The max CHDR_W allowed is 512 (per the specification). But only the X410
device supports this. For all other USRPs, you should use 64 bits. This is
because 64-bit is enough for all the supported rates on other USRPs. This
parameter is set by the rfnoc_image_core, since blocks need to agree on the
CHDR width.
The MTU parameter ("maximum transmission unit", or maximum packet length)
is an FPGA-wide setting. It gets set by higher level logic so that all
blocks agree on the MTU setting. Software also discovers this setting and
will coerce Ethernet packet sizes to meet this requirement.
The MTU parameter will be set to 10 when CHDR_W=64. That means the MTU is
2^10 = 1024 CHDR_W-bit words. 1024 64-bit words is 8 KiB. It is possible to
use a different MTU, but I don't recommend it unless you have a good
reason. Setting it to 11 (16 KiB) means you are wasting RAM because most
Ethernet adapters only support up to 9 KiB packets anyway. Going to 9 (4096
KiB) means you have to send twice as many packets for the same amount of
data, which makes it much more likely that you will drop packets.
Wade
On Mon, Mar 14, 2022 at 4:18 AM sp h <stackprogra...@gmail.com> wrote:
> What's the max legal value for these parameters in RFNOC blocks?
> Can I for an RFNOC block set CHDR_W to 1024?
> We know for communication between RFNOC blocks in USRP is used AXI4 stream
> bus.....
> thanks in advance
>
> parameter CHDR_W = 64,
> parameter [5:0] MTU = 10
> _______________________________________________
> USRP-users mailing list -- usrp-users@lists.ettus.com
> To unsubscribe send an email to usrp-users-le...@lists.ettus.com
>
_______________________________________________
USRP-users mailing list -- usrp-users@lists.ettus.com
To unsubscribe send an email to usrp-users-le...@lists.ettus.com
