TI-JESD204-IP: SYNC and SYSREF become inactive in 1.2 ms but data continues to be received on JESD RX

Trushal Alshi

Part Number: TI-JESD204-IP
Other Parts Discussed in Thread: ADS52J90

Tool/software:

I have explored the TI-JESD IP in loop back mode where SYSREF from TX looped back to RX and continues to run.

In our prototype board, we are using LMK0426 and ADS52J90 for clock generation and data acquisition where we see that the JESD is locking and continues to receive the data.

But we see that the SYSREF discontinues in around 1.2 ms while the data is still being received with valid data on JESD.

LMK0426 has been set in "SYSREF Request mode" which basically looks for SYNC signal. (I am using SYNC inverted from SYNC~ from TI JESD IP).

We intend to use SYNC as two ADCs to be connected to same JESD IP. My question is whether this discontinuation of SYSREF is ok and expected behavior.

Every time JESD is reset and starts, we see above behavior.

Hope to hear soon.

Thanks & regards,

Trushal

8 months ago

0 Sachin H K 8 months ago

TI__Expert 7725 points

Hi,

Which JESD subclass are you using ?

0 Trushal Alshi 8 months ago in reply to Sachin H K

Prodigy 140 points

It is JESD204B, subclass 1 for ADC (default JESD version of ADS52J90 as ENABLE_JESD_VER_CONTROL is deasserted by default). In TI_JESD IP, no specific subclass is not mentioned. The transceiver IP instantiation also does not show up any specific JESD version and subclass. Is there any way to check version and subclass in TI_JESDC (TI204C-IP-Release-v1.12). It is 8b/10 encoder and 64 bit wide data width in TI_JESD IP.

+1 Ameet Bagwe 8 months ago in reply to Trushal Alshi

TI__Intellectual 2410 points

Hi Trushal,

The TI JESD IP supports subclass 1. The SYSREF is used by the IP only as a way of aligning the local multiframe to the SYSREF positive edge (which can then be used for deterministic latency). Once the link comes up, the SYSREF has no other function. The JESD IP will function even in total absence of SYSREF, if the SYSREF input to the IP is tied to '0'.

Regards,

Ameet

0 Trushal Alshi 8 months ago in reply to Ameet Bagwe

Prodigy 140 points

Hi Ameet,

Thanks you for the clarification. It helped a lot.

Regards,

Trushal

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TI-JESD204-IP: SYNC and SYSREF become inactive in 1.2 ms but data continues to be received on JESD RX