CYP15G0403DX
PRELIMINARY
the patterns most similar to the encoded bit patterns of the Special
Character.
X3.230 Codes and Notation Conventions
Information to be transmitted over a serial link is encoded eight
bits at a time into a 10-bit Transmission Character and then
sent serially. Information received over a serial link is collected
ten bits at a time, and those Transmission Characters that are
used for data characters are decoded into the correct eight-bit
codes. The 10-bit Transmission Code supports all 256 8-bit
combinations. Some of the Special Transmission Characters
are used for other than data functions.
Under the above conventions, the Transmission Character
used for the examples above, is referred to by the name D5.2.
The Special Character K29.7 is so named because the first six
bits (abcdei) of this character make up a bit pattern similar to
that resulting from the encoding of the unencoded 11101
pattern (29), and because the second four bits (fghj) make up
a bit pattern similar to that resulting from the encoding of the
unencoded 111 pattern (7).
The primary use of a Transmission Code is to improve the
transmission characteristics of a serial link. The encoding
defined by the Transmission Code ensures that sufficient
transitions are present in the serial bit stream to recover the
clock at the Receiver. Such encoding increases the likelihood
of detecting bit errors that may occur. Some Special
Characters of the Transmission Code used by Fibre Channel
Standard consist of an easily recognizable bit pattern that
assists a Receiver in achieving word alignment.
Note. This definition of the 10-bit Transmission Code is based
on (and is in basic agreement with) the following references,
which describe the same 10-bit transmission code.
A.X. Widmer and P.A. Franaszek. “A DC-Balanced, Parti-
tioned-Block, 8B/10B Transmission Code” IBM Journal of
Research and Development, 27, No. 5: 440−451 (September,
1983).
U.S. Patent 4,486,739. Peter A. Franaszek and Albert X.
Widmer. “Byte-Oriented DC Balanced (0.4) 8B/10B Parti-
tioned Block Transmission Code” (December 4, 1984).
Notation Conventions
The documentation for the 8B/10B Transmission Code uses
letter notation for the bits in an 8-bit byte. Fibre Channel
Standard notation uses a bit notation of A, B, C, D, E, F, G, H
for the 8-bit byte for the raw 8-bit data, and the letters a, b, c,
d, e, i, f, g, h, j for encoded 10-bit data. There is a correspon-
dence between bit A and bit a, B and b, C and c, D and d, E
and e, F and f, G and g, and H and h. Bits i and j are derived,
respectively, from (A,B,C,D,E) and (F,G,H).
Fibre Channel Physical and Signaling Interface (ANS
X3.230−1994 ANSI FC−PH Standard).
IBM Enterprise Systems Architecture/390 ESCON I/O
Interface (document number SA22−7202).
8B/10B Transmission Code
The following information describes how the tables shall be
used for both generating valid Transmission Characters
(encoding) and checking the validity of received Transmission
Characters (decoding). It also specifies the ordering rules to
be followed when transmitting the bits within a character and
the characters within the higher-level constructs specified by
the standard.
The bit labeled A in the description of the 8B/10B Transmission
Code corresponds to bit 0 in the numbering scheme of the
FC-2 specification, B corresponds to bit 1, as shown below.
FC-2 bit designation—
HOTLink D/Q designation— 7
8B/10B bit designation—
7
6
6
G F
5
5
4
4
E
3
3
D
2
2
C
1
1
B
0
0
A
H
Transmission Order
To clarify this correspondence, the following example shows
the conversion from an FC-2 Valid Data Byte to a Transmission
Character (using 8B/10B Transmission Code notation).
Within the definition of the 8B/10B Transmission Code, the bit
positions of the Transmission Characters are labeled a, b, c,
d, e, i, f, g, h, j. Bit “a” shall be transmitted first followed by bits
b, c, d, e, i, f, g, h, and j in that order. (Note. Bit i shall be
transmitted between bit e and bit f, rather than in alphabetical
order.)
FC-2 45
Bits: 7654 3210
0100 0101
Converted to 8B/10B notation. (Note (carefully). The order of
bits is reversed.)
Valid and Invalid Transmission Characters
Data Byte Name
D5.2
Bits:ABCDEFGH
10100 010
The following tables define the valid Data Characters and valid
Special Characters (K characters), respectively. The tables
are used for both generating valid Transmission Characters
(encoding) and checking the validity of received Transmission
Characters (decoding). In the tables, each Valid-Data-byte or
Special-Character-code entry has two columns that represent
two (not necessarily different) Transmission Characters. The
two columns correspond to the current value of the running
disparity (“Current RD−” or “Current RD+”). Running disparity
is a binary parameter with either the value negative (−) or the
value positive (+).
Translated to a transmission Character in the 8B/10B Trans-
mission Code.
Bits: abcdeifghj
1010010101
Each valid Transmission Character of the 8B/10B Trans-
mission Code has been given a name using the following
convention: cxx.y, where c is used to show whether the Trans-
mission Character is a Data Character (c is set to D, and SC/D
= LOW) or a Special Character (c is set to K, and SC/D = HIGH).
When c is set to D, xx is the decimal value of the binary number
composed of the bits E, D, C, B, and A in that order, and the y is the
decimal value of the binary number composed of the bits H, G, and
F inthat order. Whenc is set to K, xx and y are derived by comparing
the encoded bit patterns of the Special Character to those patterns
derived from encoded Valid Data bytes and selecting the names of
After powering on, the Transmitter may assume either a
positive or negative value for its initial running disparity. Upon
transmission of any Transmission Character, the transmitter
will select the proper version of the Transmission Character
based on the current running disparity value, and the Trans-
mitter shall calculate a new value for its running disparity
based on the contents of the transmitted character. Special
Document #: 38-02033 Rev. *A
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