5.2 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.
| 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 |
| 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 |
| 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.