VSC8541-01 datasheet(21/100 Pages) MICROSEMI

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Functional Descriptions

VMDS-10496 VSC8541-01 Datasheet Revision 4.2

one of 4 possible combinations through this external strapping option to provide a total of 4 PHY

addresses in unmanaged operation.

3.3.4

GMII/MII or RGMII/RMII MAC Interface Mode

When MII_TXCLK pin is pulled LOW externally and the state of that signal is latched to logic 0 on the

rising edge of reset, the device operates in a RGMII mode. When MII_TXCLK pin is pulled HIGH

externally and the state of that signal is latched to logic 1 on the rising edge of reset, the device operates

in GMII/MII mode (depending on link speed). This signal is bonded out to a package pin.

Note: If unmanaged mode is selected and Signal E is latched as a logic 1 (indicating RMII mode), the device

will default to RMII mode regardless of the latched state of the MII_TXCLK.

3.3.5

CLKOUT Frequency Selection

The RXD6 and RXD7 pins can be pulled LOW or HIGH externally to set the bit 0 and bit 1 default values

of the CLKOUT frequency selection register 13G.14:13. The following table describes the allowed default

CLKOUT frequency settings.

The CLKOUT frequency can be changed from the default setting to any of the other settings on any

device variant by modifying the register bits through the SMI interface.

3.3.6

Forced 1000BASE-T Mode

When RX_ER pin is pulled high externally and the state of that signal is latched to logic 1 on the rising

edge of reset, the device operates in a Forced 1000BT mode. When this mode is enabled, the state of

pins COL and CRS are latched on the rising edge of reset to configure Master/Slave and MDI/MDI-X,

respectively. The latched state of the COL pin configures the device in Master mode when it is logic 1,

and in Slave mode when it is logic 0. The latched state of the CRS pin configures the device in MDI mode

when it is logic 0 and in MDI-X mode when it is logic 1.

3.4

Cat5 Twisted Pair Media Interface

The twisted pair interface is compliant with IEEE 802.3-2008 and the IEEE 802.3az-2010 standard for

Energy-Efficient Ethernet.

3.4.1

Voltage Mode Line Driver

The VSC8541-01 device uses a patented voltage mode line driver that allows it to fully integrate the

series termination resistors that are required to connect the PHY’s Cat5 interface to an external 1:1

transformer. The interface does not require the user to place an external voltage on the center tap of the

magnetic. The following figure illustrates the connections.

Table 10 •

CLKOUT Frequency Selection

CLKOUT Frequency Selection CLKOUT Frequency

25 MHz

50 MHz

125 MHz

Reserved

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