W3100A Datasheet, PDF (32/63 Pages) List of Unclassifed Manufacturers – i2Chip W3100A

TCP Retry Time Adjustment
W3100A uses IRTR (Initial Retry Time-value Register) and RCR (Retry Count Register) to adjust the timer
to be used in re-transmission of TCP.
TCP re-transmission is executed when the initial retry timer expires, and the retry timer is reset at the value
of * 2. Such a process is repeated according to the RCR value, and in the last retry, timeout interrupt occurs
and then gives up.
Formula of timeout value:
IRTR: Initial Retry Time-value Register
RCR: Retry Count Register
IRTR * 100us = start timeout second
Total timeout value until give-up = (IRTR * 100us) *(2^RCR-1)
Internally, the default value of IRTR is 0x07D0 and RCR is 0x06, where initial retry takes place at 200ms
and the retry frequency becomes 6. Therefore, unless these registers are revised, retry is made at 200ms,
600ms, 1400ms, 3000ms, 6200ms, 12600ms each and gives up at the final 12600ms.
3. UDP Protocol
UDP is a connectionless protocol. No connection set-up or termination process is needed, thereby creating
lesser load.
UDP Initialization Process
In order to use UDP of W3100A, the Cx_SOPR (Socket Option/Protocol register of Channel x) protocol field
of the corresponding channel needs to be set as SOCK_DGRAM(0x02) before socket initialization. Unlike
TCP, data transmission and reception is possible at UDP without any connection set-up process.
UDP Data Transmission and Reception
UDP transmission is activated similarly to TCP. All data received at its port can be received, and MCU
needs to analyze the header information of the data to verify transmitting IP and port to confirm the
corresponding data before processing.
Set-up of transmission and reception memory size is identical to TCP.
UDP Data Transmission
UDP transmission is activated similarly to TCP. Calculating the free buffer size of the memory, data
copying and Cx_TW_PR are identical. The difference is the usage of Cx_TR_PR instead of Cx_TA_PR.
Another difference is that destination IP and port need to be set. In other words, if the destination IP and
oˆ™‹ž™Œ‹Gp•›Œ™•Œ›Gj–••ŒŠ›› G~¡ˆ™‹GO~p•Œ›SGp•ŠUPG
ZY