TLK3114SA_13 Datasheet, PDF (24/66 Pages) Texas Instruments – 10-Gbps XAUI Transceiver

RXxP
RXxN
RDx[7:0]
10-Bit Code Received
RLatency
Byte Received
RCLKx
Figure 3−6. Receiver Latency
3.10 Auto Detectable HSTL/SSTL_2 Class 1 I/O
The transmit and receive data buses of the TLK3114SA device are compatible with both high-speed transfer logic
(HSTL) supply and stub series terminated logic 2 (SSTL_2) Class 1 buffers. The TLK3114SA device determines
which buffer technology to use by sensing the voltage level on the V_DDQ supply terminals at power up. If the voltage
on the V_DDQ supply is between 2.3 V and 2.7 V, the TLK3114SA device provides the necessary drive current to meet
SSTL_2 Class 1 requirements. If the voltage on the V_DDQ supply is between 1.4 V and 2 V, the TLK3114SA device
provides HSTL compatible signaling. During normal operation, the voltage level on the V_DDQ terminals must not
change.
All HSTL/SSTL_2 Class 1 outputs are series terminated to provide direct connection to a 50-Ω transmission line
signaling environment (see Figure 4−10 and Figure 4−11).
3.11 8-b/10-b Encoder
All true serial interfaces require a method of encoding to ensure sufficient transition density for the receiving PLL to
acquire and maintain lock. The encoding scheme also maintains the signal dc balance by keeping the number of 1s
and 0s the same, which allows for ac-coupled data transmission. The TLK3114SA device uses the 8-b/10-b encoding
algorithm that is used by fibre channel and gigabit ethernet. This provides good transition density for clock recovery
and improves error checking. The 8-b/10-b encoder/decoder function is enabled for all four channels by the assertion
of the CODE terminal. When enabled, the TLK3114SA device internally encodes and decodes the data such that the
user reads and writes actual 8-bit data on each channel.
When enabled, the 8-b/10-b encoder converts 8-bit wide data to a 10-bit wide encoded data character to improve
its transition density. This transmission code includes D-characters, used for transmitting data, and K-characters,
used for transmitting protocol information. Each K- or D-character code word can also have both a positive and a
negative disparity version. The disparity of a code word is selected by the encoder to balance the running disparity
of the serialized data stream.
The generation of K-characters to be transmitted on each channel is controlled by TDx8 (KGEN). When KGEN is
asserted along with the 8 bits of data TDx[0:7], an 8-b/10-b K-character is transmitted. Similarly, reception of
K-characters is reported by RDx8 (KFLAG). When KFLAG is asserted, the 8 bits of data on RDx[0:7] must be
interpreted as a K-character. The TLK3114SA device transmits and receives all 12 valid K-characters defined in
Table 3−4. Table 3−5 provides additional transmit data control coding and descriptions that have been proposed for
10 gigabits per second ethernet. Data patterns put on TDx[0:7], other than those defined in Table 3−4 when TDx8
is asserted, result in an invalid K-character being transmitted, which results in a code error at the receiver.
3−5