Select In Broadcast Mode (W) command
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Description (see command description format info here)
This command is used to pre-select a certain DS for subsequent firmware upload. Only few NetLoader commands (such as Echo (X)) are accepted when sent in broadcast UDP datagrams. All other commands are only accepted if they address a specific DS. Such specific addressing normally involves sending UDP datagrams with the IP-address of the targeted DS as the destination (i.e. non-broadcast datagrams). This requires the IP-address of the DS to be reachable.
Select In Broadcast Mode command provides a way around this. Target DS, referenced by its MAC-address, is first pre-selected using this command. After that, all broadcast commands that are normally ignored when sent as broadcasts, are not ignored and processed by this pre-selected DS.
When Select In Broadcast Mode command is issued all devices whose MAC-addresses do not match the target MAC-address supplied in the command body de-select themselves. This means that to switch onto working with another DS in the broadcast mode you need to send the new Select In Broadcast Mode command with the new target MAC-address. This will pre-select a different DS while at the same time de-selecting the DS that was selected before. To de-select all DS on the network send Select In Broadcast Mode command with no MAC-address field.
This command only influences which DS responds when it is addressed using broadcast UDP commands. Command has no influence over commands sent using normal IP addressing.
The only possible reply to this command is OK (A). It is issued by the DS that has recognised its MAC-address in the command body. If no DS on the local network recognizes its MAC then there will be no reply received to this command.
Select In Broadcast Mode command should be issued (when necessary) right after the NetLoader is started as all subsequent commands, such as Start Over (Q), Data Block (D), and Verify And Start Firmware (E) won't work when send as broadcasts without prior pre-selection.
It is important to understand that W command should be used within the NetLoader even if it has already been used in the application firmware before the NetLoader was started. This is because the application firmware and the NetLoader are separate firmware components and the pre-selection made in the application firmware will not be "passed" to the NetLoader.