ISO/IEC 15438:2001

Information technology - Automatic identification and data capture techniques - Bar code symbology specifications - PDF417

Technologies de l'information — Techniques automatiques d'identification et de capture des données — Spécifications pour les symboles de codes à barres — PDF417

General Information

• Status: Withdrawn
• Publication Date: 10-Oct-2001
• Withdrawal Date: 10-Oct-2001
• ICS: 35.040 - Information coding
• ICS: 35.040.50 - Automatic identification and data capture techniques
• Technical Committee: ISO/IEC JTC 1/SC 31 - Automatic identification and data capture techniques
• Drafting Committee: ISO/IEC JTC 1/SC 31 - Automatic identification and data capture techniques
• Current Stage: 9599 - Withdrawal of International Standard
• Start Date: 24-May-2006
• Completion Date: 30-Oct-2025

Relations

• Revised: ISO/IEC 15438:2006 - Information technology - Automatic identification and data capture techniques - PDF417 bar code symbology specification
• Effective Date: 15-Apr-2008

Standards Content (Sample)

INTERNATIONAL ISO/IEC
STANDARD 15438
First edition
2001-09-15
Information technology — Automatic
identification and data capture
techniques — Bar code symbology
specifications — PDF417
Technologies de l'information — Techniques automatiques d'identification
et de capture des données — Spécifications pour les symboles de codes à
barres — PDF417
Reference number
©
ISO/IEC 2001
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ii © ISO/IEC 2001 – All rights reserved

Contents Page
Foreword.vi
Introduction.vii
1 Scope .1
2 Normative references.1
3 Definitions, mathematical symbols and abbreviations .2
3.1 Terms and definitions .2
3.1.1 Basic Channel Model: .2
3.1.2 Bar-space sequence:.2
3.1.3 Cluster: .2
3.1.4 Compaction mode: .2
3.1.5 Error correction codeword: .2
3.1.6 Extended Channel Interpretation:.3
3.1.7 Extended Channel Model:.3
3.1.8 Function codeword: .3
3.1.9 Global Label Identifier:.3
3.1.10 Macro PDF417:.3
3.1.11 Mode Latch codeword:.3
3.1.12 Mode Shift codeword: .3
3.1.13 Row Indicator codeword:.3
3.1.14 Symbol Length Descriptor:.4
3.2 Mathematical symbols and operations .4
3.3 Abbreviations.5
4 Requirements.5
4.1 Symbology characteristics.5
4.1.1 Basic characteristics.5
4.1.2 Summary of additional features.6
4.2 Symbol structure .7
4.2.1 PDF417 symbol parameters .7
4.2.2 Row parameters.7
4.2.3 Codeword sequence.8
4.3 Basic encodation .9
4.3.1 Symbol character structure.9
4.3.2 Start and stop characters .9
4.4 High level (data) encodation.10
4.4.1 Function codewords.11
4.4.2 Text Compaction mode.13
4.4.3 Byte Compaction mode.19
4.4.4 Numeric Compaction mode.20
4.4.5 Advice to select the appropriate compaction mode .22
4.4.6 Treatment of PDF417 reserved codewords.22
4.5 Extended Channel Interpretation .23
4.5.1 Encoding the ECI assignment number.23
4.5.2 Pre-assigned Extended Channel Interpretations .24
4.5.3 Encoding ECI sequences within compaction modes .25
4.5.4 Post-decode protocol.27
4.6 Determining the codeword sequence.27
4.7 Error detection and correction.27
4.7.1 Error correction level .27
4.7.2 Error correction capacity.28
4.7.3 Defining the error correction codewords.29
© ISO/IEC 2001 – All rights reserved iii

