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younggeun
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Registered: ‎12-21-2020

jesd204b subclass1 deterministic latency question

I am using vu7p.

and also i'm implementing jesd204b interface between adc(tx) and fpga(rx) as subclass1(config : continuous mode)

In my jesd configuration factors, F is 1 and K is 32. and using 4 lanes(lane 0 ~ lane 3)

So, multi-frame size, the MF is 32 and TW maximum value is 24(32-8) and minimum value is 8. the range is 8 ~ 24. 

my configuration for subclass1 is that sysref low to high transition is captured in adc and fpga at system clock's falling edge. 

after jesd link-up(rx sync high), when i read the jesd ip register about buffer adjust for each lane(0x830,0x870,0x8B0,0x8F0 for lane0 ~ lane3), if each read value(buffer adjust) or the smallest value is in the range  of TW range(8~24), does it mean that i get deterministic and repeatable latency from adc to fpga by jesd204b subclass1 perfectly?

To get this value in proper range, I can change the LMFC phase offset in ADC(tx).

For safety with deterministic and repeatable latency, do i have to read the buffer adjust register always(monitoring the buffer adjust)? if the value is not proper(value is changing or out of range, do i have to reset? 

 

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