DP83848YB_08 NSC [National Semiconductor], DP83848YB_08 Datasheet - Page 23
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DP83848YB_08
Manufacturer Part Number
DP83848YB_08
Description
Manufacturer
NSC [National Semiconductor]
Datasheet
1.DP83848YB_08.pdf
(84 pages)
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3.4.3 Serial Management Preamble Suppression
The DP83848YB supports a Preamble Suppression mode
as indicated by a one in bit 6 of the Basic Mode Status
Register (BMSR, address 01h.) If the station management
entity (i.e. MAC or other management controller) deter-
mines that all PHYs in the system support Preamble Sup-
pression by returning a one in this bit, then the station
management entity need not generate preamble for each
management transaction.
The DP83848YB requires a single initialization sequence
of 32 bits of preamble following hardware/software reset.
Read Operation
Write Operation
MII Management
MDIO
MDIO
MDC
MDC
MDIO
Serial Protocol
(STA)
(PHY)
(STA)
Z
Idle
Z
Idle
Z
Z
0
0
Start
Start
1 1
1
Opcode
(Read)
Opcode
(Write)
0
0 0
1
0
(PHYAD = 0Ch)
(PHYAD = 0Ch)
PHY Address
PHY Address
1 1 0 0 0 0 0 0 0
1 1 0 0 0 0 0 0 0
<idle><start><op code><device addr><reg addr><turnaround><data><idle>
Figure 5. Typical MDC/MDIO Write Operation
Figure 4. Typical MDC/MDIO Read Operation
<idle><01><10><AAAAA><RRRRR><Z0><xxxx xxxx xxxx xxxx><idle>
<idle><01><01><AAAAA><RRRRR><10><xxxx xxxx xxxx xxxx><idle>
Table 5. Typical MDIO Frame Format
Register Address
Register Address
(00h = BMCR)
(00h = BMCR)
Z
Z
Z
23
1
TA
0 0 0 1 1 0 0 0 1 0 0 0 0 0 0 0 0
TA
This requirement is generally met by the mandatory pull-up
resistor on MDIO in conjunction with a continuous MDC, or
the management access made to determine whether Pre-
amble Suppression is supported.
While the DP83848YB requires an initial preamble
sequence of 32 bits for management initialization, it does
not require a full 32-bit sequence between each subse-
quent transaction. A minimum of one idle bit between man-
agement transactions is required as specified in the IEEE
802.3u specification.
0 0 0
0 0
0 0 0
Register Data
Register Data
0
0 0 0 0 0 0 0 0
www.national.com
Z
Idle
Z
Z
Idle
Z
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