LH79524/LH79525 User’s Guide
Ethernet MAC Controller
Version 1.0
6-35
6.3.2.12 PHY Maintenance Register (PHYMAINT)
This register enables the EMAC to communicate with a PHY by means of the MDIO inter-
face. It is used during auto negotiation to ensure that the EMAC and the PHY are config-
ured 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, which is signalled as complete when bit two is set in the
NETSTATUS register, about 2,000 HCLK cycles later. An interrupt is also generated.
During this time, the MSB of the register is output on the ETHERMDIO pin and the LSB
updated from the ETHERMDIO pin with each ETHERMDC cycle. This causes transmis-
sion of a PHY management frame on ETHERMDIO. See Section 22.2.4.5 of the IEEE
802.3 standard.
Reading during the shift operation will return the current contents of the shift register. At
the end of management operation, the bits will have shifted back to their original locations.
For a read operation, the data bits will be updated with data read from the PHY.
Table 6-28. PHYMAINT Register
BIT
31
30
29
28
27
26
25
24
23
22
21
20
19
18
17
16
FIELD
STARTFRM
OP
ERA
T
ION
PHYADDR
REGADDR
///
RESET
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
TYPE
RW
RW
RW
RW
RW
RW
RW
RW
RW
RW
RW
RW
RW
RW
RW
RW
BIT
15
14
13
12
11
10
9
8
7
6
5
4
3
2
1
0
FIELD
PHYRDWR
RESET
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
TYPE
RW
RW
RW
RW
RW
RW
RW
RW
RW
RW
RW
RW
RW
RW
RW
RW
ADDR
0xFF 0x34
Table 6-29. PHYMAINT Fields
BITS
NAME
FUNCTION
31:30
STARTFRM
Start Of Frame
Must be written 0b01 for a valid frame.
29:28 OPERATION
Operation
00 = Invalid
01 = Write
10 = Read
11 = Invalid
27:23
PHYADDR
Phy Address
The PHY address is written to this field.
22:18
REGADDR
Register Address
Specifies the address of the register in the PHY
to access.
17:16
///
Must be written with 0b10. Reads the value written.
15:0
PHYRDWR
PHY Read or Write Data
The data to be written to the PHY is contained in
these two bytes. For a read, this contains the two bytes read from the PHY.