LM73 datasheet(15/18 Pages) NSC

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2.0 LM73 Registers (Continued)

2.5 T

LOW LOWER-LIMIT REGISTER

Pointer Address 03h (R/W)

Reset State: 8000h (–256˚C)

D15

D14

D13

D12

D11

D10

SIGN

128˚C

64˚C

32˚C

16˚C

8˚C

4˚C

2˚C

1˚C

0.5˚C

0.25˚C

reserved

Bits

Name

Description

15:5

Lower-Limit

Temperature

If the measured temperature that is stored in the temperature register falls below this

user-programmable lower temperature limit, the ALERT pin will be deactivated and the T

LOW

flag in the Control/Status register will be set to 1. Two’s complement format.

4:0

Reserved

Returns zeros upon read. Recommend writing zeros only in these bits.

2.6 CONTROL/STATUS REGISTER

Pointer Address 04h (R/W)

Reset State: 08h

TO_DIS

RES1

RES0

reserved

ALRT_STAT

THI

TLOW

DAV

Bits

Name

Description

Time-Out Disable

Disable the time-out feature on the SMBDAT and SMBCLK lines if set to 1. Setting this bit

turns off the bus-idle timers, enabling the LM73 to operate at lowest shutdown current.

6:5

Temperature

Resolution

Selects one of four user-programmable temperature data resolutions

00: 0.25˚C/LSB, 11-bit word (10 bits plus sign)

01: 0.125˚C/LSB, 12-bit word (11 bits plus sign)

10: 0.0625˚C/LSB, 13-bit word (12 bits plus sign)

11: 0.03125˚C/LSB, 14-bit word (13 bits plus sign)

reserved

Always returns zero when read. Recommend customer write zero only.

ALERT Pin Status

Value is 0 when ALERT output is low. Value is 1 when ALERT output is high. The ALERT

output is reset under any of the following conditions: (1) Cleared by writinga1tothe ALERT

Reset bit in the configuration register, (2) Measured temperature falls below the T

LOW limit,

or (3) cleared via the ARA sequence. Recommend customer write zero only.

Temperature High

Flag

Bit is set to 1 when the measured temperature exceeds the T

HIGH limit stored in the

programmable T

HIGH register. Flag is reset to 0 when both of the following conditions are

met: (1) measured temperature no longer exceeds the programmed T

HIGH limit and (2) upon

reading the Control/Status register. If the temperature is not longer above the T

HIGH limit, this

status bit remains set until it is read by the master so that the system can check the history

of what caused the ALERT output to go active. This bit is not cleared after every read if the

measured temperature is still above the T

HIGH limit.

Temperature Low

Flag

Bit is set to 1 when the measured temperature falls below the T

LOW limit stored in the

programmable T

LOW register. Flag is reset to 0 when both of the following conditions are

met: (1) measured temperature is no longer below the programmed T

LOW limit and (2) upon

reading the Control/Status register. If the temperature is no longer below the T

LOW limit, the

status bit remains set until it is read by the master so that the system can check the history

of what cause the ALERT output to go active. This bit is not cleared after every read if

temperature is still below T

LOW limit.

Data Available Flag

This bit is 0 when the LM73 is in the process of converting a new temperature. It is 1 when

the conversion is done. After initiating a temperature conversion while operating in the

one-shot mode, this status bit can be monitored to indicate when the conversion is done.

After triggering the one-shot conversion, the data in the temperature register is invalid until

this bit is high (that is, after completion of the conversion). On power-up, the LM73 is in

continuous conversion mode; while in continuous conversion mode (the default mode after

power-on reset) this bit will always be high. Recommend customer write zero only.

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