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This section describes the clock requirements for the DMC-620.
The DMC-620 provides a Low-power control interface using the Q-Channel protocol. The Low-power control interface is used to place the DMC into its low-power state, where the clock can be removed. The system can use the APB interface to put the DMC into its low-power state, and take it out of its low-power state.
The DMC has a Q-Channel interface that allows an external power controller to place the DMC into a low-power state.
It is a standard Q-Channel interface as defined in the AMBA® Low Power Interface Specification, Arm® Q-Channel and P-Channel Interfaces using the following signals:
When the DMC receives a request, it puts the DRAM into self_refresh before asserting qacceptn to accept the request that indicates the clk can be stopped.
The DMC denies requests to power down using the Q-Channel when geardown_mode is enabled. In this case, low-power mode can still be entered using the APB interface.
There is a separate Q-Channel interface for the pclk using the following signals:
The DMC never denies a request to power down the APB clock although it might be delayed based on APB activity.
See the AMBA® Low Power Interface Specification, Arm® Q-Channel and P-Channel Interfaces.