CS8952T
CrystalLAN™ 100BASE-X and 10BASE-T Transceiver
erate without the preamble through bit 9 of the PCS
Sub-Layer Configuration Register (address 17h).
Preamble
Start of
Opcode
PHY
Register Turnaround
Data
Idle
(32 bits)
Frame
(2 bits)
Address
Address
(2 bits)
(16 bits)
(2 bits)
(5 bits)
(5 bits)
Table 6. MII Management Interface Frame Format
The Start of Frame is indicated by a 01 bit pattern.
A read transaction is indicated by an Opcode of 10
and a write by 01.
The PHY Address is five bits, with the most signif-
icant bit sent first. If the PHY address included in
the frame is not 00000 or does not match the PHY-
AD field of the Self Status Register (address 19h),
the rest of the frame is ignored.
The register address is five bits, with the most sig-
nificant bit sent first, and indicates the CS8952T
register to be written to/read from.
The Turnaround time is a two bit time spacing be-
tween when the MAC drives the last register ad-
dress bit onto MDIO and the data field of a
management frame in order to avoid contention
during a read transaction. For a read transaction,
the MAC should tri-state the MDIO pin beginning
on the first bit time, and the CS8952T will begin
driving the MDIO signal to a logic ZERO during
the second bit time. During write transactions,
since the MDIO direction does not need to be re-
versed, the MAC will drive the MDIO to a logic
ONE for the first bit time and a logic ZERO for the
second.
The data field is always 16 bits in length, with the
most significant bit sent first.
CIRRUS LOGIC ADVANCED PRODUCT DATABOOK
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DS206TPP2