Samsung S5PC110, Manual

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S5PC110_UM 1 DRAM CONTROLLER
1-9
1.2.3.2 Dynamic Power Down
The SDRAM device has an active/ precharge power down mode. This mode is entered if CKE becomes LOW. To
enter active power down mode minimum one row of a bank must be open. To enter precharge power down mode
CKE must be low.
If no AXI transaction enters the controller and the command queue becomes empty for a specific number of cycles
(
PwrdnConfig.dpwrdn_cyc
bit-field), the controller changes the memory device’s state to active/ precharge
power down automatically. Then, there are two ways to enter the active/ precharge power down state and it is
selected by
MEMCONTROL.dpwrdn_type
bit.
1. Active/ precharge power down mode: Enter power down without considering whether there is a row open or
not,
2. Force precharge power down mode: Enter power down after closing all banks.
If a new AXI transaction enters the controller, the controller automatically wakes up the memory device from
power down state and executes in a normal operation state.
1.2.3.3 Dynamic Self Refresh
Similar to the dynamic power down feature (Refer to Section 2.3.2 Dynamic Power Down), if the command queue
is empty for a specific amount of cycles (
PwrdnConfig.dsref_cyc
bit-field), the memory device enters self-refresh
mode. Since exiting power down mode requires many cycles, we recommend to choose a greater cycle size for
dynamic self-refresh entry than dynamic power down.
1.2.3.4 Clock Stop
To reduce the I/O power of the memory device and the controller, it is possible to stop the clock if the LPDDR /
LPDDR2 is in idle mode, or self refresh mode and DDR2 is in self refresh mode. If this feature is enabled, the
controller automatically executes the clock stop feature.
1.2.3.5 Direct Command
Use the direct command feature to send a command to the memory device through the APB3 port. This way, you
force the memory device to enter active/ precharge power down, self-refresh or deep power down mode.
1.2.4 PRECHARGE POLICY
There are two ways for the controller to decide precharge policy, namely:
•
Bank selective precharge policy
•
Timeout precharge