TLK3118 Datasheet, PDF (8/57 Pages) Texas Instruments – Redundant XAUI Transceiver

TLK3118
Redundant XAUI Transceiver
SLLS628A – DECEMBER 2004 – REVISED APRIL 2005
www.ti.com
Detailed Description (continued)
8B/10B Encoder
All true serial interfaces require a method of encoding to insure 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 ones and zeros are balanced which allows for AC coupled data transmission. The TLK3118 uses the 8B/10B
encoding algorithm that is used by 10Gbps and 1Gbps Ethernet and Fiber Channel standards. This provides
good transition density for clock recovery and improves error checking. The 8B/10B encoder/decoder function is
enabled for all serial links. The TLK3118 will internally encode and decode the data such that the user reads and
writes actual 8-bit data on each channel.
The 8B/10B 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 transmit control pins,
TXC(3:0). When the control pin is asserted along with the 8 bits of data, an 8B/10B K-character is transmitted.
Similarly, reception of K-characters is reported by the receive control pins, RXC(3:0). When receive control pin is
asserted, the corresponding byte on the receive data bus should be interpreted as a K-character. The TLK3118
will transmit and receive all of the twelve valid K-characters as defined below.
K-Code
00 through FF
K28.0
K28.1
K28.2
K28.3
K28.4
K28.5
K28.6
K28.7
K23.7
K27.7
K29.7
K30.7
TXC(3:0) or
RXC(3:0)
0
1
1
1
1
1
1
1
1
1
1
1
1
Table 1. Valid K-Codes
Data Bus Bytes
(RXD[x: x-7] or
TXD[x: x-7])
DDD DDDDD
000 11100
001 11100
010 11100
011 11100
100 11100
101 11100
110 11100
111 11100
111 10111
111 11011
111 11101
111 11110
Encoded K-code
Negative Run-
ning Disparity
Positive Run-
ning Disparity
dddddd dddd
dddddd dddd
001111 0100
110000 1011
001111 1001
110000 0110
001111 0101
110000 1010
001111 0011
110000 1100
001111 0010
110000 1101
001111 1010
110000 0101
001111 0110
110000 1001
001111 1000
110000 0111
111010 1000
000101 0111
110110 1000
001001 0111
101110 1000
010001 0111
011110 1000
100001 0111
K-Code Description
Normal data
IdleO/busy
IdleE/busy
Channel Alignment Pre-Cursor
IdleE/not-busy
Code Violation or Parity Error
IdleO/not-busy
SOP(S)
EOP(T)
Table 2 provides additional transmit data control coding and descriptions that have been incorporated into 10
Gigabits per second Ethernet. Data patterns put on XGMII transmit data bus other than those defined in Table 2
when the transmit control pin is asserted will result in an invalid K-character being transmitted which will result in
a code error at the receiver.
Table 2. Valid XGMII Channel Encodings
Data Bus (TXD[x: x-7] or TXC(3:0) or RXC(3:0)
RXD[x: x-7])
00 through FF
0
00 through 06
1
07
1
08 through 9B
1
9C
1
9D through FA
1
Description
Normal Data Transmission
Reserved
Idle
Reserved
Sequence (only valid in Channel A)
Reserved
8