STCN75M2F datasheet(17/35 Pages) STMICROELECTRONICS

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STCN75

Functional description

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3.1.3

Temperature register

The temperature register is a two-byte (16-bit) “Read only” register (see Table 7). Digital

temperatures from the T-to-D converter are stored in the temperature register in two’s

complement format, and the contents of this register are updated each time the T-to-D

conversion is finished.

The user can read data from the temperature register at any time. When a T-to-D conversion

is completed, the new data is loaded into a comparator buffer to evaluate fault conditions

and will update the temperature register if a read cycle is not ongoing. If a READ is ongoing,

the previous temperature will be read. Accessing the STCN75 continuously without waiting

at least one conversion time between communications will prevent the device from updating

the temperature register with a new temperature conversion result. Consequently, the

STCN75 should not be accessed continuously with a wait time of less than tCONV (max).

All unused bits following the digital temperature will be zero. The MSB position of the

temperature register always contains the sign bit for the digital temperature, and bit 14

contains the temperature MSB. All bits in the temperature register default to zero at power-

up.

3.1.4

Over-limit temperature register (TOS)

TOS register is a two-byte (16-bit) READ/WRITE register that stores the user-programmable

upper trip-point temperature for the thermal alarm in two’s complement format (see Table 8

on page 18). This register defaults to 80°C at power-up (i.e., 0101 0000 0000 0000).

The format of the TOS register is identical to that of the temperature register. The MSB

position contains the sign bit for the digital temperature and Bit14 contains the temperature

MSB.

For 9-bit conversions, the trip-point temperature is defined by the 9 MSBs of the TOS

Table 7.

Temperature register format(1)

These are comparable formats to the LM75.

Bytes

HS byte

LS byte

Bits

MSB

TMSB

TLSB

LSB

STCN75

TD8

(S)

TD7

(TMSB)

TD0

(TLSB)

Keys: S = two’s complement sign bit

TMSB = temperature MSB

TLSB = temperature LSB

TDx = temperature data bits

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