ARM Technical Support Knowledge Articles

In PL340 what is the difference between stop_mem_clk and auto_power_down?

Applies to: PL340 AXI SDRAM Controller


stop_mem_clk feature is only used in devices that can support this. This just means that the clock will only toggle when the memory device requires it to carry out functions. Note this can't be used with DDR as the DLL in the memories would lose lock (can be used with MDDR and SDR because there isn't a DLL in them).

In auto_power_down, the memory interface automatically places the SDRAM into power-down state by deasserting CKE when the command FIFO has been empty for PowerDownPrd memory clock cycles.

For auto_power_down, there may be a delay from cke going high to when the next access can be carried out. Therefore there is a compromise between saving power and overall bandwidth achievable.

Article last edited on: 2008-09-09 15:47:52

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