AM79C875KI AMD (ADVANCED MICRO DEVICES), AM79C875KI Datasheet - Page 15

• Manufacturer Part Number: AM79C875KI
• Manufacturer: AMD (ADVANCED MICRO DEVICES)

Specifications of AM79C875KI

• Lead Free Status / RoHS Status: Not Compliant

TXD[1:0]
Transmit Data
TXD[1:0] transitions synchronously with respect to
REF_CLK. When TX_EN is asserted, TXD[1:0] is ac-
cepted for transmission by the PHY. TXD[1:0] is
ignored by the PHY while TX_EN is deasserted.
TXD[1:0] in 100 Mbps Mode
TXD[1:0] provides valid data for each REF_CLK period
while TX_EN is asserted. Refer to Figure 3.
100BASE-X Block
The functions performed by the device include encod-
ing of MII 4-bit data (4B/5B), decoding of received code
groups (5B/4B), generating carrier sense and collision
detect indications, serialization of code groups for
transmission, de-serialization of serial data from recep-
tion, mapping of transmit, receive, and carrier sense at
the RMII interface, and recovery of clock from the in-
coming data stream. It offers stream cipher scrambling
and descrambling capability for 100BASE-TX applica-
tions.
I n t h e t r a n s m i t d a t a pa t h f o r 1 0 0 M b p s , t h e
NetPHY™ 4LP transceiver receives 2-bit wide data
across the RMII at 50 million di-bits per second. For
1 0 0 B A S E - T X a p p l i c a t i o n s , i t e n c o d e s a n d
REF_CLK
TX_EN
TXD[1]
TXD[0]
0
0
Di-Bit
Stream
0
1
TXD[0]/RXD[0]
TXD[1]/RXD[1]
1
0
0
1
Preamble
0
1
0
1
MSB
First Bit
LSB
1
0
Figure 3. 100 Mbps Transmission
D0
D1
First
Nibble
1
0
Figure 4. Bit Ordering
0
1
D0
Am79C875
1
0
D1
1
0
TXD[1:0] in 10 Mbps Mode
As the REF_CLK frequency is ten times the data rate
in 10 Mbps mode, the value on TXD[1:0] is valid such
that TXD[1:0] may be sampled every tenth cycle, re-
gardless of the starting cycle within the group and yield
the correct frame data.
Bit Ordering
Transmission and reception of each octet is done a di-
bit at a time with the order of di-bit transmission and
reception as shown in Figure 4.
scrambles the data, serializes it, and transmits an
MLT-3 data stream to the media via an isolation trans-
former. For 100BASE-FX applications, it encodes and
serializes the data and transmits a Pseudo-ECL
(PECL) data stream to the fiber optic transmitter.
The NetPHY™ 4LP transceiver receives an MLT-3
data stream from the network for 100BASE-TX. It then
recovers the clock from the data stream, de-serializes
the data stream, and descrambles/decodes the data
stream (5B/4B) before presenting it at the RMII inter-
face.
For 100BASE-FX operation, the NetPHY™ 4LP re-
ceives a PECL data stream from the fiber optic trans-
ceiver and decodes that data stream. 100BASE-FX
operation is possible only on Port 3.
MAC's Serial Bit Stream
0
1
D2
SFD
0
1
D3
1
1
D4
A
A
D5
B
B
D6
C
C
Data
D
D
D7
E
E
Second
Nibble
F
F
0
0
22236G-5
22236G-6
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