CS8952T-CQ Cirrus Logic, CS8952T-CQ Datasheet - Page 26

• Manufacturer Part Number: CS8952T-CQ
• Description: 100BASE E-X AND 10BASE-T TRANSCEIVER
• Manufacturer: Cirrus Logic

Transmission and/or reception of each byte of data
is done one nibble at a time in the following order:
MII Receive Data
The presence of recovered data on the RXD[3:0]
bus is indicated by the assertion of RX_DV.
RX_DV will remain asserted from the beginning of
the preamble (or Start of Frame Delimiter if pream-
ble is not used) to the End of Frame Delimiter.
Once RX_DV is asserted, valid data will be driven
onto RXD[3:0] synchronously with respect to
RX_CLK.
26
RXD[3:0]
RXD[3:0]
RX_CLK
RX_CLK
MII
Nibble
Stream
RX_DV
RX_ER
RX_DV
RX_ER
First Bit
MSB
LSB
First
Nibble
LSB
D0
D1
D2
D3
D0
D1 D2 D3 D4 D5 D6 D7
MAC’s Serial Bit Stream
Preamble
Preamble
CIRRUS LOGIC ADVANCED PRODUCT DATABOOK
SFD
SFD
Figure 2. Reception without errors
Figure 3. Reception with errors
Second
Nibble
SFD
SFD
MSB
Data
Data
CrystalLAN™ 100BASE-X and 10BASE-T Transceiver
Data
Data
Receive errors are indicated during frame reception
by the assertion of RX_ER. It indicates that an er-
ror was detected somewhere in the frame currently
being transferred across the MII. RX_ER will tran-
sition synchronously with respect to the RX_CLK,
and will be held high for one cycle for each error
received. It is up to the MAC to ensure that a CRC
error is detected in that frame by the Logical Link
Control. Figure 2 illustrates reception without er-
rors, and Figure 3 illustrates reception with errors.
MII Transmit Data
TX_EN is used by the MAC to signal to the
CS8952T that valid nibbles of data are being pre-
sented across the MII via TXD[3:0]. TX_EN must
be asserted synchronously with the first nibble of
preamble, and must remain asserted as long as val-
id data is being presented to the MII.
TX_EN must be de-asserted within one TX_CLK
cycle after the last nibble of data (CRC) has been
presented to the CS8952T. When TX_EN is not as-
serted, data on TXD[3:0] is ignored.
Data
Data
Error
Data
Data
XX
XX
CRC
XX
DS206TPP2
CS8952T