Case M1: Address Packet Transmit Complete - Direction Bit Set to ‘0’

If a client device responds to the address packet with an ACK, the Write Interrupt Flag (WIF) is set to ‘1’, the Received Acknowledge (RXACK) flag is set to ‘0’, and the Clock Hold (CLKHOLD) flag is set to ‘1’. The WIF, RXACK and CLKHOLD flags are located in the Host Status (TWIn.MSTATUS) register.

The clock hold is active at this point, forcing the SCL low, which will stretch the low period of the clock to slow down the overall clock frequency, forcing delays required to process the data and preventing further activity on the bus.