note 2)

12

14

Reserved

Undefined (Note 2)

15

16

Reserved

1000 0000 (Note 2)

17

18

Reserved

Undefined (Note 2)

19

Not Applicable

Reserved

0000 0000 (Note 2)

20

21

Reserved

Undefined

FE

Not Applicable

Manufacturer ID

0100 0001

(41h)

FF

Not Applicable

Die Revision Code

Undefined

NOTES