DS250DF230: About HEO and VEO Values

Yuta Nishie

Part Number: DS250DF230

Hi,

DS250DF230 check the HEO and VEO when it tries to lock to the input.

If the HEO or VEO decreases bellow than the LOKC threshold, does it de-assert lock or keep lock despite of poor HEO or VEO?

Best Regards,

Nishie

9 months ago

+1 Drew Miller1 9 months ago

TI__Mastermind 24262 points

Hi Nishie-san,

Lock is de-asserted if HEO/VEO decrease below the threshold.

There are a couple registers impacting this. Please see data sheet for more details.

Register	Field Name	Description
0x67[5]	HV_LOCKMON_EN	Controls periodic monitoring of HEO/VEO for LOCK qualification.
0x76[7:4]	POST_LOCK_VEO_THR[3:0]	VEO threshold after LOCK is established.
0x76[3:0]	POST_LOCK_HEO_THR[3:0]	HEO threshold after LOCK is established.

Thanks,

Drew

0 Yuta Nishie 9 months ago in reply to Drew Miller1

Genius 3730 points

Hi Drew-san,

Thank you for your support.

Are you sure lock is de-asserted if HEO/VEO decrease below the threshold? Could you check it again?

The reason is that the lock does not come off even though the customer's device has a lower limit of HEO.

Programmable Guide also has the following options:

------------------------------------

7.15 HEO/VEO Lock Monitoring

Enable or disable Horizontal Eye Opening (HEO) and Vertical Eye Opening (VEO) monitoring for CDR lock

qualification. HEO/VEO lock monitoring will cause the CDR to fall out of lock if the HEO or VEO fall below the

configured threshold.

------------------------------------

Therefore, please check if Lock is not released.

Best Regards,

Nishie

0 Drew Miller1 9 months ago in reply to Yuta Nishie

TI__Mastermind 24262 points

Hi Nishie-san,

How has the customer configured register 0x76? What HEO is the customer observing where they expect lock to drop?

Thanks,

Drew

0 Yuta Nishie 9 months ago in reply to Drew Miller1

Genius 3730 points

Hi Drew-san,

Drew Miller1 said:
How has the customer configured register 0x76?

Drew Miller1 said:
What HEO is the customer observing where they expect lock to drop?

I will check.

The 5th bit of register 0x67 says "1: Enable periodic monitoring of HEO/VEO for lock qualification". What is the period of "periodic monitoring"? Please let me know if you have any information such as monitoring every X ms.

Best Regards,

Nishie

0 Drew Miller1 9 months ago in reply to Yuta Nishie

TI__Mastermind 24262 points

Hi Nishie-san,

I'll look into this and get back to you early next week.

Thanks,

Drew

0 Drew Miller1 9 months ago in reply to Drew Miller1

TI__Mastermind 24262 points

Hi Nishie-san,

I've discussed with my colleagues, but we don't have documentation readily available on exactly what the period of the periodic monitoring is. I can say that EOM is not constantly running due to power consumption.

Does the customer suspect an issue with their application due to HEO/VEO lock check period?

Thanks,

Drew

0 Yuta Nishie 9 months ago in reply to Drew Miller1

Genius 3730 points

Hi Drew-san,

Thank you for confirming. Let the customer know that we do not have accurate information about the monitoring period.

As shown in the following thread, a LOCK with an unintended data rate has occurred. To avoid this, we are considering countermeasures by changing the threshold of HEO/VEO.

https://e2e.ti.com/support/interface-group/interface/f/interface-forum/1306638/ds250df230-method-for-discriminating-two-input-data/4974644

https://e2e.ti.com/support/interface-group/interface/f/interface-forum/1300746/ds250df230-behavior-when-signals-of-different-data-rates-are-input/4974639

Best Regards,

Nishie

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DS250DF230: About HEO and VEO Values