4.8 Dimensions.29
4.8.1 Minimum width of a module (X).29
4.8.2 Row height (Y).29
4.8.3 Quiet zones.29
4.9 Defining the symbol format .29
4.9.1 Defining the aspect ratio of the module .30
4.9.2 Defining the symbol matrix of rows and columns .30
4.10 Generating the error correction codewords .31
4.11 Low level encodation .33
4.11.1 Clusters.34
4.11.2 Determining the symbol matrix .34
4.11.3 Determining the values of the left and right row indicators.34
4.11.4 Row encoding .35
4.12 Compact PDF417 .35
4.13 Macro PDF417 .35
4.13.1 Compaction modes and Macro PDF417 .35
4.13.2 ECIs and Macro PDF417.35
4.14 User guidelines .36
4.14.1 Human readable interpretation.36
4.14.2 Autodiscrimination capability .36
4.14.3 User-defined application parameters .36
4.14.4 PDF417 symbol quality .37
4.15 Reference decode algorithm .37
4.16 Error detection and error correction procedure.37
4.17 Transmitted data.37
4.17.1 Transmitted data in the basic (default) interpretation .37
4.17.2 Transmission protocol for Extended Channel Interpretation (ECI).37
4.17.3 Transmitted data for Macro PDF417 .38
4.17.4 Transmission of reserved codewords using the ECI protocol .39
4.17.5 Symbology identifier .39
4.17.6 Transmission using older protocols.39
Annex A (normative) Encoding/decoding table of PDF417 symbol character bar-space sequences .40
Annex B (normative) The default character set for Byte Compaction mode.55
Annex C (normative) Byte Compaction mode encoding algorithm .56
Annex D (normative) Numeric Compaction mode encoding algorithm .58
Annex E (normative) User selection of error correction.60
Annex F (normative) Tables of coefficients for calculating PDF417 error correction codewords .61
Annex G (normative) Compact PDF417 .66
Annex H (normative) Macro PDF417 .67
Annex J (normative) Testing PDF417 symbol quality .75
Annex K (normative) Reference decode algorithm for PDF417 .77
Annex L (normative) Error correction procedures .81
Annex M (normative) Symbology identifier.83
Annex N (normative) Transmission protocol for decoders conforming with earlier PDF417 standards .84
Annex P (informative) Algorithm to minimise the number of codewords.90
Annex Q (informative) Guidelines to determine the symbol matrix.91
Annex R (informative) Calculating the coefficients for generating the error correction codewords –
worked example .95
Annex S (informative) Generating the error correction codewords — worked example.96
Annex T (informative) Division circuit procedure for generating error correction codewords .100
iv © ISO/IEC 2001 – All rights reserved

Annex U (informative) Autodiscrimination compatibility.101
Bibliography.102

© ISO/IEC 2001 – All rights reserved v

Foreword
ISO (the International Organization for Standardization) and IEC (the International Electrotechnical Commission)
form the specialized system for worldwide standardization. National bodies that are members of ISO or IEC
participate in the development of International Standards through technical committees established by the
respective organization to deal with particular fields of technical activity. ISO and IEC technical committees
collaborate in fields of mutual interest. Other international organizations, governmental and non-governmental, in
liaison with ISO and IEC, also take part in the work. In the field of information technology, ISO and IEC have
established a joint technical committee, ISO/IEC JTC 1.
International Standards are drafted in accordance with the rules given in the ISO/IEC Directives, Part 3.
The main task of the joint technical committee is to prepare International Standards. Draft International Standards
adopted by the joint technical committee are circulated to national bodies for voting. Publication as an International
Standard requires approval by at least 75 % of the national bodies casting a vote.
Attention is drawn to the possibility that some of the elements of this International Standard may be the subject of
patent rights. ISO and IEC shall not be held responsible for identifying any or all such patent rights.
ISO/IEC 15438 was prepared by Joint Technical Committee ISO/IEC JTC 1, Information technology, Subcommittee
SC 31, Automatic identification and data capture techniques.
Annexes A to N form a normative part of this International Standard. Annexes P to U are for information only.
vi © ISO/IEC 2001 – All rights reserved

