W3100A Datasheet, PDF (28/63 Pages) List of Unclassifed Manufacturers – i2Chip W3100A

Active close
After completing data transmission and reception, the application uses the close command to terminate the
connection set-up. When the connection is terminated under the close command in such ESTABLISHED
state, it is called active close, and the process is illustrated in the left-hand side of the diagram above.
FIN_WAIT1 state: changes from the established state under the close command and transmits FIN packet.
Changes to FIN_WAIT2 when ACK for FIN is received fro the peer. Transmits ACK and changes to
CLOSING state when FIN is received from the peer. Transmits ACK and changes to TIME_WAIT when
FIN,ACK is received. In case of no reply, re-transmission is made, and if no reply is received until timeout
occurs, changes to CLOSED state.
FIN_WAIT2 state: stands by for FIN from the peer. In this state, W3100A does not receive data from the
peer, and if data is received, connection set-up is immediately terminated through RST. This is because
W3100A does not process additional data in half-close state.
CLOSING state: produced when the application closes simultaneously. Changes to TIME_WAIT when
ACK is received from the peer.
TIME_WAIT state: viewed as 2MSL (Maximum Segment Lifetime) WAIT State by TCP. In case FIN is
resent when the peer cannot receive ACK, there is a function where TCP resends the last ACK. In case TCP
connection is in 2MSL wait state, there is another function where other client, server is blocked from using
this connection. In W3100A, considering the limited resource and for efficient use of the channel, it
changes from this state to CLOSED state without waiting.
Passive close
In passive close, FIN is received from the peer to close in the ESTABLIHSED state as illustrated in the right-
hand side of the above diagram.
CLOSE_WAIT state: changed from ESTABLISHED state by receiving FIN from the peer. Transmits ACK
for FIN and creates closed interrupt at MCU. By processing the interrupt, MCU executes the close
command to W3100A and completes the connection close. But, if data to be sent still are left, that is
TW_PR value is not equal to TA_PR value, you should not issue the close command but wait until timeout
occurs or ignore close procedure and make progress next step like sock_init command.
LAST_ACK state: when close command is handed down by MCU, FIN is transmitted and stands by for
ACK. If no ACK is received, FIN Packet is re-transmitted. If no reply is received until timeout occurs, it
changes to CLOSED state.
TCP Data Transmission and Reception
Unlike UDP, TCP data transmission and reception is possible only after the connection set-up is made.
W3100A has exclusive memory for data transmission and reception, 8KB for transmission and 8KB for
reception. This memory can be set up as 1KB, 2KB, 4KB and 8KB by using RMSR (Rx data Memory Size
Register) and TMSR (Tx data Memory Size Register).
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