Framing

This section outlines the general frame format used by all sub-protocols.

The protocol handler ID field identifies which sub-protocol to decode the packet by, and then which command handler to forward the packet to.

In general, ID == 0x00 is used as a “query” function in order for the host to “discover” the feature set of the tool.

Table 1. Command Frame Format
Field Size Value
SOF 1 byte 0x0E
Protocol version 1 byte 0x00 in this version (all packets)
Sequence ID 2 bytes Incrementing from 0x00 (least significant byte sent first)
Protocol handler ID 1 byte Destination sub-protocol handler ID
Payload N bytes Data
Table 2. Response Frame Format
Field Size Value
SOF 1 byte 0x0E
Sequence ID 2 bytes Echo of incoming ID (least significant byte sent first)
Protocol handler ID 1 byte Source sub-protocol handler ID
Payload N bytes Data
Table 3. Event Frame Format
Field Size Value
SOF 1 byte 0x0E
Protocol version 1 byte 0x00 in this version (all packets)
Sequence ID 2 bytes Incrementing from 0x00 (least significant byte sent first)
Protocol handler ID 1 byte Source sub-protocol handler ID
Payload N bytes Data

The protocol handler ID field identifies which sub-protocol to decode the packet by, and then which command handler to forward the packet to.

In general, ID == 0x00 is used as a “query” function in order for the host to “discover” the feature set of the tool.

If there is a condition where the EDBG AVR command handler expects more data for a command than is available, then the next incoming command will be rejected and an error response (RSP_FAILED with failure code FAILURE_USB_PREVIOUS_UNDERRUN) will be returned . Note that such an underrun situation will result in unknown values for the parameters of the failing command and the host will have to do the necessary cleanup to undo any undesired behavior. The underrun error reporting is done by transport layer and is independent of the sub-protocol being used.

Note: Unless otherwise stated, all multi-byte fields in this section are sent with least significant byte first.