Introduction
The technology of bar coding is based on the recognition of patterns of bars and spaces of defined dimensions.
There are various methods of encoding information in bar code form, known as symbologies, and the rules defining
the translation of characters into bar and space patterns and other essential features are known as the symbology
specification.
Manufacturers of bar code equipment and users of bar code technology require publicly available standard
symbology specifications to which they can refer when developing equipment and application standards. It is the
intent and understanding of ISO/IEC that the symbology presented in this standard is entirely in the public domain
and free of all user restrictions, licences and fees.
© ISO/IEC 2001 – All rights reserved vii

INTERNATIONAL STANDARD ISO/IEC 15438:2001(E)

Information technology — Automatic identification and data
capture techniques — Bar code symbology specifications —
PDF417
1 Scope
This International Standard specifies the requirements for the bar code symbology known as PDF417. It specifies
PDF417 symbology characteristics, data character encodation, symbol formats, dimensions, error correction rules,
decoding algorithm, and a number of application parameters.
2 Normative references
The following normative documents contain provisions which, through reference in this text, constitute provisions of
this International Standard. For dated references, subsequent amendments to, or revisions of, any of these
publications do not apply. However, parties to agreements based on this International Standard are encouraged to
investigate the possibility of applying the most recent editions of the normative documents indicated below. For
undated references, the latest edition of the normative document referred to applies. Members of ISO and IEC
maintain registers of currently valid International Standards.
ISO/IEC 646:1991, Information technology — ISO 7-bit coded character set for information exchange
ISO/IEC 8859-1:1998, Information technology — 8-bit single-byte coded graphic character sets — Part 1: Latin
alphabet No. 1
ISO/IEC 15416, Information technology — Automatic identification and data capture techniques — Bar code print
quality test specification — Linear Symbols
AIM International Technical Specification: Extended Channel Interpretations — Part 1: Identification Schemes and
Protocol
AIM International Technical Specification: Extended Channel Interpretations — Part 2: Registration of Coded
Character Sets and Other Data Formats
EN 796, Bar coding — Symbology identifiers
EN 1556, Bar coding — Terminology
© ISO/IEC 2001 – All rights reserved 1

3 Definitions, mathematical symbols and abbreviations
3.1 Terms and definitions
For the purposes of this International Standard, the following terms and definitions given in EN 1556 apply.
algorithm, application standard, ASCII, autodiscrimination, bar, bar code, bi-directional, binary, bit, codeword,
column, continuous code, data character, data codeword, data compaction, data region, decode algorithm,
decoder, element, encode, error correction level, human readable character, leading zeros, linear symbology,
module, modulo, multi-row symbology, n, k symbology, numeric, overhead, pad character, pad codeword, quiet
zone, reference decode algorithm, row, scanner, self-checking, space, start character, stop character, symbol
aspect ratio, symbol character, symbology, symbology identifier, symbol width, X-dimension, Y-dimension
The following definitions also apply to this International Standard.

3.1.1 Basic Channel Model:
A standard system for encoding and transmitting bar code data where data message bytes are output from the
decoder but no control information about the message is transmitted. A decoder, complying to this model,
operates in Basic Channel Mode.

3.1.2 Bar-space sequence:
The sequence which represents the module widths of the elements of a symbol character.

3.1.3 Cluster:
One of three subsets of PDF417 symbol characters, all of which are mutually exclusive. The symbol characters in
a given cluster conform with particular structural rules which are used in decoding the symbology.

3.1.4 Compaction mode:
The name given to one of three data compaction algorithms in PDF417: Text, Numeric and Byte Compaction
modes. These modes efficiently map 8-bit data bytes into PDF417 codewords.

3.1.5 Error correction codeword:
A codeword in a symbol which encodes a value derived from the error correction codeword algorithm to enable
decode errors to be detected and, depending on the error correction level, to be corrected.
2 © ISO/IEC 2001 – All rights reserved

3.1.6 Extended Channel Interpretation:
A procedure within some symbologies, including PDF417, to replace the default interpretation with another
interpretation in a reliable manner. The interpretation intended prior to producing the symbol can be retrieved after
decoding the scanned symbol to recreate the data message in its original format.

3.1.7 Extended Channel Model:
A system for encoding and transmitting both data message bytes and control information about the message. A
decoder, complying to this model, operates in Extended Channel Mode. The control information is communicated
using Extended Channel Interpretation (ECI) escape sequences.

