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AS6221T

Register Description

Datasheet

• PUBLIC

DS001032

• v1-00 • 2022-Apr-08

37

│ 26

6.3.7

Slave Transmitter

The master transmits the slave address with a high R/W bit. In turn, the slave acknowledges a valid

slave address. Subsequently, the slave transmits the MSB byte of the actual selected data register by

the index register. After the MSB byte transmission, acknowledge is sent by the master. Afterwards,

the LSB byte is transmitted by the slave which is also acknowledged by the master after the

completed transmission. The data transfer can be terminated by the master by transmitting a Not-

Acknowledge after the transmitted slave data or by invoking a START or a STOP condition on the bus.

6.3.8

Alert Function

If the device is configured for an interrupt mode operation (IM=1), the ALERT output can be used as

an alert signal.

If the polarity bit is set to ‘0’ (POL=’0’), the alert condition bit is set to ‘0’ in case the temperature has

exceeded the configured value in register THIGH. Accordingly, the alert condition bit

is set to ‘1’ if the

temperature has fallen below the configured value in register TLOW.

If the polarity bit is set to ‘1’ (POL=’1’), the alert condition bit is inverted. The following table

summarizes the status of the alert condition bit with different alert conditions and polarity

configurations.

Figure 30:

Alert Condition Bit

Polarity Bit

Alert Condition

Alert Condition Bit (AC-Bit)

0

T ≥ THIGH

0

0

T ≤ TLOW

1

1

T ≥ THIGH

1

1

T ≤ TLOW

0

6.3.9

High Speed Mode

The bus operation is limited to 400 kHz unless a high speed command is issued by the master device

as the first byte after a START condition. This switches the bus to a high speed operation which allows

data transfer frequencies up to 3.4 MHz. Such a command is not acknowledged by the slave but the

input filter time constants on the serial interface (SDA and SCL) are adapted to allow the higher

transfer rate.

After a high speed command, the slave address is transmitted by the master in order to invoke a data

transfer. The bus keeps operating at the higher operating frequency until the master issues a STOP

condition on the serial bus. Upon the reception of the STOP condition by the slave, the input filters are

switched to their initial time constants which allow lower transfer rates only.