Fast Ethernet Controller (FEC)
MPC885 PowerQUICC Family Reference Manual, Rev. 2
Freescale Semiconductor
45-23
The MII_DATA register, shown in
Figure 45-17
, is used to communicate with the attached MII-compatible
PHY device, providing read/write access to their MII registers. Writing to MII_DATA causes a
management frame to be sourced unless MII_SPEED was cleared; in this case, if MII_SPEED is then
written to a non-zero value and an MII frame is generated with the data previously written to MII_DATA.
This allows MII_DATA and MII_SPEED to be programmed in either order if MII_SPEED is currently
zero. MII_DATA is accessed by the user and does not reset to a defined value.
Table 45-20
describes MII_DATA fields.
To read or write on the MII management interface, MII_DATA is written by the user. To generate a valid
read or write management frame, ST must be 01, OP must be 01 (management register write frame) or 10
(management register read frame), and TA must be 10.
Table 45-19. X_DES_ACTIVE Field Descriptions
Bits
Name
Description
0–6
—
Reserved
7
X_DES_ACTIVE Set when this register is written, regardless of the value written. Cleared whenever no
additional ready descriptors remain in the transmit ring.
8–31
—
Reserved
0
1
2
3
4
8
9
13
14
15
Field
ST
OP
PA
RA
TA
Reset
Undefined
R/W
R/W
Addr
0x0E80 (FEC1) & 0x1E80 (FEC2)
16
31
Field
DATA
Reset
Undefined
R/W
R/W
Addr
0x0E82 (FEC1) & 0x1E82 (FEC2)
Figure 45-17. MII_DATA Register
Table 45-20. MII_DATA Field Descriptions
Bits
Name
Description
0–1
ST
Start of frame delimiter. Must be programmed to 01 for a valid MII management frame.
2–3
OP
Operation code. Must be 10 (read) or 01(write) to generate a valid MII management frame.
4–8
PA
PHY address. Specifies one of up to 32 attached PHY devices.
9–13
RA
Register address. Specifies one of up to 32 registers within the specified PHY device.
14–15
TA
Turnaround. Must be programmed to 10 to generate a valid MII management frame.
16–31
DATA
Management frame data. Field for data to be written to or read from PHY register.
Summary of Contents for PowerQUICC MPC870
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Page 1370: ...MPC880 MPC885 PowerQUICC Family Reference Manual Rev 2 E 4 Freescale Semiconductor ...
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