Different pull up and pull down in sysboot of AM335x IDK?

Sysboot options are documented in TRM chapter 26.

regards.

Thanks for your response. In that section i don't find anything related to pull up or pull down resistor values.

regards,

Ibram

Thank you Biser.

Is there any specific reason for putting different pull up and pull down in AM335x IDK base board rev 1.2? this is where i got confused.

Regards,

Ibram

Ibram,

maybe we don't fully understand your question...

Ibram sahibu said:

Is there any specific reason for putting different pull up and pull down in AM335x IDK base board rev 1.2? this is where i got confused.

Different to what? The Sysboot options define several operating modes and boot sequence. They are set for the requirements of our industrial protocol developments (see IA-SDK). Depending on your project requirements you may want to do something different. PU/PD just define the logic level needed after power on reset.

Regards.

Frank,

now its cleared for me.

one more clarification. i want to have 2 ethernet port. one is from PRU and other one is from GEMAC.

can i have this combination in my board? 

Regards,

Ibram

Ibram,

I think generally yes. However Pin-mux discussions should always be done in the context of complete schematics (or at least full analysis of all interfaces required). You should first use the pin-mux tool a quick analysis.

You also need to clarify:

- should both Phy be driven from same MDIO or independent?

- what software/protocol requirements do you have? We only have support for some industrial ethernet protocols on PRU so far.

Regards.

Frank,

i am using independent MDIO.

our requirement is industrial ethernet protocols. do you have support for those in linux?

Ibarm,

please have a look at the IA-SDK offering. We currently support EtherCAT slave, Profibus slave and to some extent Powerlink (in combination with 3P). More slave protocols are in development. However our SDK is currently based on Sys/Bios as Linux doesn't fulfill our real-time requirements. Other industrial protocol options maybe available from 3Ps too - such as EtherCAT master on QNX using the Gbit switch.

regards.

I'm not sure your question about why different pull-up/pull-down resistor values were used on the SYSBOOT pins was completely answered.

As Biser mentioned, this depends on what is connected to these pins.

You need to consider the worst-case internal leakage current possible for each IO and size your external resistors such they will be able to pull the signal above or below the valid logic levels defined for the respective IO.  If other devices are attached, you may need to add their internal leakage to the AM335x internal leakage when calculating the maximum resistor value required to pull the signal to the worst-case valid logic level of all attached devices.

Regards,
Paul

thanks paul. it was cleared for me.i have decided to put 4.7K since max current leakage for other purpose is 6mA only.