high speed serial transmission of data over fiber op-
tic, coax, or twinax interfaces. The device conforms
to the requirements of the IEEE 802.3z Gigabit
Ethernet specification, and runs at 1250.0 Mbps data
rates with an associated 10-bit data word.
allel conversion, clock generation/recovery, and
framing for block encoded data. The on-chip transmit
PLL synthesizes the high-speed clock from a low-
speed reference. The on-chip receive PLL performs
clock recovery and data re-timing on the serial bit
stream. The transmitter and receiver each support
differential LVPECL compatible I/O for copper or fi-
ber optic component interfaces with excellent signal
integrity. Local loopback mode allows for system di-
agnostics. The chip requires a +3.3 V power supply
and dissipates typically 620 mW.
including Gigabit Ethernet, serial backplanes, and
proprietary point-to-point links. Figure 1 shows a
typical configuration incorporating the chip.
ization and deserialization functions for block en-
coded data to implement a Gigabit Ethernet
interface. The S2060 functional block diagram is de-
picted in Figure 2. The sequence of operations is as
2. Parallel-to-serial conversion
3. Serial output
2. Serial-to-parallel conversion
3. Frame detection
4. 10-bit parallel output
from a DC-balanced encoding scheme, such as the
8B/10B transmission code, in which information to be
transmitted is encoded 8 bits at a time into 10-bit trans-
off-line testing. This is useful for ensuring the integ-
rity of the serial channel before enabling the trans-
mission medium. It also allows for system
anced (0,4) 8B/10B Transmission Code," IBM Research Report
RC 9391, May 1982.
data and serializes it for transmission over fiber optic
or coaxial cable media. The chip is fully compatible
with the IEEE 802.3z Gigabit Ethernet standard, and
supports the Gigabit Ethernet data rate of 1250.0
Mbps. The S2060 uses a PLL to generate the serial
rate transmit clock. The transmitter runs at 10 times
the TBC input clock, and operates in either full rate
or half rate mode. At the full VCO rate the transmitter
runs at 1.25 GHz, while in half rate mode it operates
at 625 MHz.
data from the input latch and converts it to a serial
data stream. Parallel data is latched into the trans-
mitter on the positive going edge of TBC. The data is
then clocked into the serial output shift register. The
shift register is clocked by the internally generated
bit clock which is 10x the TBC input frequency. TX
is transmitted first.
plied from a clock source with 100 ppm tolerance to
assure that the transmitted data meets the Gigabit
Ethernet frequency limits. The internal serial clock is
frequency locked to TBC (125.00 MHz).
the state of the RATEN input. Operating rates are
shown in Table 2.
to recover the serial clock from the received data
stream. The S2060 searches the serial bit stream for
the occurrence of a positive polarity COMMA sync
pattern (0011111xxx positive running disparity) to
perform word synchronization. Once synchronization
on both bit and word boundaries is achieved, the
receiver provides the decoded data on its parallel
stream. A simple state machine in the clock recovery
macro decides whether to acquire lock from the se-
rial data input or from the reference clock. The deci-
sion is based upon the frequency and run length of
the input serial data.
the S2060 will respond to variations in the serial data
input frequency (as compared to the reference fre-
quency). The new lock state is dependent upon the
current lock state, as shown in Table 3. The run-
length criteria ensure that the S2060 will respond ap-
length checker flags a condition of consecutive ones
or zeros across 12 parallel words. Thus, 119 or less
consecutive ones or zeros does not cause signal loss,
129 or more causes signal loss, and 120 128 may
or may not, depending on how the data aligns across
byte boundaries. If both the off-frequency detect test
and the run-length test is satisfied, the CRU will at-
tempt to lock to the incoming data.
data and the reference clock, the RBC0 and RBC1
remain phase continuous and glitch free, assuring
the integrity of downstream clocking.
jitter clock source. The frequency of the received
data stream must be within 400 ppm of the reference
clock to ensure reliable locking of the receiver PLL.
A single reference clock is provided to both the
transmit and receive PLL's.
allel output data, determined by the state of
EN_CDET. With EN_CDET held ACTIVE, the S2060
will detect and align to the 8B/10B COMMA
codeword anywhere in the data stream. When
EN_CDET is INACTIVE, no attempt is made to syn-
chronize on any particular incoming character. The
S2060 will achieve bit synchronization within 250 bit
times and begin to deliver unframed parallel output
data words whenever it has received full transmis-
sion words. Upon change of state of the EN_CDET
input, the COM_DET output response will be de-
layed by a maximum of 3 byte times.
EN_CDET is active and the COMMA control charac-
ter is present on the RX[0:9] parallel data outputs.
The COM_DET output signal will be INACTIVE at all
puts, selected via the RATEN input. Table 4 shows
the operating rate scenarios. When RATEN is INAC-
TIVE, a data clock is provided on RBC1 at the data
rate. Data should be clocked on the rising edge of
RBC1. When RATEN is ACTIVE the device is in full
rate mode, and complementary TTL clocks are pro-
vided on the RBC0 and RBC1 outputs at 1/2 the
data rate as required by the Gigabit Ethernet Stan-
dard. Data is clocked on the rising edges of both
RBC0 and RBC1. See Figures 11 and 12.
quire that the COMMA sync character appears on
the rising edge of the RBC1 signal. In full rate mode
the phase of the data is adjusted such that this re-
quirement is met. No alignment is necessary when
the S2060 is operating in half rate mode since the
output clock frequency is equal to the parallel word
rate (RATEN INACTIVE).
secutive COMMA characters to be generated. How-
ever, multiple consecutive COMMA characters can
occur in serial backplane applications. The S2060 is
able to operate properly when multiple consecutive
COMMA characters are received: after the first
COMMA is detected and aligned, the RBC0/RBC1
clock operates without glitches or loss of cycles.
Additionally, COM_DET stays high while multiple
COMMAS are being output.