3.1.8 Function codeword:
A codeword in a symbology which initiates a particular operation within the symbology, for example to switch
between data encoding sets, to invoke a compaction scheme, to program the reader, to invoke Extended Channel
Interpretations.
3.1.9 Global Label Identifier:
A procedure in the PDF417 symbology, which behaves in a similar manner to Extended Channel Interpretation.
The GLI system was the symbology-dependent precursor to the symbology-independent ECI system.

3.1.10 Macro PDF417:
A procedure within the PDF417 symbology to logically distribute data from a computer file across a number of
related PDF417 symbols. The procedure considerably extends the data capacity beyond that of a single symbol.
This procedure is similar to the Structured Append feature in other symbologies.

3.1.11 Mode Latch codeword:
A codeword which is used to switch from one mode to another mode, which stays in effect until another latch or
shift codeword is implicitly or explicitly brought into use, or until the end of the label is reached.

3.1.12 Mode Shift codeword:
A codeword which is used to switch from one mode to another for one codeword, after which encoding returns to
the original mode.
3.1.13 Row Indicator codeword:
A PDF417 codeword adjacent to the start or stop character in a row, which encodes information about the structure
of the PDF417 symbol in terms of the row identification, total number of rows and columns, and the error correction
level.
© ISO/IEC 2001 – All rights reserved 3

3.1.14 Symbol Length Descriptor:
The codeword in a PDF417 symbol which encodes the total number of data codewords in the symbol. The Symbol
Length Descriptor shall always be the first codeword in a PDF417 symbol.
3.2 Mathematical symbols and operations
For the purposes of this standard the mathematical symbols which follow shall apply. There are some cases where
the symbols below have been used in a different manner in an equation. This has been done for consistency with
a more general use of the notation and is always clearly defined in the text.
A symbol aspect ratio (height to width) of a PDF417 symbol
b the element width in a symbol character
c number of columns in the symbol in the data region (excluding start, stop and row indicator codewords)
d data codeword including all function codewords
E error correction codeword
e an edge to similar edge dimension in a symbol character
F row number
f number of substitution errors
H height of symbol including quiet zone
K cluster number
k number of error correction codewords
L left row indicator
l number of erasures
m number of source data codewords prior to the addition of the Symbol Length Descriptor and any pad
codewords
n total number of data codewords including Symbol Length Descriptor and any pad codewords
p the pitch or width of a symbol character
Q horizontal quiet zone
H
Q vertical quiet zone
V
R right row indicator
r number of rows in the symbol
s error correction level
W width of symbol including quiet zone
X X-dimension or module width
Y module height (also called row height)

4 © ISO/IEC 2001 – All rights reserved

For the purposes of this standard the mathematical operations which follow shall apply:
div is the integer division operator, rounding down
INT is the integer value i.e. where a number is rounded down to its whole number component, ignoring its
decimal fractions
mod is the positive integer remainder after division. If the remainder is negative, add the value of the divisor
to make it positive. For example, the remainder of -29 160 divided by 929 is -361 which when added to
929 yields 568.
3.3 Abbreviations
For the purposes of this standard, the following abbreviations shall apply:
ECI Extended Channel Interpretation
GLI Global Label Identifier
4 Requirements
4.1 Symbology characteristics
4.1.1 Basic characteristics
PDF417 is a bar code symbology with the following basic characteristics:
a. Encodable character set:
1. Text Compaction mode (see 4.4.2) permits all printable ASCII characters to be encoded, i.e.
values 32 - 126 inclusive in accordance with ISO/IEC 646, as well as selected control characters.
2. Byte Compaction mode (see 4.4.3) permits all 256 possible 8-bit byte values to be encoded. This
includes all ASCII characters value 0 to 127 inclusive and provides for international character set
support.
3. Numeric Compaction mode (see 4.4.4) permits efficient encoding of numeric data strings.
4. Up to 811 800 different character sets or data interpretations.
5. Various function codewords for control purposes.
b. Symbol character structure: (n, k, m) characters of 17 modules (n), 4 bar and 4 space elements (k), with
the largest element 6 modules wide (m).
c. Maximum possible number of data characters per symbol (at error correction level 0): 925 data codewords
which can encode:
1. Text Compaction mode: 1 850 characters (at 2 data characters per codeword).
2. Byte Compaction mode: 1 108 characters (at 1,2 data characters per codeword).
3. Numeric Compaction mode: 2 710 characters (at 2,93 data characters per codeword)
At the minimum recommended error correction level, there are 863 data codewords which can encode:
© ISO/IEC 2001 – All rights reserved 5

