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Contributor
Contributor
7,930 Views
Registered: ‎10-23-2012

How to determine "ext_reset_in" in Processor System Reset (5.0) polarity?

I made a microblaze system for VC707 evb. In the design, there is a Processor System Reset. Then I find this reset is low active. Then I can check my previous design for KC705, it is high active. Then I compared the configuration of the IP and I found they are exactly same. I checked the PG164, found :

ext_reset_in : External Reset Input. Active-High or Low based upon the generic Ext Reset Active Polarity.

 

I am confused. What does mean " based upon the generic Ext Reset Active Polarity"? Is there an approach I can determine the polarity of "ext_reset_in" during my design stage? Otherwise, I found it is very annoying.

 

Thanks in advance.

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4 Replies
Professor
Professor
7,921 Views
Registered: ‎08-14-2007

Re: How to determine "ext_reset_in" in Processor System Reset (5.0) polarity?

In your MHS file should be a line that looks something like this:

 

 PORT sys_rst_pin = sys_rst_s, DIR = I, RST_POLARITY = 1, SIGIS = RST

 

That's where the polarity gets set.

-- Gabor
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5,575 Views
Registered: ‎10-29-2014

Re: How to determine "ext_reset_in" in Processor System Reset (5.0) polarity?

Hello Gabor,

 

I want to ask you it is necessary to have a ext_rst/cpu_rst, as I observed that in KC705, the cpu_reset comes through the dip switch that gives me the impression that the microblaze should work even without ext_reset_in to Processor System Reset?

 

Actually, I have a customized FPGA card with microblazed based design. At the Processor System Reset, I gave a active high reset from an external arm. But, when I download a bitstream to my hardware, and launch application.elf using sdk it never starts untill I put ext reset it from the arm.

 

In my arm code, reset is just a pulse that is supplies when the system starts otherwise it remains low?

 

Could you please explain me the role of cpu_reset/ext_reset_in for kc705 when the fpga is programed. 

 

Thanks in advance. 

 

Best regards, 

 

Vaibhav

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Professor
Professor
5,568 Views
Registered: ‎08-14-2007

Re: How to determine "ext_reset_in" in Processor System Reset (5.0) polarity?

You should probably start a new thread for this question.  In my experience you don't need an external reset signal for MicroBlaze.  Are you sure that the arm processor holds reset low all the time?  Perhaps it is high on startup until the first time you apply the pulse?  This could happen if you don't immediately program the GPIO of the arm to be actively driven until you enter the code that pulses it.  In any case, I don't have any experience with MicroBlaze on 7-series parts so you'd be best starting a new thread.

-- Gabor
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Moderator
Moderator
5,536 Views
Registered: ‎07-31-2012

Re: How to determine "ext_reset_in" in Processor System Reset (5.0) polarity?

Hi,

 

You can determine the polarity of ext_rst_in in Vivado IPI by selecting the particular pin and check for properties.

It is possible to alter the polarity as well.

 

Whereas in XPS, you can do the same via MHS file.

 

Regards

Praveen

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