S2046/S2050
GIGABIT ETHERNET CHIPSET
Loopback
S2046/S2050 OVERVIEW
Local loopback is supported by the chipset, and pro-
vides a capability for performing offline testing of the
interface to ensure the integrity of the serial channel
before enabling the transmission medium. It also al-
lows for system diagnostics.
The S2046 transmitter and S2050 receiver provide
serialization and deserialization functions for block-
encoded data to implement a Gigabit interface.
Operation of the S2046/S2050 chips is straightfor-
ward, as depicted in Figure 2. The sequence of
operations is as follows:
Figure 2. Interface Diagram
Transmitter
1. 10/20-bit parallel input
2. Parallel-to-serial conversion
3. Serial output
Parallel
Data Out
Parallel
Data In
Serial
Data
RCLK
TCLK
TX/Y
RX/Y
S2046
Transmitter
S2050
Receiver
Receiver
RCLKN
SYNC
TCLKN
1. Clock and data recovery from serial input
2. Serial-to-parallel conversion
3. Frame detection
Loopback
TLX/Y
RLX/Y
REFCLK
REFCLK
Loopback
4. 10/20-bit parallel output
The 10/20-bit parallel data handled by the S2046 and
S2050 devices should be from a DC-balanced en-
coding scheme, such as the 8B/10B transmission
code, in which information to be transmitted is en-
coded 8 bits at a time into 10-bit transmission
characters.
LOCKDETN
S2046 TRANSMITTER
Architecture/Functional Description
The S2046 transmitter accepts parallel input data and
serializes it for transmission over fiber optic or coaxial
cable media. The S2046 is fully compliant with the
proposed 802.3z Specification, and supports the Gi-
gabit Ethernet data rate of 1250 Mbps.
Internal clocking and control functions are transpar-
ent to the user. Details of data timing can be seen in
Figure 5.
A lock detect feature is provided on the receiver,
which indicates that the PLL is locked (synchronized)
to the data stream.
Figure 3. S2046 Functional Block Diagram
OE0
OE1
10
10
20
2:1
D
Q
D[19:0]
10
TX
TY
SHIFT
REGISTER
TEST
DWS
TLX
CONTROL
LOGIC
TLY
REFSEL
REFCLK
TCLK
DIVIDE-BY-2
PLL CLOCK
MULTIPLIER
TCLKN
F = F X 10/20
0
1
March 29, 2000 / Revision B
2
AMCC [ APPLIED MICRO CIRCUITS CORPORATION ]
