Freescale Semiconductor MPC5748G User Manual page 21

For MII mode (default) R45 should have a jumper populated as shown. For RMII mode, remove R45
and fit it between R45 and R80
For RMII mode
remove R45 and re-fit
in this position
To change the reset routing so that the Ethernet PHY can be reset via MCU pin PI11 (rather than being
tied to the MCU reset), jumper J8 should be moved to position 2-3
Table 14. Ethernet Control jumpers (J5, J6, J7, J8, R45, R80)
Jumper Position
1-2 (D)
J5
2-3
Removed
1-2 (D)
J6
(X1)
2-3
1-2 (D)
J7
2-3
(X2)
Removed
1-2 (D)
J8
2-3
(RST)
Removed
Fitted R45
R45 (R80)
R45 to R80
The MCU Ethernet signals are all in the VDD_HV_B domain. The Ethernet PHY will ONLY function
with 3.3V I/O so VDD_HV_B must be set to 3.3V on the MCU daughtercard before the Ethernet is
used. If VDD_HV_B is set to 5V, the signals routed to the Ethernet PHY (see the EVB schematics) must
be left as tristate.
5
If jumper J7 is in position 1-2 (25MHz XTAL), J6 must be fitted and R45 must be fitted.
6
If jumper J7 is in position 2-3 (50MHz oscillator), J6 must be removed and R45 must be removed and placed
between R45 and R80
Freescale Semiconductor, Inc.
Figure 11. MII / RMII Clock Selection Resistor
PCB Legend Description
MII Ethernet PHY is configured in MII mode
R Ethernet PHY is configured in RMII mode
Invalid Configuration, avoid!
Ethernet PHY X2 clock is connected to 25MHz xtal
Ethernet PHY X2 clock is not connected to 25MHz xtal
Ethernet PHY X1 clock is connected to 25MHz xtal
Ethernet PHY X1 clock is driven from 50MHz xtal
Ethernet PHY X1 clock is disconnected (invalid configuration, avoid)
NORM The Ethernet PHY will be reset along with MCU reset
PI11
The Ethernet PHY reset is controlled via MCU pin PI11 (Pulled high)
Invalid Configuration, avoid!
MII Mode – Clock is supplied from PHY to MCU
RMII Mode – Clock is supplied from external 50MHz oscillator to MCU
MPC5748G EVB User Guide, User Guide, Rev. 0, 08/2015
Communications & Memory Interfaces:
5 6
,
21