This post tells about how SDRAM controller interacts with memory device. SDRAM controller interacts with memory device using specific commands. Here below some of them:
Bank Activate – command that makes SDRAM to open an internal bank in a row. This command should be applied before issuing read or write command. When this command is issued SDRAM opens new row address in requested internal bank.
Precharge – closes a specific internal bank in the active page/ all internal banks in the page.
Precharge all – closes all internal banks at the same time before executing an auto-refresh mode.
Read – command that makes SDRAM controller drive the column address. There is a delay between Bank Activate and Read commands, that is named as or CAS latency. Then data becomes available.
Write – here SDRAM controller also drives column address as well. There is also a delay between Bank Activate and Read commands, that is CAS latency. Then write data becomes valid.
Load mode – this command is used for SDRAM chip initialization.
Load Extended Mode – command having the same meaning as Load mode, but used for mobile SDRAM.
Auto-refresh and Self-refresh – commands used for controlling the way SDRAM contents is refreshed.