Advantech AMT-70, Installation And Operation Manual, Page: 117 / 160

AMT-70/AMT-73/AMT-75 Installation and Operation
The second axis is now encoded using
the appropriate component code Note
that the ECC bits generated by the first
encoding pass are in turn protected. This
results in an encoded block of 64 x 64 =
4096 bits.
The variety of available TPC codes is enormous: it is possible to use different component codes,
different coded block (array) sizes, to shorten the code by removing planes, rows, or individual bits,
and to apply an additional ‘enhanced’ coding pass. As a result, it is necessary to uniquely identify
the code. The convention for this is to describe each axis in terms of component code, uncoded and
coded block sizes.
So the code above can be uniquely described as:
eH (32, 26) eH (32,26) eH (16,11) – This is a 3D code with a 16384-bit block size, made up
of three extended Hamming codes.
And the following two compatible (Radyne / Comtech) codes are implemented
Rate ¾ - which is an exact 0.75 rate. It is a 4k bit block size and has no CRC
eH(64, 57)eH(64, 57)
Where each axis (X, then Y) is an extended Hamming (eH) component code encoding 57 bits to
produce 64 bits.
9.2
AMT7X family TPC Overview
The AMT-7x family of products supports the following codes:
eH (64, 57) eH (64, 57) P (4,3) – Another 3D/16384-bit code. In this case, the Z-axis code is
a parity-only code.
eH (64, 57) eH (64, 56) – This is a 2D 4096-bit code. It differs from the example because it
is shortened in the Y-axis to enable enhanced coding.
eH (128, 120) eH (128, 119) – A 2D enhanced code as the previous, however with the
larger 16384 bit block size.
eH (128, 120) P (128, 126) – Similar to the previous code, however using a parity-only code
in the Y-axis.
Rate 7/8 – an exact 0.875 rate. It is a 16k bit block size and has CRC.
9.2.1
CRCs and Scrambling
In all cases, a CRC is inserted into the uncoded data stream prior to encoding to determine the
presence of block errors after decode. The CRC word used is the CRC-32B algorithm. This
produces a 32-bit word that is inserted at the end of the uncoded data block.
117
Uncoded Data
ECC Bits
64 bits