**Not mandatory.** Only needed if a VSCP boot-loader algorithm is used.

Data for a block of memory. This event has no meaning for any node that is not in boot mode and should be disregarded.

 | Data byte | Description | 
 | :---------: | ----------- | 
 | 0         | Data.       | 
 | 1         | Data.       | 
 | 2         | Data.       | 
 | 3         | Data.       | 
 | 4         | Data.       | 
 | 5         | Data.       | 
 | 6         | Data.       | 
 | 7         | Data.       | 

A [CLASS1.PROTOCOL, Type=50 (Block Data ACK)](./class1.protocol.md#type50)
is sent as a response for each event received.

A [CLASS1.PROTOCOL, Type=51 (Block Data NACK)](./class1.protocol.md#type51)
is sent on failure.

**Note** If the block to fill is not a multiple of eight the receiving node should handle and discard any excess data. This is true also if more block data frames are received than the block can hold.

**Level II** The size of the block is level II max data (512 bytes) or a smaller block or a mix of both.
