LMH1228: there is difference between default value in programming guide and actual read result

K.Yaita

Part Number: LMH1228

Hi Team,

My customer found there is difference between default value in programming guide and actual read result.
----------------------------------------------
[Share Register]
0xE2: 0x00 (datasheet) -> 0x10 (actual)

[CTLE/CDR Register]
0x1E: 0x09 (datasheet) -> 0xE9 (actual)
0x2D: 0x80 (datasheet) -> 0x00 (actual)
----------------------------------------------
Could you confirm it?

Best Regards,
Yaita

over 5 years ago

0 Nasser Mohammadi over 5 years ago

TI__Guru* 93670 points

Hi Yaita-San,

Please refer to your earlier post for additional comment:

https://e2e.ti.com/support/interface/f/138/p/927677/3427528#3427528

As it relates to CTLE/CDR reg 0x1E, please refer to the LMH1228 programming guide. When reg 0x09[5] = 1'b1, then 0x1E[7:5] controls output mux setting. On the other hand if reg 0x09[5] = 1'b0 then 0x1E[7:5] reflects the status of the OUT0 mux setting. In default mode, 0x09[5] = 1'b0. It is possible that your customer 0x09[5] = 1'b0 and output is muted.

Regards,, Nasser

0 K.Yaita over 5 years ago in reply to Nasser Mohammadi

Guru 29720 points

Hi Nasser-san,

Thank you for your reply.
However regarding CTLE/CDR reg 0x1E, I would like to ask about default value which is after power-on.
Do you refer it isn't uniquely defined?

Best Regards,
Yaita

0 Nasser Mohammadi over 5 years ago in reply to K.Yaita

TI__Guru* 93670 points

Yaita-San,

In Default mode, reg 0x95[5] = 1'b0. This means device could be locked or not - based on pin and signal present. Therefor reg 0x1E[7:5] may have different values.

Regards,, Nasser

0 K.Yaita over 5 years ago in reply to Nasser Mohammadi

Guru 29720 points

Hi Nasser-san,

Thank you for your reply.
I assume there is no signal present in this case. If so, which pin shoud I check to confirm?

Best Regards,
Yaita

0 Nasser Mohammadi over 5 years ago in reply to K.Yaita

TI__Guru* 93670 points

Hi Yaita-San,

Please note LMH1228 data sheet pin description. There is not a pin that indicates whether signal is present or not. Through register programming, LOCK_N can be programmed to indicate signal presence.

Regards,, Nasser

0 K.Yaita over 5 years ago in reply to Nasser Mohammadi

Guru 29720 points

Hi Nasser-san,

I'm sorry I didn't explain it enough..
I understand reg 0x1E[7:5] may have different values however can't catch why 0x1E[7:5]=111(Mute) in default.

I checked my customer's schematic and OUT0_SEL=Floating (internal pull-up).
So I believe 0x1E[7:5] is read "111(Mute)" in this case.

Is my understanding correct?

Best Regards,
Yaita

0 Nasser Mohammadi over 5 years ago in reply to K.Yaita

TI__Guru* 93670 points

Hi Yaita-San,

Since OUT0_SEL is floating, due to the internal pullup, OUT0 is muted. Also, in default mode 0x09[5]=1'b0. These mean reg 0x1E[7:5] reflects or shows OUT0 setting or mute state(0x1E[7:5]=3'b111). So your understanding is correct.

Regards,, nasser

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LMH1228: there is difference between default value in programming guide and actual read result