TMP139AIYAHT datasheet(13/58 Pages) TI

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7.3.7 Packet Error Check

The packet error check (PEC) is implemented at a CRC-8 with the polynomial given in Table 7-3.

Table 7-3. PEC Rule Table

PEC Rule

Attributes

PEC width

8-bits

PEC polynomial

X8 + X2 + X1 + 1

Initial seed value

00h

Input data reflected

Output data reflected

XOR value

00h

The PEC is supported in I3C mode only and is computed on the device address, the R/W bit and the data

packet. The seed value for the PEC function is reset to zero on either a Start or Repeated Start bus condition.

Any host transaction that results from a PEC enable or disable must be followed by a Stop condition on the bus

immediately to allow an update on the PEC control bit in the MR18 register.

7.4 Device Functional Modes

This section describes the serial address structure of the TMP139 and how the device operates in both I2C

mode and I3C basic mode, including the switching between the modes. This section also describes the behavior

of the TMP139 during IBI and the bus reset sequence.

7.4.1 Conversion Mode

The TMP139 powers up in continuous conversion mode. In this mode, the device shall perform temperature

conversions every 125 ms as shown in Figure 7-5.

Acti ve conversion time

Conversion interval

(tCONV)

Conversion interval

Start of co nve rsio n

(tACT)

Figure 7-5. Continuous Conversion Timing Diagram

The application software can stop the conversion by clearing bit 0 of the MR26 register. When disabled, the

device shall not update the result registers. When the temperature sensor is disabled, the host must wait for at

least one active conversion cycle for the disable to take effect before any other writes are performed to the

device. When the temperature sensor is re-enabled for continuous conversion mode, the host must wait for at

least one conversion interval before reading the temperature results. During this time, read to other registers

may be performed.

7.4.2 Serial Address

The TMP139 has a 7-bit serial address which is used by the host to communicate with the device in both I2C and

I3C basic modes of operation. The Table 7-4 shows the serial address format for the TMP139. As described in

the power-up sequence, the SA pin is sampled on power up. The sampled value of the SA pin is used to select

one of the two possible local device type ID (LID) section of the serial address. The LID is concatenated with the

host ID (HID) to form the 7-bit unique serial address.

Table 7-4. Serial Address Format

BIT 7

BIT 6

BIT 5

BIT 4

BIT 3

BIT 2

BIT 1

BIT 0

R/W

Local Device Type ID (LID)

Host ID (HID)

Read/Write

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TMP139

SNIS217 – DECEMBER 2020

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