Can't reset PIO edge capture using IOWR_ALTERA_AVALON_PIO_EDGE_CAP

Altera_Forum · ‎03-01-2011

Dear experts,

I am Nios beginner. I wonder why I cannot reset the edge capture register using IOWR_ALTERA_AVALON_PIO_EDGE_CAP (to reset it inside my ISR)?

//after first interrupt, edge capture register became 1 and remain 1 no matter how many time I reset it using IOWR_ALTERA_AVALON_PIO_EDGE_CAP

pio_cnt=IORD_ALTERA_AVALON_PIO_EDGE_CAP(PIO_BASE);

alt_printf("pio_cnt= %x \n", pio_cnt); // pio_cnt=1

IOWR_ALTERA_AVALON_PIO_EDGE_CAP (PIO_BASE,0); //try to reset to zero

pio_cnt=IORD_ALTERA_AVALON_PIO_EDGE_CAP(PIO_BASE);

alt_printf("pio_cnt= %x \n", pio_cnt); // still pio_cnt=1 !!!!

I configured my PIO as (Input, Synchronous Falling Edge capture, Enable bit-clearing for edge capture register, Generate IRQ with edge trigger) using SOPC builder 10.1.

Your advice is highly appreciated. Thank you in advance.

Skw

Altera_Forum · ‎03-01-2011

Hi skw

In order to reset the edge capture register you must write one to the bits you want to reset, not write zero into the register.

Then, this line

IOWR_ALTERA_AVALON_PIO_EDGE_CAP (PIO_BASE,0);

must be changed in

IOWR_ALTERA_AVALON_PIO_EDGE_CAP (PIO_BASE, IRQ_BIT_MASK);

For example, if your irq signal is connected to pio bit 5, you'll define IRQ_BIT_MASK = 0x40

Regards

Altera_Forum · ‎03-02-2011

Hi Cris72,

Thanks a lot. My board worked after the change.

Best regards,

Skw

Altera_Forum · ‎06-25-2015

That's incredible! The same code with the same error is generated by Nios II SBT for Eclipse in the count_binary sample, that writes:

IOWR_ALTERA_AVALON_PIO_EDGE_CAP (BUTTON_PIO_BASE,0);

writting '0' instead '1'... I was one day looking for the error and debugging the program before coming to these fora, when I finally found the solution.

Why the sample code is wrong?

Additionally, I have problems writting the display with the code generated by the system... I will look again in the forum to see if this is due again to errors in it...

Regards,

Antonio

Altera_Forum · ‎11-01-2015

If the option Enable bit-clearing for edge capture register is turned off, writing any value to

the edgecapture register clears all bits in the register. Otherwise, writing a 1 to a particular bit

in the register clears only that bit.

https://www.alteraforum.com/forum/attachment.php?attachmentid=11355