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Programming Model
Bit
31–30
29–28
27–23
22–18
17–16
15–0
To perform a read or write operation on the MII Management Interface, the MMFR register
must be written by the user. To generate a valid read or write management frame, the ST
field must be written with a 01 pattern, and the TA field must be written with a 10. If other
patterns are written to these fields, a frame will be generated but will not comply with the
IEEE 802.3 MII definition.
To generate an IEEE 802.3-compliant MII Management Interface write frame (write to a
PHY register), the user must write {01 01 PHYAD REGAD 10 DATA} to the MMFR
register. Writing this pattern will cause the control logic to shift out the data in the MMFR
register following a preamble generated by the control state machine. During this time the
contents of the MMFR register will be altered as the contents are serially shifted and will
be unpredictable if read by the user. Once the write management frame operation has
completed, the MII interrupt will be generated. At this time the contents of the MMFR
register will match the original value written.
To generate an MII Management Interface read frame (read a PHY register) the user must
write {01 10 PHYAD REGAD 10 XXXX} to the MMFR register (the content of the DATA
field is a don't care). Writing this pattern will cause the control logic to shift out the data in
the MMFR register following a preamble generated by the control state machine. During
this time the contents of the MMFR register will be altered as the contents are serially
shifted, and will be unpredictable if read by the user. Once the read management frame
operation has completed, the MII interrupt will be generated. At this time the contents of
the MMFR register will match the original value written except for the DATA field whose
contents have been replaced by the value read from the PHY register.
17-30
Table 17-17. MMFR Field Descriptions
Name
ST
Start of frame delimiter. These bits must be programmed to 01
for a valid MII management frame.
OP
Operation code. This field must be programmed to 10 (read) or
01 (write) to generate a valid MII management frame. A value
of 11 will produce "read" frame operation while a value of 00 will
produce "write" frame operation, but these frames will not be MII
compliant.
PA
PHY address. This field specifies one of up to 32 attached PHY
devices.
RA
Register address. This field specifies one of up to 32 registers
within the specified PHY device.
TA
Turn around. This field must be programmed to 10 to generate
a valid MII management frame.
DATA
Management frame data. This is the field for data to be written
to or read from the PHY register.
MCF5282 User's Manual
Description
MOTOROLA
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