ATmega32HVB datasheet(164/273 Pages) ATMEL

164 / 273 page

164

8042A–AVR–07/09

ATmega16HVB/32HVB

27.5.5

Control Unit

The Control unit monitors the TWI bus and generates responses corresponding to settings in the

TWI Control Register (TWCR). When an event requiring the attention of the application occurs

on the TWI bus, the TWI Interrupt Flag (TWINT) is asserted. In the next clock cycle, the TWI Sta-

tus Register (TWSR) is updated with a status code identifying the event. The TWSR only

contains relevant status information when the TWI interrupt flag is asserted. At all other times,

the TWSR contains a special status code indicating that no relevant status information is avail-

able. As long as the TWINT flag is set, the SCL line is held low. This allows the application

software to complete its tasks before allowing the TWI transmission to continue.

The TWINT flag is set in the following situations:

• After the TWI has transmitted a START/REPEATED START condition.

• After the TWI has transmitted SLA+R/W.

• After the TWI has transmitted an address byte.

• After the TWI has lost arbitration.

• After the TWI has been addressed by own slave address or general call.

• After the TWI has received a data byte.

• After a STOP or REPEATED START has been received while still addressed as a Slave.

• When a bus error has occurred due to an illegal START or STOP condition.

ATmega32HVB 데이터시트(PDF) 164 Page - ATMEL Corporation