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14.5.7
FEC MII Management Frame Register—MBAR + 0x3040
This MII_DATA register does not reset to a defined value. The MII_DATA register is used to communicate with the attached MII compatible
PHY device(s), providing read/write access to the MII registers.
Writing to the MII_DATA register causes a management frame to be sourced unless the MII_SPEED register has been programmed to 0. When
writing to MII_DATA when MII_SPEED = 0, if the MII_SPEED register is then written to a non-zero value, an MII frame is generated with
the data previously written to the MII_DATA register. This let MII_DATA and MII_SPEED be programmed in either order if MII_SPEED is
currently 0.
msb 0
1
R
ST
W
RESET:
X
X
16
17
R
W
RESET:
X
X
Note: X: Bit does not reset to a defined value.
Bits
Name
0:1
ST
2:3
OP
4:8
PA
9:13
RA
14:15
TA
16:31
DATA
To do a read or write operation the MII management interface writes to the MII_DATA register. To generate a valid read or write management
frame:
•
the ST field must be written with a 01
•
the OP field must be written with either:
— 01 (management register write frame), or
— 10 (management register read frame), and
•
the TA field must be written with a 10
If other patterns are written to these fields, a frame is generated, but it does not comply to the IEEE 802.3 MII definition:
•
OP field = 1x produces a "read" frame operation, while
•
OP field = 0x produces a "write" frame operation.
To generate an IEEE 802.3 compliant MII management interface write frame (write to a PHY register), the user must write the following to
the MII_DATA register:
{01 01 PHYAD REGAD 10 DATA}
Writing this pattern causes control logic to shift out the data in the MII_DATA register following a preamble generated by the control state
machine. During this time, the MII_DATA register contents are altered as the contents are serially shifted, and is unpredictable if read by the
Freescale Semiconductor
Table 14-15. FEC MII Management Frame Register
2
3
4
5
6
OP
PA
X
X
X
X
X
18
19
20
21
22
X
X
X
X
X
Start of Frame Delimiter—bits must be programmed to 01 for a valid MII management frame.
Operation Code—field must be programmed to 10 (read) or 01 (write) to generate a valid MII
management frame.
• A value of 11 causes a "read" frame operation.
• A value of 00 causes a "write" frame operation. However, these frames are not MII
compliant.
PHY Address—specifies 1 of up to 32 attached PHY devices.
Register Address—specifies 1 of up to 32 registers within the specified PHY device.
TurnAround—must be programmed to 10 to generate a valid MII management frame.
Management Frame Data—used for data written to or read from PHY register.
MPC5200B Users Guide, Rev. 1
7
8
9
10
11
RA
X
X
X
X
23
24
25
26
27
DATA
X
X
X
X
Description
FEC Registers—MBAR + 0x3000
12
13
14
15
TA
X
X
X
X
X
28
29
30
31 lsb
X
X
X
X
X
14-17
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