14.1 Introduction

The WINC SPI Protocol is implemented as a command-response transaction and assumes one party is the Host and the other is the Client. The roles correspond to the Host and Client devices on the SPI bus. Each message has an identifier in the first byte indicating the type of message:

• Command
• Response
• Data

In the case of Command and Data messages, the last byte is used as data integrity check.

The format of Command and Response and Data frames are described in the following sections. The following points apply:

• There is a response for each command.
• Transmitted/received data is divided into packets with fixed size.
• For a WR transaction (Client is receiving data packets), the Client sends a response for each data packet.
• For a RD transaction (Host is receiving data packets), the Host does not send a response. If there is an error, the Host requests a retransmission on the lost data packet.
• Protection of commands and data packets by CRC is optional.