There are a few scenarios in which the system's resource usage indicator for the amount of delay used may falsely signal that no more delay is available—even though the total used is less than 100%. These situations are extremely unlikely, but just in case it arises for you, we are providing the details and the reasons for this false indication.
In the HAL, system delay is spread across all four of its DSP processors. The total amount of delay that is possible is 80 seconds, but the most that can be used at one time by an individual block is 20 seconds (because each individual DSP chip provides 20 seconds of delay—and blocks cannot span multiple DSP chips).
Now, let's assume you have the following situation: You drop an individual Delay block on the Processing Map and configure it to use a large amount of delay. Every time you add another channel/node to the block, the total delay for that block increases by the configured delay amount. For example, if a Delay block is configured at 5 seconds of delay and has one node, that Delay block uses 5 seconds. If two more nodes are added, the block then uses 15 seconds. If two more nodes are added (for a total of 5 nodes), the block then uses 25 seconds. At this point, the total delay used by the system could be well under its allowed maximum of 80 seconds, but the particular DSP processor to which this Delay block is assigned is over 20 seconds. Therefore, the configuration cannot be applied and the Delay Resource Usage bar turns red.
Once again, we want to emphasize that the occurrence of this situation in a typical configuration is EXTREMELY unlikely. Delays are usually configured in the range of several milliseconds, not multiple seconds.