AM3351: I want to use WARMRSTn pin to reset peripherals on board

Hello,

What version of software are you running on the AM335x?

Regards,

Nick

linux ok335x 3.2.0 

Linux 3.2.0 is too old for us to support on the forums. I will be limited in the assistance I can offer.

Did you make sure to set the pinmuxing for the warmrstn signal?

Regards,

Nick

yes，i want to drive it low a few seconds

Did you check your device tree file to make sure the warmrstn signal is getting pinmuxed out of the chip?

Regards,

Nick

I used the devmem command to perform these register operations

Did you verify that the pinmuxing settings were actually taking effect? devmem2 is a userspace program, so I would expect that it does not have the proper permissions to modify control module registers.

Regards,

Nick

It should have changed the value of the register, because the system reset directly after I finished the above operation

It is very easy to see if the value of the register got updated. Just do devmem2 0xMemory_Address. I need you to verify that the register actually got updated (not just that you assume it was updated) before we do any more debugging.

Regards,

Nick

I am sure that the register has been updated and That I have read the value of the register using the method you provided

Hello,

I misunderstood your initial question. WARMRSTn does not require any pinmuxing. Taking a closer look at your register settings:
reset_iso: Ethernet Switch is isolated
PRM_RSTTIME: set RSTTIME1 and 2
PRM_RSTCTRL: perform warm global reset

Is this a good summary of your question?
"When I perform a warm reset by writing to PRM_RSTCTRL, I do not see any changes on the WARMRSTn pin. What is going on?"

Regards,

Nick

It is not possible to create a warm reset output with a duration of several seconds.

RSTTIME1 is a 8-bit field that can be used to select the number of CLK_M_OSC clock cycles for driving nRESET_OUT low. The period of each CLK_M_OSC clock cycle depends on your reference clock frequency. Let's assume you are using a 25MHz reference clock, the period of each CLK_M_OSC clock cycle would be 40ns. Therefore, the longest low pulse which you could generate is about 10us when RSTTIME1 is configured to its maximum value.

Regards,
Paul