Understanding Inter-Processor Communication with Mailbox HW via mmap

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Understanding Inter-Processor Communication with Mailbox HW via mmap

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Hi,

I'm trying to understand how to use mailboxes to communicate between the hps side and the nios side and came across an altera tutorial. However, I don't understand some of the code. I've attached the address maps and code from their tutorial.

In my qsys file I have the mailboxes connected through the light weight bridge in hps and was wondering if 0xff260000 was the base address of the lightweight fpga slaves + the address base of Mailbox (from NIOS 0) peripheral as can be seen in the images attached.

mbox0_address = mmap(NULL, 0x10000, PROT_READ|PROT_WRITE, MAP_SHARED, fd, 0xff260000);

I also don't understand why mbox0_address is being added to 0x2000+2

while((*(volatile int*)(mbox0_address+0x2000+2) & 1) != 0 ) {}

If anyone can please explain.

Thank you

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