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Intel
®
IXP45X and Intel
®
IXP46X Product Line of Network Processors—Ethernet MACs
Intel
®
IXP45X and Intel
®
IXP46X Product Line of Network Processors
Developer’s Manual
August 2006
232
Order Number: 306262-004US
The MDIO Status Register is broken into four 8-bit registers. The data returned from
the physical interface will be captured in MDIO Status 0 (MDIOSTS0) Register and
MDIO Status 1 (MDIOSTS1) Register:
• MDIO Status 0 (MDIOSTS0) Register corresponds to bits (7:0) of the MDIO Status
(MDIOSTS) Register.
• MDIO Status 1 (MDIOSTS1) Register corresponds to bits (15:8) of the MDIO Status
(MDIOSTS) Register.
• Bits (30:16) of the MDIO Status (MDIOSTS) Register are reserved and will return
zeros when read.
• Bit 31 of the MDIO Status (MDIOSTS) Register will indicate the condition of the
read.
— If logic 1 is read from bit 31 of the MDIO Status (MDIOSTS) Register after a
read transaction from the physical interface is complete, the read contained an
error and should be disregarded.
— If logic 0 is read from bit 31 of the MDIO Status (MDIOSTS) Register after a
read transaction from the physical interface is complete, the read was valid and
error free.
shows an example of the data being read from the physical interface (PHY)
by the xMII Management Master (IXP45X/IXP46X network processors) using the MDIO
interface. These registers should be manipulated using Intel-supplied APIs.
Figure 30.
MDIO Write
Notes:
1.
ST (Start Bits) is a signal that is logic 0 followed by logic 1 after a PREAMBLE stage.
2.
OC (Op Code) is a two-bit signal that informs the destination PHYs if the current requested transaction is a read or a
write. Logic0 followed by logic 1 indicates a write transaction is requested. Logic 1 followed by logic 0 indicates a read
transaction.
3.
TA (Turn Around) is a two-bit, turn-around time used to allow the control of the MDIO to change directions. For write
operations, the TA bits will be logic 1 followed by logic 0. For read transactions, the TA bits will be high-impedance (Z)
followed by the selected PHY driving the MDIO signal with logic 0.
4.
For write operations, the Management Interface Master will drive the MDIO signal for the duration of the access.
5.
For read operation, the Management Interface Master will drive the MDIO signal until the turn around cycle. The PHY will
drive the MDIO signal for the second bit of the turn around and the remaining 16 data bits.
MDC
MDIO
PHY ADDR
(4:0)
REG ADDR
(4:0)
MDIOCMD2
(7:0)
MDIOCMD1
(7:0)
PREAMBLE
32 consecutive 1s
ST
OC
TA
4 3 2 1 0 4 3 2 1
15 14 13 12 1110 9 8 7 6 5 4 3 2 1 0
0
B2171-01