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STATUS REGISTER

CONFIGURATION REGISTER 1

CONFIGURATION REGISTER 2

TMP421

TMP422

TMP423

SBOS398B – JULY 2007 – REVISED MARCH 2008

The temperature range is set by configuring the

RANGE bit (bit 2) of the Configuration Register.

The

Status

Register

reports

the

state

of

the

Setting this bit low configures the TMP421/22/23 for

temperature ADCs. Table 4 summarizes the Status

the standard measurement range (–40

°C to +127°C);

Register bits. The Status Register is read-only, and is

temperature

conversions

will

be

stored

in

the

read by accessing pointer address 08h.

standard binary format. Setting bit 2 high configures

the TMP421/22/23 for the extended measurement

The BUSY bit = '1' if the ADC is making a conversion;

range (–55

°C to +150°C); temperature conversions

it is set to '0' if the ADC is not converting.

will be stored in the extended binary format (see

Table 1).

The remaining bits of the Configuration Register are

Configuration Register 1 (pointer address 09h) sets

reserved and must always be set to '0'. The power-on

the temperature range and controls the shutdown

reset value for this register is 00h.

mode. The Configuration Register is set by writing to

pointer address 09h and read by reading from pointer

address 09h. Table 5 summarizes the bits of

Configuration Register 1.

Configuration

Register

2

(pointer

address

0Ah)

controls which temperature measurement channels

The shutdown (SD) bit (bit 6) enables or disables the

are enabled and whether the external channels have

temperature measurement circuitry. If SD = '0', the

the resistance correction feature enabled or not.

TMP421/22/23 convert continuously at the rate set in

Table

6

summarizes

the

bits

of

Configuration

the conversion rate register. When SD is set to '1',

Register 2.

the TMP421/22/23 stop converting when the current

conversion sequence is complete and

enter

a

shutdown mode. When SD is set to '0' again, the

TMP421/22/23

resume

continuous

conversions.

When SD = '1', a single conversion can be started by

writing to the One-Shot Register. See the One-Shot

Conversion section for more information.

Table 4. Status Register Format

STATUS REGISTER (Read = 08h, Write = NA)

BIT #

D7

D6

D5

D4

D3

D2

D1

D0

BIT NAME

BUSY

0

0

0

0

0

0

0

POR VALUE

0

0

0

0

0

0

0

(1)

FOR TMP421/TMP423: The BUSY changes to '1' almost immediately (< 100

µs) following power-up, as the TMP421/TMP423 begin the

first temperature conversion. It is high whenever the TMP421/TMP423 convert a temperature reading.

FOR TMP422: The BUSY bit changes to '1' approximately 1ms following power-up. It is high whenever the TMP422 converts a

temperature reading.

Table 5. Configuration Register 1 Bit Descriptions

CONFIGURATION REGISTER 1 (Read/Write = 09h, POR = 00h)

POWER-ON RESET

BIT

NAME

FUNCTION

VALUE

7

Reserved

—

0

0 = Run

6

SD

0

1 = Shut Down

5, 4, 3

Reserved

—

0

0 = –55

°C to +127°C

2

Temperature Range

0

1 = –55

°C to +150°C

1, 0

Reserved

—

0

Copyright © 2007–2008, Texas Instruments Incorporated

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