TMP1827 datasheet(27/65 Pages) TI

27 / 65 page

9.4.2.2 Comparator Mode

The device operates in comparator mode, when the ALERT_MODE is set as '1b'. In the alert mode of operation,

the alert status flag and IO2/ALERT pin are asserted when the last temperature conversion is either higher than

the temperature alert high limit or when it is lower than the temperature alert low limit register.

The alert status flag and IO2/ALERT pin are deasserted only when the result of the last temperature conversion

is less than the temperature alert high limit minus the hysteresis or above the temperature low limit plus the

hysteresis as shown in Figure 9-18. The hysteresis is selectable using the HYSTERESIS bit field in the device

configuration-2 register.

ALERT_HIGH

ALERT_LOW

Temperature

Temperature conversions

ALERT_HIGH

ALERT_LOW

Alert Status Read

ALERT pin

ALERT_LOW+HYSTERESIS

ALERT_HIGH-HYSTERESIS

Figure 9-18. Comparator Mode Timing Diagram

9.4.3 1-Wire Interface Communication

To leverage the features effectively, the device access consists of three distinct phases. As shown in Figure

9-19, any bus communication starts with a bus reset condition to which every device on the bus must respond.

This is followed by a highly configurable address phase, where the host selects the device it wants to access.

Finally, there is a function phase where the host provides the selected device(s) the action it wants to take.

Reset

Command

Device Address

Func on

Write Data

Bus Reset Phase

Address Phase

Func on Phase

Answer to

Reset

Read Data

CRC

Figure 9-19. 1-Wire Bus Communication

In a 1-Wire bus, all write and reads are initiated by the host except for the answer to reset which is initiated by

the devices on the bus.

9.4.3.1 Bus Reset Phase

The bus reset phase is the beginning of the communication. The phase is initiated by the host by holding the

1-Wire data line low for a period tRSTL. All devices on the bus, irrespective of their current state shall respond

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TMP1827

SBOSA15A – SEPTEMBER 2022 – REVISED MAY 2023

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