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UM10360_0
© NXP B.V. 2009. All rights reserved.
User manual
Rev. 00.06 — 5 June 2009
117 of 808
NXP Semiconductors
UM10360
Chapter 10: LPC17xx Ethernet
Support for IEEE 802.3/clause 31 flow control is implemented in the flow control block.
Receive flow control frames are automatically handled by the MAC. Transmit flow control
frames can be initiated by software. In half duplex mode, the flow control module will
generate back pressure by sending out continuous preamble only, interrupted by pauses
to prevent the jabber limit from being exceeded.
The Ethernet block has a standard Reduced Media Independent Interface (RMII) to
connect to an external Ethernet PHY chip. Registers in the PHY chip are accessed via the
AHB interface through the serial management connection of the MIIM bus, typically
operating at 2.5 MHz.
8.2 Example PHY Devices
Some examples of compatible PHY devices are shown in
9.
Pin description
shows the signals used for connecting the Reduced Media Independent
Interface (RMII) to the external PHY.
shows the signals used for Media Independent Interface Management
(MIIM) of the external PHY.
Table 103. Example PHY Devices
Manufacturer
Part Number(s)
Broadcom
BCM5221
ICS
ICS1893
Intel
LXT971A
LSI Logic
L80223, L80225, L80227
Micrel
KS8721
National
DP83847, DP83846, DP83843
SMSC
LAN83C185
Table 104. Ethernet RMII pin descriptions
Pin Name
Type
Pin Description
ENET_TX_EN
Output
Transmit data enable
ENET_TXD[1:0]
Output
Transmit data, 2 bits
ENET_RXD[1:0]
Input
Receive data, 2 bits.
ENET_RX_ER
Input
Receive error.
ENET_CRS
Input
Carrier sense/data valid.
ENET_REF_CLK/
ENET_RX_CLK
Input
Reference clock
Table 105. Ethernet MIIM pin descriptions
Pin Name
Type
Pin Description
ENET_MDC
Output
MIIM clock.
ENET_MDIO
Input/Output
MI data input and output