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Basic Questions About Ethernet

Question asked by n00b1024 on Jun 19, 2013
Latest reply on Mar 21, 2014 by Ragan_Dunham



I'm working on setting up the Ethernet module in a VF6, and have a few questions about how to do so. I'm pretty new to Ethernet, so some of these questions are fairly general.


1. How do I write data into the payload? In the manual, 42.4.6 (rev4) states that "writing to MMFR triggers a management frame transaction to the PHY device." Is that what I need to use? If MMFR is used for writing data into the payload, that register gives me 16 bits (only two octets) to work with. Should I instead write data directly to the Tx data buffer, whose location is specified in the transmit buffer descriptors (Table 42-191). If so, what would I use MMFR for?


2. What's EBD? There's a reference to it in Table 42-191, where it says that (referring to the bit that is set to generate interrupt flags)

"This field is valid regardless of the L [last frame] field and must be the same for all EBD for a given frame." I assumed that EBD meant Ethernet Buffer Descriptors, but this seems to imply that there are multiple buffers (and hence multiple INT bits) for a given frame. Does a payload contain more than one set of transmit buffer descriptors?



3. What does the Wrap transmit buffer descriptor do? The datasheet says that "0: The next buffer descriptor is found in the consecutive location, 1: The next buffer descriptor is found at the location defined in ETDSR [ENET_TDSR]," but I don't entirely understand what that means.


Thanks for reading!