SPRUHZ7K August 2015 – April 2024 AM5706 , AM5708 , AM5716 , AM5718 , AM5718-HIREL
Chip select 1 is not supported on this device.
The EMIF controller supports automatic output impedance (ZQ) calibration for DDR3/DDR3L memories. The ZQ calibration can be enabled per CS by setting the EMIF_SDRAM_OUTPUT_IMPEDANCE_CALIBRATION_CONFIG[31] ZQ_CS1EN and EMIF_SDRAM_OUTPUT_IMPEDANCE_CALIBRATION_CONFIG[30] ZQ_CS0EN bits. The EMIF supports three types of ZQ calibration commands:
The EMIF automatically issues ZQINIT command during DDR3/DDR3L memory initialization. It also issues ZQCS command each time the EMIF_SDRAM_OUTPUT_IMPEDANCE_CALIBRATION_CONFIG[15:0] ZQ_REFINTERVAL bit field expires. In other words, the ZQ_REFINTERVAL defines the interval between two ZQCS commands. When ZQCS command is issued, the EMIF waits and blocks any other command for EMIF_SDRAM_TIMING_3[20:15] ZQ_ZQCS + 1 number of DDR clock cycles.
If the EMIF_SDRAM_OUTPUT_IMPEDANCE_CALIBRATION_CONFIG[28] ZQ_SFEXITEN bit field is set to 0x1, the EMIF issues ZQCL command every time it exits self-refresh, active power-down and precharge power-down modes. When ZQCL command is issued, the EMIF waits and blocks any other command for (EMIF_SDRAM_OUTPUT_IMPEDANCE_CALIBRATION_CONFIG[17:16] ZQ_ZQCL_MULT + 1) × (EMIF_SDRAM_TIMING_3[20:15] ZQ_ZQCS + 1) number of DDR clock cycles.
If a separate calibration resistor is used per device, the ZQ calibration can be performed simultaneously over both CSs. To enable ZQ calibration to be performed simultaneously over both CSs, the EMIF_SDRAM_OUTPUT_IMPEDANCE_CALIBRATION_CONFIG[27] ZQ_DUALCALEN bit must be set to 0x1. If ZQ_DUALCALEN is set to 0x0, the EMIF performs ZQ calibration serially per chip select.
The ZQINIT is a non periodic command issued only once during DDR initialization as opposed to the ZQCL and ZQCS calibration commands which are issued by the EMIF periodically at regular intervals.