1. Text Compaction mode: 1 726 characters (at 2 data characters per codeword).
2. Byte Compaction mode: 1 033 characters (at 1,2 data characters per codeword).
3. Numeric Compaction mode: 2 528 characters (at 2,93 data characters per codeword)
d. Symbol size:
1. Number of rows: 3 to 90.
2. Number of columns: 1 to 30.
3. Width in modules: 90X to 583X including quiet zones.
4. Maximum codeword capacity: 928 codewords.
5. Maximum data codeword capacity: 925 codewords.
Since the number of rows and the number of columns are selectable, the aspect ratio of a PDF417 symbol
may be varied when printing to suit the spatial requirements of the application.
e. Selectable error correction: 2 to 512 codewords per symbol (see 4.7).
f. Non-data overhead:
1. Per row: 73 modules, including quiet zones.
2. Per symbol: a minimum of 3 additional codewords, represented as symbol characters.
g. Code type: continuous, multi-row two-dimensional.
h. Character self-checking: Yes.
i. Bi-directionally decodable: Yes.

4.1.2 Summary of additional features
The following summary is of additional features which are inherent or optional in PDF417:
a. Data compaction: (inherent) Three schemes are defined to compact a number of data characters into
codewords. Generally data is not directly represented on a one character for one codeword basis (see
4.4.2 to 4.4.4).
b. Extended Channel Interpretations: (optional) These mechanisms allow up to 811 800 different data
character sets or interpretations to be encoded (see 4.5).
c. Macro PDF417: (optional) This mechanism allows files of data to be represented logically and
consecutively in a number of PDF417 symbols. Up to 99 999 different PDF417 symbols can be so linked
or concatenated and be scanned in any sequence to enable the original data file to be correctly
reconstructed (see 4.13).
d. Edge to edge decodable: (inherent) PDF417 can be decoded by measuring elements from edge to similar
edge (see 4.3.1).
e. Cross row scanning: (inherent) The combination of the following three characteristics in PDF417
facilitates cross row scanning:
• being synchronised horizontally, or self clocking
• row identification
• being vertically synchronised, by using the cluster values to achieve local row discrimination.
6 © ISO/IEC 2001 – All rights reserved

This combination allows a single linear scan to cross a number of rows and achieve a partial decode of the
data so long as at least one complete symbol character per row is decoded into its codeword. The
decoding algorithm can then place the individual codewords into a meaningful matrix.
f. Error correction: (inherent) A user may define one of 9 error correction levels. All but Level 0 not only
detect errors but can correct erroneously decoded or missing codewords (see 4.7).
g. Compact PDF417: (optional) In relatively ‘clean' environments, it is possible to reduce some of the row
overhead to improve the symbol density (see 4.12).
NOTE: In earlier specifications of PDF417, this was called Truncated PDF417. Compact PDF417 is the preferred term to avoid
confusion with the more general use of the term ‘truncated'.
4.2 Symbol structure
4.2.1 PDF417 symbol parameters
Each PDF417 symbol consists of a stack of vertically aligned rows with a minimum of 3 rows (maximum 90 rows).
Each row shall include a minimum of 1 symbol character (maximum 30 symbol characters), excluding start, stop
and row indicator columns. The symbol shall include a quiet zone on all four sides. Figure 1 illustrates a PDF417
symbol encoding the text: PDF417 Symbology Standard.

