gmacgrp_gmii_address

          Register 4 (GMII Address Register)  

The GMII Address register controls the management cycles to the external PHY through the management interface.

Note: This register is present for all PHY interface when you select the Station Management (MDIO) feature in coreConsultant.

Module Instance	Base Address	Register Address
`i_emac_emac0`	`0xFF800000`	`0xFF800010`
`i_emac_emac1`	`0xFF802000`	`0xFF802010`
`i_emac_emac2`	`0xFF804000`	`0xFF804010`

Offset: 0x10

Access: RW

Important: The value of a reserved bit must be maintained in software. When you modify registers containing reserved bit fields, you must use a read-modify-write operation to preserve state and prevent indeterminate system behavior.

Bit Fields
31	30	29	28	27	26	25	24	23	22	21	20	19	18	17	16
`reserved_31_16` `RO 0x0`
15	14	13	12	11	10	9	8	7	6	5	4	3	2	1	0
`pa` `RW 0x0`					`gr` `RW 0x0`					`cr` `RW 0x0`				`gw` `RW 0x0`	`gb` `RW 0x0`

gmacgrp_gmii_address Fields

Bit

Name

Description

Access

Reset

31:16

reserved_31_16

Reserved

RO

0x0

15:11

pa

Physical Layer Address

This field indicates which of the 32 possible PHY devices are being accessed.
For RevMII, this field gives the PHY Address of the RevMII module.

RW

0x0

10:6

gr

GMII Register

These bits select the desired GMII register in the selected PHY device.
For RevMII, these bits select the desired CSR register in the RevMII Registers set.

RW

0x0

5:2

cr

CSR Clock Range

The CSR Clock Range selection determines the frequency of the MDC clock according to the CSR clock frequency used in your design.

The suggested range of CSR clock frequency applicable for each value (when Bit[5] = 0) ensures that the MDC clock is approximately between the frequency range 1.0 MHz - 2.5 MHz.

0000: The frequency of the CSR clock is 60-100 MHz and the MDC clock is CSR clock/42.
0001: The frequency of the CSR clock is 100-150 MHz and the MDC clock is CSR clock/62.
0010: The frequency of the CSR clock is 20-35 MHz and the MDC clock is CSR clock/16.
0011: The frequency of the CSR clock is 35-60 MHz and the MDC clock is CSR clock/26.
0100: The frequency of the CSR clock is 150-250 MHz and the MDC clock is CSR clock/102.
0100: The frequency of the CSR clock is 250-300 MHz and the MDC clock is CSR clock/124.
0110 and 0111: Reserved

When Bit 5 is set, you can achieve MDC clock of frequency higher than the IEEE 802.3 specified frequency limit of 2.5 MHz and program a clock divider of lower value. For example, when CSR clock is of 100 MHz frequency and you program these bits as 1010, then the resultant MDC clock is of 12.5 MHz which is outside the limit of IEEE 802.3 specified range.

Program the following values only if the interfacing chips support faster MDC clocks:

1000: CSR clock/4
1001: CSR clock/6
1010: CSR clock/8
1011: CSR clock/10
1100: CSR clock/12
1101: CSR clock/14
1110: CSR clock/16
1111: CSR clock/18

These bits are not used for accessing RevMII. These bits are read-only if the RevMII interface is selected as single PHY interface.

Value	Description
0xa	DIV8
0xb	DIV10
0xc	DIV12
0xd	DIV14
0xe	DIV16AGAIN
0xf	DIV18
0x0	DIV42
0x1	DIV62
0x2	DIV16
0x3	DIV26
0x4	DIV102
0x5	DIV124
0x8	DIV4
0x9	DIV6

RW

0x0

gw

GMII Write

When set, this bit indicates to the PHY or RevMII that this is a Write operation using the GMII Data register. If this bit is not set, it indicates that this is a Read operation, that is, placing the data in the GMII Data register.

Value	Description
0x0	DISABLED
0x1	ENABLED

RW

0x0

gb

GMII Busy

This bit should read logic 0 before writing to Register 4 and Register 5. During a PHY or RevMII register access, the software sets this bit to 1'b1 to indicate that a Read or Write access is in progress.

Register 5 is invalid until this bit is cleared by the MAC. Therefore, Register 5 (GMII Data) should be kept valid until the MAC clears this bit during a PHY Write operation. Similarly for a read operation, the contents of Register 5 are not valid until this bit is cleared.

The subsequent read or write operation should happen only after the previous operation is complete. Because there is no acknowledgment from the PHY to MAC after a read or write operation is completed, there is no change in the functionality of this bit even when the PHY is not present.

Value	Description
0x0	DISABLED
0x1	ENABLED

RW

0x0