Datasheet
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54 / 66 W5500 Datasheet Version1.0.9
SEND/SEND_MAC command after saving the data in Socket n TX buffer. But, if data is
bigger than its checked size, transmit the data after dividing into the checked size
and saving in the Socket n TX buffer.
If Sn_MR(P[3:0]) is not TCP mode(‘0001’), it is automatically calculated as the
difference between ‘Socket n TX Write Pointer (Sn_TX_WR)’ and ‘Socket n TX Read
Pointer (Sn_TX_RD)’.
If Sn_MR(P[3:0]) is TCP mode(‘0001’), it is automatically calculated as the
difference between Sn_TX_WR and the internal ACK pointer which indicates the point
of data is received already by the connected peer.
Ex) In case of 2048(0x0800) in S0_TX_FSR,
0x0020
0x0021
0x08
0x00
Note) Because this register for representing the size information is 16 bits, it is
impossible to read all bytes at the same time. Before 16 bit-read operation is not
completed, the value may be changed.
Therefore, it is recommended that you read all 16-bits twice or more until getting
the same value.
Sn_TX_RD (Socket n TX Read Pointer Register) [R] [0x0022-0x0023] [0x0000]
Sn_TX_RD is initialized by OPEN command. However, if Sn_MR(P[3:0]) is TCP
mode(‘0001’), it is re-initialized while connecting with TCP.
After its initialization, it is auto-increased by SEND command. SEND command
transmits the saved data from the current Sn_TX_RD to the Sn_TX_WR in the Socket n
TX Buffer. After transmitting the saved data, the SEND command increases the
Sn_TX_RD as same as the Sn_TX_WR.
If its 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.
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.