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278 Software Developer’s Manual
Register Descriptions
13.4.7.1.26 MDI Register 30 Access Window
1
R30AW (30d; R/W)
13.4.7.1.27 Documented MDI Register 30 Operations
1
Unless otherwise specified, no reset operations are required in order for the following operations to
take effect.
NOTE: Any time the PHY is reset it returns to Class AB drive mode.
Table 13-50. MDI Register 30 Page Select Bit Description
Field Bit(s) Description Mode HW Rst SW Rst
Register 30 Access 15:0
Provides read/write capability for
register selected via MDI register 29.
R/W 0000h 0000h
1. Not applicable to the 82544GC/EI, 82541xx, or 82547GI/EI.
Table 13-51. MDI Register 30 Operations
To Perform Operation MDI Read/Write Sequence
Power down SerDes (optimize
power for copper PHY operation)
1
1. Not applicable to 82540EP/EM
30_31.15:0 <= x2001h
• Write MDI register 29 <= 31d
• Write MDI register 30 <= 2001h
Tune VCO on SerDes Rx for
optimal Bit Error Ratio (BER)
1
30_5.8 <= 0b
30_4.11 <= 1b
• Write MDI register 29 <= 5d
• Read MDI register 30
• Change bit 8 to 0
• Write result to MDI register 30
• Write MDI register 29 <= 4d
• Read MDI register 30
• Change bit 11 to 1
• Write result to MDI register 30
Set PHY output drivers into Class A
mode (Class AB is default after
reset)
30_11.15:0 = 8004h
• Write MDI register 29 = 11d
• Write MDI register 30 = 8004h