Select In Broadcast Mode (W) command
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Description (see command description format info here)
Select In Broadcast Mode command is used to pre-select a certain DS for subsequent programming via broadcast out-of-band (UDP) commands. Only a small portion of DS 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 configured reachable which is not always possible or convenient.
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 programming of 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 any other form of programming that involves addressing the DS by its IP-address.
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.