2.5.3 SPI Collator power Q-Channel

The SPI Collator has a power Q-Channel interface that accepts requests from an external source, such as the system power controller.

When signal qactive_col is LOW, it indicates that all SPIs to the SPI Collator are in their normal state of either 0 (edge-triggered, or active-HIGH), or 1 (edge-triggered, or active-LOW), and therefore all messages are sent to the Distributor.

If qactive_col is HIGH, the SPI Collator rejects any attempt to enter a low-power mode.

If qreqn_col is LOW and is accepted, the SPI Collator enters low-power mode and the AXI4-Stream channels to the Distributor are flushed out to ensure that there are no messages in progress. When accepted, you can reset the SPI Collator safely without having to also reset the Distributor. You can also reset the Distributor, but you must first complete the instructions that are described in the subsections of section 3.6 Power management before the Distributor can be powered down.

Note:

  • When the SPI Collator and Distributor are both in the same domain, the power Q-Channel interface is redundant and can be tied off.
  • In low-power mode, it is only safe to stop the Collator clock if all edge-triggered interrupts into the SPI Collator are pulse extended to ensure that edges are not missed.
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