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MDIO Registers
4.12 MDIO User Access Register 0 (USERACCESS0)
The MDIO user access register 0 (USERACCESS0) is shown in Figure 26 and described in Table 25.
Figure 26. MDIO User Access Register 0 (USERACCESS0)
31 | 30 | 29 | 28 | 26 | 25 | 21 | 20 | 16 |
GO | WRITE | ACK |
| Reserved |
| REGADR |
| PHYADR |
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15 |
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| 0 |
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| DATA |
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LEGEND: R = Read only; R/W = Read/Write; R/WS = Read/Write 1 to set; |
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Table 25. MDIO User Access Register 0 (USERACCESS0) Field Descriptions
Bit | Field | Value | Description |
31 | GO |
| Go bit. Writing a 1 to this bit causes the MDIO state machine to perform an MDIO access when it is |
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| convenient for it to do so; this is not an instantaneous process. Writing a 0 to this bit has no effect. |
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| This bit is writeable only if the MDIO state machine is enabled. This bit will self clear when the |
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| requested access has been completed. Any writes to the USERACCESS0 register are blocked |
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| when the GO bit is 1. |
30 | WRITE |
| Write enable bit. Setting this bit to a 1 causes the MDIO transaction to be a register write, otherwise |
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| it is a register read. |
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| 0 | The user command is a read operation |
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| 1 | The user command is a write operation |
29 | ACK |
| Acknowledge bit. This bit is set if the PHY acknowledged the read transaction. |
Reserved | 0 | Reserved | |
REGADR |
| Register address bits. This field specifies the PHY register to be accessed for this transaction | |
PHYADR |
| PHY address bits. This field specifies the PHY to be accesses for this transaction | |
DATA |
| User data bits. These bits specify the data value read from or to be written to the specified PHY | |
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| register. |
SPRU975B | Ethernet Media Access Controller (EMAC)/Management Data Input/Output (MDIO) | 77 |
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