W5300 datasheet(85/128 Pages) WIZNET

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Sn_TX_FSR (SOCKETn TX Free Size Register) [R]

[0x08224+0x40n/0x224+0x40n] [0x00002000]

It notifies the free size of internal TX memory (the byte size of transmittable data) of SOCKETn.

The host

can’t write data through Sn_TX_FIFOR as the size bigger than Sn_TX_FSR.

Therefore, be sure to check Sn_TX_FSR before transmitting data, and if data size is smaller

than or same as Sn_TX_FSR, transmit the data with SEND or SEND_MAC command after

copying the data.

At the TCP mode, if the peer checks the transmitted DATA packet (if DATA/ACK packet is

received from the peer), Sn_TX_FSR is automatically increased by the size of transmitted DATA

packet. At the other modes, when Sn_IR(SENDOK) is '1', Sn_TX_FSR is automatically

increased by the size of transmitted data.

Ex1) Sn_TX_FSR = 64KB = 65536 = 0x00010000

Sn_TX_FSR(0x08224+0x40n/0x224+0x040n)

Sn_TX_FSR0(0x08224+0x40n/0x214+0x040n)

Sn_TX_FSR1(0x08225+0x40n/0x225+0x040n)

Reserved

‘1’

Sn_TX_FSR2(0x08226+0x40n/0x226+0x040n)

Sn_TX_FSR3(0x08227+0x40n/0x227+0x040n)

0x00

Ex2) Sn_TX_FSR = 33332 = 0x00008234

Sn_TX_FSR(0x08224+0x40n/0x224+0x040n)

Sn_TX_FSR0(0x08224+0x40n/0x224+0x040n)

Sn_TX_FSR1(0x08225+0x40n/0x225+0x040n)

Reserved

‘0’

Sn_TX_FSR2(0x08226+0x40n/0x226+0x040n)

Sn_TX_FSR3(0x08227+0x40n/0x227+0x040n)

0x82

0x34

Sn_RX_RSR (SOCKETn RX Received Size Register) [R]

[0x08228+0x40n/0x228+0x40n] [0x00000000]

It informs the byte size of received data in internal RX memory of SOCKETn.

The host

can’t read data through Sn_RX_FIFOR as the size bigger than Sn_RX_RSR. So, after

checking Sn_RX_RSR, the host read the received data though Sn_RX_FIFOR smaller than or

as same size as Sn_RX_RSR, and copies the data into the host system memory. After memory

copy, the host should inform the copy completion of data to W5300 by RECV command.

W5300 Datasheet(PDF) 85 Page - WIZnet Co., Ltd