BECKHOFF ET1100 - Manual (Page 32)

Pin Description
III-18 Slave Controller – ET1100 Hardware Description
3.2.6 Transparent Mode Enable
The ET1100 is capable of sharing the MII interfaces with other MACs on a per port basis. Typically,
the Transparent mode is disabled, and the ET1100 has exclusive access to the MII interfaces of the
PHYs. With the Transparent mode turned on, the MII interfaces can be assigned either to the ET1100
or to other MACs, e.g., µControllers with integrated MACs. Reassignment is not meant to be done
whilst network traffic is processed.
The Transparent mode primarily affects the PERR(x)/TRANS(x) signals. If Transparent mode is
enabled, PERR(x)/TRANS(x) becomes TRANS(x) (active low), which controls the transparent state of
each port. PERR(x) is not available in Transparent mode.
TRANS(x) does only affect the TX_ENA(x)/TX_D(x) signals of the same port as well as
MI_CLK/MI_DATA. RX_CLK(x), RX_DV(x), RX_D(x), and RX_ERR(x) are connected to both ET1100
and the other MAC.
Each MII interface behaves as usual as long as TRANS(x) is high, and the ET1100 controls the MII
interface. If TRANS(x) is low, the port becomes transparent (or isolated), i.e., the ET1100 will no
longer drive TX_ENA(x)/TX_D(x) actively, thus, the other MAC can drive these signals.
The Link/Act(x) LED will still be driven by the ET1100, because it samples RX_DV(x) and TX_ENA(x)
(which becomes an input while a port is transparent) for detection of activity.
As long as at least one MII interface is not transparent, the ET1100 is in control of the MII
management interface. With the Transparent mode turned on, the PHY management interface of the
ET1100 can be accessed via the PDI interface, so a µController gets access to the management
interface. If all MII interfaces are transparent, the ET1100 releases MI_CLK and MI_DATA drivers, so
they can be driven by the other MAC.
Refer to example schematics for more details.
Table 20: Transparent Mode Enable
Description Config signal Pin name Register Values
Transparent
Mode
Enable
TRANS_MODE_ENA
TX_D(1)[0]/
TRANS_MODE_ENA
0x0E01[3]
0 = normal mode/Transparent mode
disabled. ET1100 uses PHY exclusively
1 = Transparent mode enabled, ET1100
can share PHY with other MACs