29.3.2.3.1.1 Case S1: Address Packet Accepted - Direction Bit Set to ‘0’

If an ACK is sent by the client after the address packet is received, and the Read/Write Direction (DIR) bit in the Client Status (TWIn.SSTATUS) register is set to ‘0’, the host indicates a write operation.

The clock hold is active at this point, forcing the SCL low and stretching 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.