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TMP451-Q1

SLOS877B – OCTOBER 2014 – REVISED JUNE 2019

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7.6.1.3 Status Register

The status register reports the state of the temperature ADC, the temperature limit comparators, and the

connection to the remote sensor. Table 5 lists the status register bits. The status register is read-only, and is

read by accessing pointer address 02h.

(1)

These flags stay high until the status register is read or they are reset by a POR when pin 6 is

configured as ALERT. Only bit 2 (OPEN) stays high until the status register is read or it is reset by a

POR when pin 6 is configured as THERM2.

Table 5. Status Register Format

STATUS REGISTER (READ = 02h, WRITE = N/A)

BIT NUMBER

BIT NAME

FUNCTION

7

BUSY

= 1 when the ADC is converting

6

= 1 when the local high temperature limit is tripped

5

= 1 when the local low temperature limit is tripped

4

= 1 when the remote high temperature limit is tripped

3

= 1 when the remote low temperature limit is tripped

2

= 1 when the remote sensor is an open circuit

1

RTHRM

= 1 when the remote THERM limit is tripped

0

LTHRM

= 1 when the local THERM limit is tripped

The BUSY bit = 1 if the ADC is making a conversion. This bit is set to 0 if the ADC is not converting.

The LHIGH and LLOW bits indicate a local sensor overtemperature or undertemperature event, respectively. The

RHIGH and RLOW bits indicate a remote sensor overtemperature or undertemperature event, respectively. The

OPEN bit indicates an open circuit condition on the remote sensor. When pin 6 is configured as the ALERT

output, the five flags are NORed together. If any of the five flags are high, the ALERT interrupt latch is set and

the ALERT output goes low. Reading the status register clears the five flags, provided that the condition that

caused the setting of the flags is not present anymore (that is, the value of the corresponding result register is

within the limits, or the remote sensor is connected properly and functional). The ALERT interrupt latch (and the

ALERT pin correspondingly) is not reset by reading the status register. The reset is done by the master reading

the temperature sensor device address to service the interrupt, and only if the flags have been reset and the

condition that caused them to be set is not present.

The RTHRM and LTHRM flags are set when the corresponding temperature exceeds the programmed THERM

limit. They are reset automatically when the temperature returns to within the limits. The THERM output goes low

in the case of overtemperature on either the local or the remote channel, and goes high as soon as the

measurements are within the limits again. The THERM hysteresis register (21h) allows hysteresis to be added so

that the flag resets and the output goes high when the temperature returns to or goes below the limit value minus

the hysteresis value.

When pin 6 is configured as THERM2, only the high limits matter. The LHIGH and RHIGH flags are set if the

respective temperatures exceed the limit values, and the pin goes low to indicate the event. The LLOW and

RLOW flags have no effect on THERM2, and the output behaves the same way when configured as THERM.