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____________________________________________________ DS34T101, DS34T102, DS34T104, DS34T108
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interface. It is used during auto negotiation to ensure that the MAC and the PHY are configured for the same speed
and duplex configuration.
The PHY maintenance register is implemented as a shift register. Writing to the register starts a shift operation
3
MAC_network_status register (about 2000
CLK_SYS cycles later). An interrupt is generated as this bit is set. During this time, the MSB of the
register is output on the
MDIO pin and the LSB is updated from the
MDIO pin with each
MDC cycle. In this way a
PHY management packet is transmitted on MDIO. See Section 22.2.4.5 of the IEEE 802.3 standard. Reading
during the shift operation (not recommended) returns the current contents of the shift register.
At the end of the shift operation, the bits have shifted back to their original locations. For a read operation, the data
bits are updated with data read from the PHY. It is important to write the correct values to the register to ensure a
valid PHY management packet is produced.
MAC_PHY_maintenance 0x034
Bits
Data Element Name
R/W
Reset
Value
Description
[31:30]
Start_of_packet
R/W
0x0
Must be written 01 for a valid packet
[29:28]
Operation
R/W
0x0
00 = Reserved
01 = Write
10 = Read
11 = Reserved
[27:23]
PHY_address
R/W
0x0
Specifies the PHY to access
[22:18]
Register_address
R/W
0x0
Specifies the register in the PHY to access
[17:16]
Must_be_written_to_10
R/W
0x0
Read as written
[15:0]
PHY_data
R/W
0x0000
For a write operation this field is the data to be written to
the PHY. After a read operation this field contains the data
read from the PHY
MAC_pause_time 0x038
Bits
Data Element Name
R/W
Reset
Value
Description
[31:16]
Reserved
RO
0x0000
Read 0, ignored on write
[15:0]
Pause time
RO
0x0000
Stores the current value of the pause time register, which
is decremented every 512 bit times.
MAC_specific_address_lower 0x098
Bits
Data Element Name
R/W
Reset
Value
Description
[31:0]
MAC Specific Address [31:0]
R/W
0x0
Least significant bits of the MAC specific address, i.e. bits
31:0. This field is used for transmission of pause packets
MAC_specific_address_upper 0x09C
Bits
Data Element Name
R/W
Reset
Value
Description
[31:16]
Reserved
RO
0x0000
Read 0, ignored on write
[15:0]
MAC Specific Address [47:32]
R/W
0x0000
Most significant bits of the MAC specific address, i.e. bits