Beckhoff EtherCAT Technology Section I Manual de usuario descargar pdf (Pagina 49)

Ethernet Physical Layer

Slave Controller – Technology I-29

5.10.3 MI Protocol

Each MI access begins with a Preamble of “Ones“(32 without preamble suppression, less if both ESC

and PHY support preamble suppression), followed by a Start-of-Frame (01) and the Operation Code

(01 for write and 10 for read operations). Then the PHY address (5 bits) and the PHY register address

(5 bits) are transmitted to the PHY. After a Turnaround (10 for write and Z0 for read operations – Z

means MDIO is high impedance), two bytes of data follow. The transfer finishes after the second data

byte and at least one IDLE cycle.

5.10.4 Timing specifications

Table 18: MII Management Interface timing characteristics

Parameter

Comment

Clk

MDC period

Write

Write access time

Read

Read access time

1 0 1

1 0

MDC

MDIO

Clk

A4 A2A4 A1 R4A0 R3 R2

Preamble PHY Address

D7 D5D6 D4 D2D3 D1 D0

High Data Byte Low Data Byte

MDC

MDIO

Write

Start OP code

R1 R0

PHY Register Address

Turnaround

D15 D13D14 D12 D10D11 D9 D8

Write

IDLE

Figure 8: Write access

1 1 00

MDC

MDIO

Clk

A4 A2A4 A1 R4A0 R3 R2

Preamble PHY Address

D7 D5D6 D4 D2D3 D1 D0

High Data Byte Low Data Byte

MDC

MDIO

Read

Start OP code

R1 R0

PHY Register Address

Turn-

around

D15 D13D14 D12 D10D11 D9 D8

Read

IDLE

Figure 9: Read access

1 2 ... 44 45 46 47 48 49 50 51 52 53 54 ... 115 116

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