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Question about delay step of MMDC Read and Write calibration

Question asked by ko-hey on Apr 25, 2019
Latest reply on Apr 26, 2019 by Yuri Muhin

Hi all,


I have question about delay step of MMDC Read and Write calibration.

Could someone answer for the delay step ?


The following description is in the MMDCx_MPRDDLCTL of reference manual.


(RD_DL_ABS_OFFSET0 / 256) * MMDC_CH0 AXI clock (fast clock).

So for the default value of 64 we get a quarter cycle delay.


I understand that the AXI Clock (fast clock) is recognized as 1/2 of SDRAM Clock.

(264 MHz when the SDRAM Clock is 528 MHz)



AXI Clock (fast clock) is 1/2 of SDRAM Clock.

Is the above understanding correct?



Is it actually 1/256 unit of SDRAM Clock?



It's easy to understand that a quarter cycle is the default that takes the middle of data that changes in half a cycle (DDR).


However, if it is 4/1 of the AXI clock, it will be 1/2 of the DDR clock, and the default value and the adjustment range are too large.

In addition, the calibration log by the test tool is actually 1 0 1 The changing 0 (OK) range is also equivalent to an average of 76 steps in the OFFSET value, which translates into an impossible result exceeding 1124 ps and a half cycle (947 ps) of the SDRAM clock.