Freescale Semiconductor POWERPC MPC860T - Manual (Page 45)

MOTOROLA Chapter 6. Programming Model 6-13
PRELIMINARYÑSUBJECT TO CHANGE WITHOUT NOTICE
Table 6-14 describes MII_DATA Þelds.
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.
To generate an 802.3-compliant MII management interface write frame (write to a PHY
register) the user must write {01 01 PHYAD REGAD 10 DATA} to MII_DATA. Writing
this pattern causes the control logic to shift data out of MII_DATA following a preamble
generated by the control state machine. When the write management frame operation
completes, the MII_DATAIO_COMPL interrupt is generated. At this time the contents of
MII_DATA 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 MII_DATA, (the content of the DATA Þeld
is a donÕt care). Writing this pattern causes the control logic to shift data out of MII_DATA
following a preamble generated by the control state machine. During this time, the contents
of MII_DATA are serially shifted and are unpredictable if read by the user. An
MII_DATAIO_COMPL interrupt is generated when the read management frame operation
Bits 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15
Field ST OP PA RA TA
Reset UndeÞned
R/W Read/write
Addr 0xE80
Bits 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31
Field DATA
Reset UndeÞned
R/W Read/write
Addr 0xE82
Figure 6-13. MII_DATA Register
Table 6-14. MII_DATA Field Descriptions
Bits Name Description
0Ð1 ST Start of frame delimiter. Must be programmed to 01 for a valid MII management frame.
2Ð3 OP Operation code. Must be 10 (read) or 01(write) to generate a valid MII management frame.
4Ð8 PA PHY address. SpeciÞes one of up to 32 attached PHY devices.
9Ð13 RA Register address. SpeciÞes one of up to 32 registers within the speciÞed PHY device.
14Ð15 TA Turnaround. Must be programmed to 10 to generate a valid MII management frame.
16Ð31 DATA Management frame data. Field for data to be written to or read from PHY register.
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