There are two communication endpoints. Endpoint 0 is used for the enumeration process. Endpoint 1 is a 64-byte Bulk OUT endpoint. Endpoint 2 is a 64-byte Bulk IN endpoint. SAM-BA Boot commands are sent by the host through endpoint 1. If required, the message is split by the host into several data payloads by the host driver.
If the command requires a response, the host can send IN transactions to pick up the response.