Epic 3000
Programmer’s Guide
Programming Codes
100-14362
Rev A
Page 125
Aztec
The symbol is built on a square grid with a bulls-eye pattern at its centre for locating the
code. Data is encoded in concentric square rings around the bulls-eye pattern. The
central bulls-eye is 9×9 or 13×13 pixels, and one row of pixels around that encodes
basic coding parameters, producing a "core" of 11×11 or 15×15 squares. Data is added
in "layers", each one containing 2 rings of pixels, giving total sizes of 15×15, 19×19,
23×23, and so on.
The corners of the core include orientation marks, allowing the code to be read if rotated
or reflected. Decoding begins at the corner with three black pixels, and proceeds
clockwise to the corners with two, one and zero black pixels. The variable pixels in the
central core encode the size, so it is not necessary to mark the boundary of the code
with a blank "quiet zone", although some bar code readers require one.
The compact Aztec code core supports symbols from 15×15 (room for 13 digits or 12
letters) through 27×27. There is additionally a special 11×11 "rune" that encodes one
byte of information. The full core supports sizes up to 151x151, which can encode 3832
digits, 3067 letters, or 1914 bytes of data.
The level of Reed
–Solomon error correction is used for Aztec and the EPIC 3000 is
configurable, to 10%, 23%, 36% or 50% of the data region. The recommended level is
23%.
Aztec Code Standard is ISO/IEC 24778 (published February 2008)
All 8-bit values can be encoded. The default interpretation for values 1
12
–127 is ASCII
and for values 128
–255, ISO 8859-1
Figure 45
Aztec Symbol
Encoding: TransAct Technologies Inc. 20 Bomax Drive, Ithaca New York
12
The Aztec Standard allows values from 0 through 255. However, at this time the T480 will not
handle a NUL,
