First power on, and no clocks

Discussion around products based on ARM Cortex-A5 core.

Moderator: nferre

bestboy4
Posts: 7
Joined: Fri Jan 16, 2015 6:53 pm

First power on, and no clocks

Fri Jan 16, 2015 7:35 pm

I have designed a prototype board using the SAMA5D36.  All power rails are up and running.  VDDPLL is at 1.2V.  NRST, NTRST, and WKUP are pulled high. I have an external 32KHz crystal with no signs of life.  My 12MHz crystal shows some life, but is very low, like 300mV.  

Any clue why the crystals are not up?  Are there any other inputs I should be looking at?  Are there certain events that have to happen before is see the 32KHz clock?
bestboy4
Posts: 7
Joined: Fri Jan 16, 2015 6:53 pm

Re: First power on, and no clocks

Mon Jan 26, 2015 5:34 pm

I will answer my own post for others who might be looking for an explanation.  The documentation out there is very cryptic.  And for a newbie like myself it can be overwhelming. 

Apparently when dealing with a virgin board, the only clock that initiates is the 12Mhz clock for USB connection to SAM-BA.  Also, apparently a 300mV clock signal measured at the crystal with a 10x scope probe is normal. An external 32Khz clock is NOT present on a virgin board.  The internal 32Khz RC oscillator is going, but there is no way to determine that outside of the chip.  The external 32Khz crystal must be initiated by a program in flash, or debug (I'm still working on that part).

Also, for all you newbies out there like me.  JTAG must be "unlocked" by SAM-BA.  Through SAM-BA, go to NandFlash tab, ans select "Enable NandFlash" in the drop-down menu.  I also erased the Flash as well, but I'm not sure if that is needed.  Once that is done, JTAG should be able to see your stuff.  

I just have to say, it would have really sucked if I had decided to not put in a USB connection at specifically the HHSDPA/HHSDMA signals; I would have been so hosed!  And there is no documentation out there that says, "these signals must be connected if you want to have a chance of bringing up our custom board."  It used to be that a JTAG was all you needed.  Apparently now I have to unlock it through another connection.  

Return to “SAMA5D Cortex-A5 MPU”

Who is online

Users browsing this forum: No registered users and 3 guests