W5500 Datasheet, PDF (56/65 Pages) List of Unclassifed Manufacturers – Supports 8 independent sockets simultaneously

value 0xFFFF, (greater than 0x10000 and the carry bit occurs), then the carry bit is
ignored and will automatically update with the lower 16bits value.
Sn_TX_WR (Socket n TX Write Pointer Register) [R/W] [0x0024-0x0025] [0x0000]
Sn_TX_WR is initialized by OPEN command. However, if Sn_MR(P[3:0]) is TCP
mode(„0001‟), it is re-initialized while connecting with TCP.
It should be read or to be updated like as follows.
1. Read the starting address for saving the transmitting data.
2. Save the transmitting data from the starting address of Socket n TX
buffer.
3. After saving the transmitting data, update Sn_TX_WR to the
increased value as many as transmitting data size. If the increment
value exceeds the maximum value 0xFFFF(greater than 0x10000 and the
carry bit occurs), then the carry bit is ignored and will automatically
update with the lower 16bits value.
4. Transmit the saved data in Socket n TX Buffer by using SEND/SEND
command
Sn_RX_RSR (Socket n Received Size Register) [R] [0x0026-0x0027] [0x0000]
Sn_RX_RSR indicates the data size received and saved in Socket n RX Buffer.
Sn_RX_RSR does not exceed the Sn_RXBUF_SIZE and is calculated as the difference
between „Socket n RX Write Pointer (Sn_RX_WR)‟ and „Socket n RX Read Pointer
(Sn_RX_RD)‟.
Ex) In case of 2048(0x0800) in S0_RX_RSR,
0x0026
0x08
0x0027
0x00
Sn_RX_RD (Socket n RX Read Data Pointer Register) [R/W] [0x0028-0x0029] [0x0000]
Sn_RX_RD is initialized by OPEN command. Make sure to be read or updated as
follows.
1. Read the starting save address of the received data
2. Read data from the starting address of Socket n RX Buffer.
3. After reading the received data, Update Sn_RX_RD to the increased value as
many as the reading size. If the increment value exceeds the maximum value
0xFFFF, that is, is greater than 0x10000 and the carry bit occurs, update with
the lower 16bits value ignored the carry bit.
4. Order RECV command is for notifying the updated Sn_RX_RD to W5500.
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W5500 Datasheet Version1.0 (August 2013)