GS1 EPC Tag Data Standard 1.6 - Indicod-Ecr

4624462546264627462846294630463146324633463446354636463746384639464046414642464346444645464646474648464946504651465246534654465546564657465846594660466146624663466446654666needs to be represented by a pair of base-30 values, and thus each such data character isrepresented by a pair of ‘1’ bits in the character map.I.8.2.3 Prefix and Suffix Run-Length encodingFor improved efficiency in cases where the concatenated sequence includes runs of six ormore values from the same base, provision is made for optional run-lengthrepresentations of one or more Prefix or Suffix “Runs” (single-base character sequences),which can replace the first and/or last portions of the character map. The encoder shallnot create a Run that separates a Shift value from its next (shifted) value, and thus a Runalways represents an integral number of source characters.An optional Prefix Representation, if present, consists of one or more occurrences of aPrefix Run. Each Prefix Run consists of one Run Position bit, followed by two BasisBits, then followed by three Run Length bits, defined as follows: The Run Position bit, if ‘0’, indicates that at least one more Prefix Run is encodedfollowing this one (representing another set of source characters to the right of thecurrent set). The Run Position bit, if ‘1’, indicates that the current Prefix Run is thelast (rightmost) Prefix Run of the A/N subsection. The first basis bit indicates a choice of numeric vs. non-numeric base, and the secondbasis bit, if ‘1’, indicates that the chosen base is extended to include characters fromthe “opposite” base. Thus, ‘00’ indicates a run-length-encoded sequence of base 10values; ‘01’ indicates a sequence that is primarily (but not entirely) digits, encoded inBase 13; ‘10’ indicates a sequence a sequence of values from the non-numeric basethat was selected earlier in the A/N header, and ‘11’ indicates a sequence of valuesprimarily from that non-numeric base, but extended to include digit characters aswell. Note an exception: if the non-numeric base that was selected in the A/N headeris Base 256, then the “extended” version is defined to be Base 40. The 3-bit Run Length value assumes a minimum useable run of six same-basecharacters, and the length value is further divided by 2. Thus, the possible 3-bit RunLength values of 0, 1, 2, … 7 indicate a Run of 6, 8, 10, … 20 characters from thesame base. Note that a trailing “odd” character value at the end of a same-basesequence must be represented by adding a bit to the Character Map.An optional Suffix Representation, if present, is a series of one or more Suffix Runs, eachidentical in format to the Prefix Run just described. Consistent with that description, notethat the Run Position bit, if ‘1’, indicates that the current Suffix Run is the last(rightmost) Suffix Run of the A/N subsection, and thus any preceding Suffix Runsrepresented source characters to the left of this final Suffix Run.I.8.2.4 Encoding into Binary SegmentsImmediately after the last bit of the Character Map, up to four binary numbers areencoded, each representing all of the characters that were encoded in a single basesystem. First, a base-13 bit sequence is encoded (if one or more Prefix or Suffix Runscalled for base-13 encoding). If present, this bit sequence directly represents the binarynumber resulting from encoding the combined sequence of all Prefix and Suffixcharacters (in that order) classified as Base 13 (ignoring any intervening characters notthus classified) as a single value, or in other words, applying a base 13 to BinaryCopyright ©2005- 2011 GS1 AISBL, All Rights Reserved. Page 183 of 218