dma transfers between peripherals

Hello everybody!

In a NiosII system with a DMA and two custom peripherals, I need to transfer data between these two peripherals with DMA. My problem is that I don't know how to configure DMA to read and write to a fixed address (i.e. without address incrementing in both read and write ports). I'm able to configure it to perform memory to peripheral, peripheral to memory and memo to memo transfers using the HAL, but I can't imagine how to do it for peripheral to peripheral transfers. Any idea?

Looking to DMA documentation I've found that it must be much easier to do this kind of transfers accessing directly to registers, but I've read that I can't access registers directly if I'm using HAL system drivers. Does it mean that if I access directly to registers I can't use HAL drivers for DMA only, or for any component of my system?

Thank you for your time!