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AS621x

Register Description

Datasheet

• PUBLIC

DS000677

• v4-00 • 2022-May-17

36

│ 26

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.

6.3.10

General Call

A general call is issued by the master by transmitting the general call address (000 0000) with a low

R/W bit. When this command is issued on the bus, the device acknowledges this command. The

device also acknowledges the second byte but ignores the data. Subsequent bytes sent by the master

during the general call are not acknowledged.

6.3.11

Start Byte

When the master transmits address 000 0000 and

a high R/W bit (“START byte”) the device

acknowledges the address. The device then send the MSB data byte and LSB data byte, where the

data corresponds to the content of the register whose address has been last written to. After reset this

corresponds to the temperature register.

6.3.12

Timeout Function

The serial interface of the slave device is reset if the clock signal SCL is kept low for typ. 30 ms. Such

a condition results in a release of the data line by the slave in case it has been pulled to low level. The

slave remains inactive after a timeout and waits for a new START command invoked by the bus

master. In order to prevent a timeout, the bus transfer rate must be higher than 1 kHz.

6.3.13

Bus Conditions

The following conditions occur on the serial bus which is compatible to the I²C-Bus.

Bus Idle

The signals SDA and SCL are not actively driven and pulled to a high level by an external pull-up

resistor.