DS125DF1610 CDR function bypass?

Stephen Sturges

Other Parts Discussed in Thread: DS250DF810, DS125DF1610

Is is possible to bypass the CDR function of this device and look at the raw unretimed outputs from the crosspoint switch. I know it has the eye tool but we wish to be able to look at the raw signal also in our test and measurement application. Reviewed the data sheet and block diagrams but did not see anything like this obvious.

Thanks,

Steve

over 9 years ago

0 Rodrigo Natal over 9 years ago

TI__Mastermind 19235 points

Yes. The DS250DF810 CDR bypass configuration depends on the CDR lock state.

If the CDR is locked, CDR bypass can be enabled by setting 0xA5[7:5]='000'
If CDR is not locked, CDR bypass can be enabled by setting 0x1E[7:5]='000'

Regards,

Rodrigo Natal

0 Stephen Sturges over 9 years ago in reply to Rodrigo Natal

Intellectual 290 points

This question for the DS125DF1610, not the DS250DF810

0 Rodrigo Natal over 9 years ago in reply to Stephen Sturges

TI__Mastermind 19235 points

To set the DS125DF1610 retimer to CDR bypass mode the following two steps are needed:

Channel register 0x09[5] must be set to 1.
Channel register 0x1E[7:5] must be set to '000'

Cordially,

Rodrigo Natal

DPS Applications Engineer

0 Stephen Sturges over 9 years ago in reply to Rodrigo Natal

Intellectual 290 points

Thanks for the info!

Can the CTLE adaptation be overridden? The desire with this to to override all CTLE, VGA and DFE functions so that the eye monitor can be used asset the quality of the of the incoming physical link and goodness of the board design less any impairment of the simple internal path of the device. Lot better solution than trying to midbus probe the physical link for debug.

Thanks again!

Steve

0 Rodrigo Natal over 9 years ago in reply to Stephen Sturges

TI__Mastermind 19235 points

One alternative is to set the retimer channel in question to adapt mode 0 i.e. "no adaption" mode. For this mode you force a specific EQ value; in your case you can force EQ value of 0 (i.e. no boost.) You may use the commands below to perform this configuration:

REG	Value	Comment
0x31	0x00	Set Adapt mode 0
0x2D	0x88	Enable EQ override
0x03	0x00	Set EQ = 00
0x3A	0x00	Set EQ = 00
0x0A	0x1C	Puts the CDR into RESET
0x0A	0x10	Releases the CDR from reset

0 Stephen Sturges over 9 years ago in reply to Rodrigo Natal

Intellectual 290 points

Thanks, Reading the datasheet is seemed like that was the case but good to confirm.

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DS125DF1610 CDR function bypass?