ARM Technical Support Knowledge Articles

How can I reconfigure PL340 after reset?

Applies to: PL340 AXI SDRAM Controller

Answer

The following are the steps that should be taken to reconfigure PL340 or the memory device:
 
1. All the AXI transfer requests for the current configuration must complete.
 
2. When there are no more AXI requests, you should program the memc_cmd register with Pause command.
 
3. Then continue polling the memc_status register to find out when PL340 has gone into Pause status.
 
4. When the memc_status has signalled it has gone into Pause status, you have to send the Configure command to memc_cmd register.
 
5. Then poll the memc_status register to ensure value 0x0 is returned. Once this is done, you can program your new configuration.
 
Another method of reconfiguring PL340 after reset is to use the Active Pause state. This can be used from release PL340 r1p0-00rel0. For this to work it is not necessary to wait for all AXI transactions to be completed before writing to the memc_cmd register with the ActivePause command. There is no need to go to the configure state, as register settings can be changed when in the low-power state.

Note that if you go into CONFIG state auto-refreshes will be stopped and data may be lost in the SDRAM.

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

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