W5100 datasheet(37/72 Pages) WIZNET

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Sn_RX_RSR (RX Received Size Register) [R] [0x0426-0x0427, 0x0526-0x0527, 0x0626-

0x0627, 0x0726-0x0727] [0x0000]

This register notifies the data size received in RX Memory. As this value is internally

calculated with the values of Sn_RX_RD and Sn_RX_WR, it is automatically changed by RECV

command of Socket n Command Register(Sn_CR) and receiving data for remote peer. When

reading this register, user should read upper byte(0x0426,0x0526,0x0626,0x0726) first and

lower byte(0x0427,0x0527,0x0627,0x0727) later to get the correct value.

Ex) In case of 2048(0x0800) in S0_RX_RSR,

0x0426

0x0427

0x08

0x00

The total size of this value can be decided according to the value of RX Memory Size Register.

Sn_RX_RD (Socket n RX Read Pointer Register) [R/W] [0x0428-0x0429, 0x0528-0x0529,

0x0628-0x0629, 0x0728-0x0729] [0x0000]

This register offers the location information to read the receiving data. When reading this

(0x0429, 0x0529, 0x0629, 0x0729) later to get the correct value. It has a random value as its

initial value.

Caution: This register value is changed after the successfully executed receive command to

Sn_CR.

Ex) In case of 2048(0x0800) in S0_RX_RD,

0x0428

0x0429

0x08

0x00

But this value itself is not the physical address to read. So, the physical address should be

calculated as follow.

1. Socket n RX Base Address (hereafter we'll call gSn_RX_BASE) and Socket n RX Mask

Address (hereafter we'll call gSn_RX_MASK) are calculated on RMSR value. Refer to

the pseudo code of the 5.1 Initialization if the detail is needed.

2. The bitwise-AND operation of two values, Sn_RX_RD and gSn_RX_MASK give result the

offset address(hereafter we'll call get_offset), in RX memory range of the socket.

3. Two values get_offset and gSn_RX_BASE are added together to give result the

physical address(hereafter, we'll call get_start_address).

Now, read the receiving data from get_start_address as large as you want. (* There's a case

that it exceeds the RX memory upper-bound of the socket while reading. In this case, read

the receiving data to the upper-bound, and change the physical address to the gSn_RX_BASE.

W5100 Datasheet(PDF) 37 Page - WIZnet Co., Ltd