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Fast Ethernet Controller (FEC)
MPC5566 Microcontroller Reference Manual, Rev. 2
15-18
Freescale Semiconductor
The MII_SPEED field must be programmed with a value to provide an MDC frequency of less than or
equal to 2.5 MHz to be compliant with the IEEE
®
802.3 MII specification. The MII_SPEED must be set
to a non-zero value in order to source a read or write management frame. After the management frame is
complete, the MSCR register can be optionally cleared to zero to turn off the MDC. The MDC generated
has a 50% duty cycle except when MII_SPEED is changed during operation (the change takes effect
following a rising- or falling-edge of MDC).
If the system clock is 50 MHz, programming this register to 0x0000_0005 results in an MDC frequency
of 50 MHz
x
1/20 = 2.5 MHz. A table showing optimum values for MII_SPEED as a function of system
clock frequency is provided in
15.3.4.2.8
MIB Control Register (MIBC)
The MIBC is a read/write register used to provide control of and to observe the state of the MIB block.
This register is accessed by the application if there is a need to disable the MIB block operation. For
example, in order to clear all MIB counters in RAM the application must disable the MIB block, then clear
all the MIB RAM locations, then enable the MIB block. The MIB_DISABLE bit is reset to 1. See
for the locations of the MIB counters.
25–30
MII_SPEED
MII_SPEED controls the frequency of the MII management interface clock (FEC_MDC) relative to the
system clock. A value of 0 in this field “turns off” the MDC and leaves it in a low voltage state. Any
non-zero value results in the MDC frequency of 1
÷
(MII_SPEED
×
4) of the system clock frequency.
31
Reserved, must be cleared.
Table 15-11. Programming Examples for MSCR
System Clock Frequency
MII_SPEED (field in reg)
MDC frequency
50 MHz
0x0005
2.5 MHz
66 MHz
0x0007
2.36 MHz
80 MHz
0x0008
2.5 MHz
100 MHz
0x000A
2.5 MHz
132 MHz
0x000D
2.5 MHz
Table 15-10. MSCR Field Descriptions
Field
Description
Summary of Contents for MPC5566
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Page 135: ...Signal Description MPC5566 Microcontroller Reference Manual Rev 2 2 54 Freescale Semiconductor...
Page 189: ...Reset MPC5566 Microcontroller Reference Manual Rev 2 4 20 Freescale Semiconductor...
Page 603: ...Flash Memory MPC5566 Microcontroller Reference Manual Rev 2 13 38 Freescale Semiconductor...
Page 609: ...SRAM MPC5566 Microcontroller Reference Manual Rev 2 14 6 Freescale Semiconductor...
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