VSC8540XMVRT-HC datasheet(15/87 Pages) MICROCHIP

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DS60001603E-page 15

VSC8540RT

5.0

FUNCTIONAL DESCRIPTIONS

This section describes the functional aspects of the VSC8540RT device, including available configurations, operational

features, and testing functionality. It also defines the device setup parameters that configure the device for a particular

application.

5.1

Operating Modes

The following table lists the operating modes of the VSC8540RT device.

5.2

MAC Interface

The VSC8540RT device supports RMII version 1.2, RGMII versions 1.3 and 2.0, and MII MAC interfaces at 1.5V, 1.8V,

2.5V, and 3.3V operating voltages. In order to help reduce EMI, the VSC8540RT device also includes edge rate pro-

grammability for the MAC interface signals through register 27E2.7:5.

The recommended values for RS resistor (as shown in Figure 5-1, Figure 5-4, and Figure 5-5) are listed in the following

table.

Refer to the MAC datasheet for the value to use for RT resistor.

5.2.1

RGMII MAC INTERFACE MODE

The VSC8540RT device supports RGMII versions 1.3 and 2.0 (without HSTL modes). The RGMII interface supports

10 Mbps and 100 Mbps speeds, and is used as an interface to a RGMII-compatible MAC. The device is compliant with

the RGMII interface specification when VDDMAC is operating at 2.5V. While the RGMII specification only specifies oper-

ation at 2.5V, the device can also support the RGMII interface at 1.5V, 1.8V, and 3.3V.

FIGURE 5-1:

RGMII MAC INTERFACE

TABLE 5-1:

OPERATING MODES

Operating Mode

Supported Media

RGMII-Cat5

10/100BASE-TX

MII-Cat5

10/100BASE-TX

RMII-Cat5

10/100BASE-TX

TABLE 5-2:

RECOMMENDED VALUES FOR RS (± 5%)

VDDMAC Value

RS Value

1.5 V



1.8V



2.5V



3.3V



RGMII MAC

TXD[3]

TXD[2]

TXD[1]

TXD[0]

RXD[3]

RXD[2]

RXD[1]

RXD[0]

TX_CLK

TX_CTL

RX_CLK

RX_CTL

SimpliPHY

TXD[3]

TXD[2]

TXD[1]

TXD[0]

RXD[3]

RXD[2]

RXD[1]

RXD[0]

GTX_CLK

TX_CTL

RX_CLK

RX_CTL

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