6.2 Ethernet Interfaces Signal Description
The 4450 is normally located in a system between a copper or fiber PHY and a Host's
GMAC. The network side of the 4450 functions like a MAC device and the host side
functions like a PHY. The host side interface provides six separate electrical signalling
options which include: GMII/TBI, RGMII/RTBI, SGMII, and SERDES. For the network side
interfaces, only RGMII/RTBI, SGMII and SERDES signalling options are available. GMII/TBI
signalling is not supported on the network side. The GMAC interfaces are capable of running
at 10/100/1000 speeds in either the GMII, RGMII or SGMII modes. The TBI, RTBI and
SERDES interfaces only support 1 Gbps speeds and will not run at 10/100 speeds. Note that
the 4450 is not designed to operate in asymmetric rate scenarios where for example the
host side is running at 1 Gbps and the network side at 10 Mbps.
Three configuration pins, host_config[2:0] are provided to select one of eight operating
configurations for the Host GMAC interfaces. The net_config[1:0] pins select one of four
operating configurations for the Network GMAC Interfaces. See Table 6-1 and Table 6-2 for
details on the GMAC Interface configurations.
Table 6-1. HOST Interface Modes
host_config[2:0]
Host Interfaces
RGMII
RTBI
MAC/PHY
MAC or PHY
MAC or PHY
MAC or PHY
MAC or PHY
MAC
000
001
010
011
100
101
110
111
SGMII
SerDes
GMII
GMII
PHY
TBI
MAC
TBI
PHY
Table 6-2. Network Interface Modes
net_config[1:0]
Network Interfaces
MAC/PHY
00
01
10
11
RGMII
RTBI
MAC or PHY
MAC or PHY
MAC or PHY
MAC or PHY
SGMII
SerDes
6.2.1
GMAC GMII/TBI Interface Usage (Host-side Only)
This section discusses the use of the Host Side GMAC interfaces h0 and h1 when configured
to support operation in GMII or TBI modes.
4450 – Data Sheet, DS-0131-06
Page33
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