DS280DF810EVM: Clock and prbs function question

Hi HsuChiang,

1. Connecting an external calibration clock source for the calibration clock is not necessary. Device U1 is an on-board 25MHz oscillator. By shunting J213 Pins 1-3, this provides 25MHz to the CAL_CLK_IN pin.

2. The PRBS signal comes from both TxnP and TxN, because the output is differential.

3. Yes, you can do this. You will need to set one of the signal outputs to transmit PRBS, then connect the output to another channel's Rx input. Assuming you are transmitting at a data rate the channel is programmed to lock to, the DS280DF810 Rx channel will lock to the PRBS input, and you will be able to see the EOM.

All of these functions can be performed using the SigCon Architect GUI to control the EVM.

Regards,

Michael

Hi Michael

Yes, i am using the SigCon Architect GUI to control the EVM.

But when i enable the PRBS Generator on the Channel 0, I don't see the data output from the Tx0P and Tx0N.

All the setting i useed is the default setting.

The Channel indicator shows the CDR is Unlocked is that causes the problem?

Could i use the internal clock source to lock the CDR ? or I need to use the external BERT to let the CDR to be locked?

Or anything i omit to configure to enable the PRBS generator, if i miss some procedure could you provide some configured procedure for me ?

Now i am following the DS280DF810EVM_SNLU214 user guide, do there has the more detail information about control the  DS280DF810EVM on the SigCon?

Thanks.

Hi HsuChiang,

Please see answers to your questions below:

1. If the CDR is unlocked, then the PRBS generator will not run correctly.

2. The internal clock source is for the VCO. An input is required on RxnP/N in order for the VCO (and in turn, the CDR) to lock. In order to output a signal at a specific data rate, you will need to provide a data rate for the DS280DF810 to lock to. Note that the 25 MHz calibration clock is used for ensuring PPM, and it is not a reference clock for the internal VCO of the DS280DF810.

3. I would recommend the following steps before running the PRBS generator:

a. Send a clock signal that is a divide-by-2, 4, 8, or 16 factor of the data rate you wish to send the PRBS signal. For example, if you wish to send PRBS at 28.78125 Gbps, you can send a differential sine wave at 28.78125 GHz/8 = 3.59765625 GHz into Tx0P/N. This is effectively the same as a 7.1953125 Gbps input signal.

b. The DS280DF810 can be configured to lock only at the divide-by-1 data rate so that the VCO is set to 28.78125 GHz. Once the CDR has declared lock, then you can start the PRBS generator.

All the information we have about controlling the DS280DF810EVM in SigCon Architect is available in the User's Guide. There is no alternate document.

Thanks,

Michael

Thanks you for your prompt reply.

In the 3-a, You say i can send a differential sine wave into Tx0P/N is that correct? or that is the  Rx0P/N?

I'll work on it.

Regrads,

John.

Hi John,
Yes it should be Rx.

Regards,
Lee

Hi Sir 

Need your assistance again.

I'm using the SigCon.

I use the sine wave generator with the balun to produce the differential wave in order to lock the CDR and it is successfully to  be locked.

But when i use the PRBS generator, there is something weird.

When i enable PRBS generator of the channel which CDR is locked,  

1. choose the CDR tab In the High level Page

2. In combobox of  the Post Lock Output

3. Choose the PRBS generator, but the TxN and TxP don't have any data come out.

4. Choose the retimeddata, there has data come out, the data which is captured by the oscilloscope and the screenshot  attached.

I suppose that the data should come out when i choose the PRBS generator but it didn't.

However  the data comes out when i choose the retimeddata.

I suspect that this data is possibly to be the wave of the  PRBS's pattern superposition on the wave of the  retimer's data ?

Q.

1. Is it the correct wave form and the correct operation?

2. Any suggestion?

Thank you again.

Regards

John.

The PRBS generator should be enabled on the PRBS tab and not on the CDR tab. Go to the PRBS tab, select the desired channel. On the left you will have the option of selecting PRBS pattern and enabling the generator with a single click.

Cordially,

Rodrigo Natal
HSSC Applications Engineer

Hi Rodrigo

Thanks for your reply.

Now i feed the 3Ghz differential sine wave to the Ds280.

1. Setting the Date Rate to the 24 Gbps

2. Setting the divide factor to the 4.

3. The CDR is locked.

 Re-timed data will be output at what data rate, 3Ghz or 24 Gbps?

Could you share the wave form of the PRBS pattern generated by the DS280DF?

I want to compare with mine.

Thanks.

Regards,

John

Hi. Assuming that the DUT channel has valid input data and CDR is its locked, then yes, enabling PRBS generator on the GUI PRBS tab is all that you should need to do to be able to generate PRBS data.

Hi:

Here are questions regarding CDR lock: (DS280 EVM)

1). while use sine wave gen (CW gen), apply to RX+/RX-, frequency in the range of 3Ghz - 5Ghz, CDR locks. 

2). while use pseudo random data, magnitude at 400mv P-P, frequency at 5Ghz, CDR unlocked!, Please kindly 

advise what could be the causes? 

Thank you, 

Roger

As per the product datasheet, the DS280DF810 CDR only supports full rate, half rate and quarter rate divider ratios when standard data is being transmitted. However, lower divider ratios can be handled when the input data is 1010 clock pattern (i.e. sine wave.)

Hello Rodrigo:
1). If the intent output 24Gbs, quarter divider is selected then a 3Ghz CW is feed into the DS280, then every thing seems works fine. This including PRBS gen.
2). When use 5.1?/(I couldn't remember exactly the speed, but it is a standard speed), PRBS signal and feed it into the DS280, it doesn't lock (the CDR), see the photo I just sent. Half rate was selected.
3). Please kindly advise what could be the causes?

To configure the retimer to enable CDR operation at 5.1 Gbps, below are my recommended settings:

STEP	SHARED/ CHANNEL REGISTER SET	OPERATION	REGISTER ADDRESS [HEX]	REGISTER VALUE [HEX]	WRITE MASK [HEX]	COMMENT
1	Channel	Write	60	00	FF	20.4 Gbps rate
2	Channel	Write	61	B3	FF	20.4 Gbps rate
3	Channel	Write	62	00	FF	20.4 Gbps rate
4	Channel	Write	63	B3	FF	20.4 Gbps rate
5	Channel	Write	64	FF	FF	Set PPM tolerance to max
6	Channel	Write	09	04	04	Enable override for divider
7	Channel	Write	18	xx	xx	xx
				xx	xx	xx
				20	70	Force divide-by-4, 5.1 Gbps ≤ data rate ≤ 7.1 Gbps
8	Channel	Write	0A	0C	0C	Assert CDR reset (6.3)
9	Channel	Write	0A	00	0C	Release CDR reset (6.4)