SN75LVPE5412: Programming sequence in I2C mode

Roy Hsu

Part Number: SN75LVPE5412
Other Parts Discussed in Thread: DS320PR810

Hi Team,

I have a few questions about the programming sequence in I2C mode.

1. When should the external I2C master start programming the SN75LVPE5412/5421? Should we start programming the device before PD goes low and right after Vcc becomes stable? Because I assume that once PD goes low, the device will be active and PCIe link training will start.

2. What would happen if we update the EQ/VOD settings after the PCIe link training? Would it affect the stability of the link?

Thanks!

Roy

over 2 years ago

0 Nasser Mohammadi over 2 years ago

TI__Guru* 93570 points

Hi Roy,

1). Best option is to program before PD goes un-asserted(inactive or low). Of course customer can use EEPROM or pin settings so new settings will take place at power up.

2). Yes it is possible. Based on what we've seen it can link up at lower data rate. Whether the link becomes stable or nor it depends on the CTLE setting versus the actual environment/application.

Regards,Nasser

0 Roy Hsu over 2 years ago in reply to Nasser Mohammadi

TI__Genius 9360 points

Hi Nasser,

1. The customer would have preferred to use EEPROM if the SN75LVPE5412 supported it. For some reason this device does not support EEPROM mode, only the DS320PR810 supports this mode.

2. OK. Then I believe the best way would be to complete the EQ/VOD setting before link training starts.

Thanks!

Roy

0 Nasser Mohammadi over 2 years ago in reply to Roy Hsu

TI__Guru* 93570 points

Hi Roy,

Yes you are correct EEPROM mode is disabled on this part.

Agreed we should program the device while PD is active or before we release PD pin. Some customers use BMC controller to program the device. I suppose this is done during PERST# active.

Regards,Nasser

0 Roy Hsu over 2 years ago in reply to Nasser Mohammadi

TI__Genius 9360 points

Hi Nasser,

Is it also OK to program this device when Vcc is stable but PD is high (inactive)?

Thanks!

Roy

0 Nasser Mohammadi over 2 years ago in reply to Roy Hsu

TI__Guru* 93570 points

Hi Roy,

PD is true on high so it is active when it is high. Yes it is ok to program the device when PD is high.

Regards,Nasser

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SN75LVPE5412: Programming sequence in I2C mode