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Altera_Forum's avatar
Altera_Forum
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19 years ago

IOWR/IORD problem, what does IORD return?

Nios2 is new to me and I'm developing a custom component on it.

I have my Avalon regester interface ready.

I can IOWR a integer into the regester to perform the function, but fail to IORD from the same reg. (IORD the same reg give me 0). The reg is 32 bit wide, is there anything to do with the address?

It's not one of the delay problem, because i wrote a while{} loop to read it, but still, can't get what I just IOWR.

It could be silly, but please answer it in detail, since i'm really new here.

3 Replies

  • Altera_Forum's avatar
    Altera_Forum
    Icon for Honored Contributor rankHonored Contributor
    19 years ago

    That should have worked. You might want to copy and paste the code fragments. Are you sure you have the readdata signal in your component wired up correctly?

  • Altera_Forum's avatar
    Altera_Forum
    Icon for Honored Contributor rankHonored Contributor
    19 years ago

    Is this a custom SOPC Component using VHDL/verilog?.

    Did you provide the capability of reading this register?

    This could also be a HW timing issue with reads and/or writes. If this is a brand new Component I would recommend simulating the component or using Signal Tap to watch the appropriate registers, control signals, and data buses.
  • Altera_Forum's avatar
    Altera_Forum
    Icon for Honored Contributor rankHonored Contributor
    8 years ago

    I am also getting the same issue, using IOWR_32DIRECT doesn't produce error and printfs after that call work, but as soon as I call IORD_32DIRECT, the printfs afterwards do not show. Does anyone know any possible reasons as to why my code is hanging up at IORD_32DIRECT?

    (The usleep(20000)s are a way to "flush" the stdout buffers because I was having this issue: https://www.altera.com/support/support-resources/knowledge-base/solutions/rd07292005_415.html) 

    #include <alt_types.h>#include <io.h># include <string.h># include "system.h"
# include "sys/alt_dma.h"
# include "sys/alt_flash.h"# include "sys/alt_flash_dev.h"# include "sys/alt_flash_dev.h"# include "sys/alt_stdio.h"//for alt_putbufflush()# include <stdio.h>
int main()
{
//===============Set Address===============
         //int *THE_ADDRESS;
         //THE_ADDRESS = (int)ADDRESS_SPAN_EXTENDER_0_WINDOWED_SLAVE_BASE;
         int THE_ADDRESS;
         THE_ADDRESS = (int)SINKSOURCE_0_BASE;
//===============Write===============
         printf("Reading from Address: %08x \n", THE_ADDRESS);
                   usleep(200000);
         printf("THE_ADDRESS: %08x \n", THE_ADDRESS);
                   usleep(200000);
         int write_val = 0xffff;
         IOWR_32DIRECT(THE_ADDRESS,0, write_val);
                   usleep(200000);
         printf("Wrote %08x to %08x \n", write_val, THE_ADDRESS);
                   usleep(200000);
//===============Read===============
                   usleep(200000);
         int val =  IORD_32DIRECT(SINKSOURCE_0_BASE, 0); //PROGRAM STOPS HERE!!!!!!!!!!!!!!!!!!!!!!!!!!!!!
                   usleep(200000);
         printf("Value at %08x: %08x \n", SINKSOURCE_0_BASE, val);
                   usleep(200000);
 return 0;
}