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W5100 Operation Modes

Oliver Schmidt edited this page Aug 22, 2018 · 2 revisions

The W5100 offers up to 4 'sockets' allowing to specify the operation mode for each socket individually.

MAC-Raw

In MAC-Raw mode the W5100 behaves pretty much like a CS8900A or a LAN91C96. The W5100 is usually only configured with a MAC address which is used by the W5100 to limit incoming frames to those sent to its MAC address (or broadcasts). MAC-Raw mode is only available for the first socket.

IP-Raw

IP-Raw mode is usable to implement non-UDP/non-TCP IP protocols like ICMP. The W5100 is usually configured with a full IP profile (IP addr, netmask, gateway). It transparently takes care of incoming/outgoing ARP and optionally of incoming ICMP Echo (aka Ping).

UDP

UDP mode is pretty simlar to IP-Raw mode but additionally takes care of header checksum calculation.

TCP

TCP mode is rather different from the other modes. Incoming/outgoing data isn't delimited by headers like in all other modes. Rather the W5100 behaves like a BSD socket delivering/taking a data stream - in chunks not necessarily related to data packets received/sent. The W5100 transparently takes care of TCP flow control by sending ACK packets. It advertises a receive window identical to the free space in the its receive memory buffer.

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