On Wed, Sep 28, 2016 at 10:14:52AM -0700, Eric Nelson wrote:
> Thanks David,
>
> On 09/28/2016 09:42 AM, David Laight wrote:
> > From reading this it seems that the effect of FEC_RACC_SHIFT16 is to
> > add two bytes of 'junk' to the start of every receive frame.
>
> That's right. Two bytes of junk between the MAC header and the
> IP header.
That's wrong. FEC_RACC_SHIFT16 adds two bytes to the _beginning_ of
the packet, not in the middle of the packet:
7 RX FIFO Shift-16
SHIFT16
When this field is set, the actual frame data starts at bit 16
of the first word read from the RX FIFO aligning the Ethernet
payload on a 32-bit boundary.
NOTE: This function only affects the FIFO storage and has no
influence on the statistics, which use the actual length
of the frame received.
0 Disabled.
1 Instructs the MAC to write two additional bytes in front
of each frame received into the RX FIFO.
*in front* of the frame - that's before the Ethernet header. Not between
the ethernet and IP headers.
--
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