W5100 datasheet(63/72 Pages) WIZNET

63 / 72 page

6.3.1 Device Operations

The W5100 is controlled by a set of instruction that is sent from a host controller, commonly

referred to as the SPI Master. The SPI Master communicates with W5100 via the SPI bus which

is composed of four signal lines: Slave Select(/SS), Serial Clock(SCLK), MOSI(Master Out Slave

In), MISO(Master In Slave Out).

The SPI protocol defines four modes for its operation (Mode 0, 1, 2, 3). Each mode differs

according to the SCLK polarity and phase - how the polarity and phase control the flow of

data on the SPI bus.

The W5100 operates as SPI Slave device and supports the most common mode - SPI Mode 0.

With SPI Mode 0, data is always latched in on the rising edge of SCLK and always output on

the falling edge of SCLK.

6.3.2 Commands

According to SPI protocol, there are only two data lines used between SPI devices. So, it is

necessary to define OP-Code. W5100 uses two types of OP-Code - Read OP-Code and Write

OP-Code. Except for those two OP-Codes, W5100 will be ignored and no operation will be

started.

In SPI Mode, W5100 operates in “unit of 32-bit stream”.

The unit of 32-bit stream is composed of 1 byte OP-Code Field, 2 bytes Address Field and 1

byte data Field.

OP-Code, Address and data bytes are transferred with the most significant bit(MSB) first and

least significant bit(LSB) last. In other words, the first bit of SPI data is MSB of OP-Code Field

and the last bit of SPI data is LSB of Data-Field. W5100 SPI data format is as below.

Command

OP-Code Field

Address Field

Data Field

Write operation

0xF0

1111 0000

2 bytes

1 byte

Read operation

0x0F

0000 1111

2 bytes

1 byte

W5100 Datasheet(PDF) 63 Page - WIZnet Co., Ltd