Figure 1 — PDF417 Symbol Structure
4.2.2 Row parameters
Each PDF417 row shall comprise:
a. leading quiet zone
b. start character
c. left row indicator symbol character
d. 1 to 30 symbol characters
e. right row indicator symbol character
f. stop character
g. trailing quiet zone
NOTE: The number of symbol characters (or codewords) defined in item ‘d' above is equal to the number of data columns in the
PDF417 symbol.
© ISO/IEC 2001 – All rights reserved 7

4.2.3 Codeword sequence
A PDF417 symbol may contain up to 928 symbol characters or codewords. Symbol character is the more
appropriate term to refer to the printed bar/space pattern; codeword is more appropriate for the numeric value of
the symbol character. The codewords shall follow this sequence:
a. The first codeword, the Symbol Length Descriptor, shall always encode the total number of data
codewords in the symbol, including the Symbol Length Descriptor itself, data codewords and pad
codewords, but excluding the number of error correction codewords.
b. The data codewords shall follow; from the most significant encodable character. Function codewords may
be inserted to achieve data compaction.
c. Pad codewords to enable the codeword sequence to be represented in a rectangular matrix. Pad
codewords may also be used to fill additional complete rows to achieve an aspect ratio desired or as
specified by the application.
d. An optional Macro PDF417 Control Block.
e. Error correction codewords for error detection and correction.
The codewords are arranged with the most significant codeword adjacent to the Symbol Length Descriptor, and are
encoded from left to right top row to bottom. Figure 2 illustrates in layout format the sequence for the symbol like
that shown in Figure 1. In Figure 2 an error correction level of 1 has been used and one pad character was needed
to completely fill the symbol matrix.

L d d R
1 15 14 1
L d d R
2 13 12 2
S L d d R S
3 11 10 3
T L d d R T
4 9 8 4
A L d d R O
5 7 6 5
R L d d R P
6 5 4 6
T L d d R
7 3 2 7
L d d R
8 1 0 8
L E E R
9 3 2 9
L E E R
10 1 0 10
Figure 2 — PDF417 Example of Symbol Layout Schematic

where L, R, d and E are as defined in 3.2
d  = Symbol Length Descriptor (in this example, with a value of 16)
d to d = encoded representation of data
14 1
d  = pad codeword
The rules and advice for structuring the matrix are included in 4.9.
8 © ISO/IEC 2001 – All rights reserved

4.3 Basic encodation
4.3.1 Symbol character structure
Each PDF417 symbol character shall consist of four bar elements and four space elements, each of which can be
one to six modules wide. The four bar and four space elements shall measure 17 modules in total.  PDF417
symbol characters can be decoded by measuring the e-distances within the character.
Each symbol character is defined by an 8-digit bar-space sequence which represents the module widths of the
eight elements of that symbol character. Figure 3 illustrates a symbol character with the bar-space sequence
51111125.
Figure 3 — A PDF417 Symbol Character
There are 929 defined symbol character values (codewords) numbered from 0 to 928.
The codewords are represented by three mutually exclusive symbol character sets, or clusters. Each cluster
encodes the 929 available PDF417 codewords into different bar-space patterns so that one cluster is distinct from
another. The cluster numbers are 0, 3, 6. The cluster definition applies to all PDF417 symbol characters, except
for start and stop characters.
The cluster number K is defined by the following formula:
K = (b - b + b - b + 9) mod 9
1 2 3 4
Where b , b , b and b represent the width in modules of the four bar elements respectively
1 2 3 4
The cluster number K for the symbol character in Figure 3 is:
K = (5 - 1 + 1 - 2 + 9) mod 9 = 3
The codewords and the bar-space sequences for each cluster of symbol characters are given in Annex A.
4.3.2 Start and stop characters
The start and stop characters shall be composed as defined in Table 1 and illustrated in Figure 4:

© ISO/IEC 2001 – All rights reserved 9

Table 1 — Bar-space sequence for Start and Stop Characters
Character Bar-space  sequence
B S B S B S B S B
Start 8 1 1 1 1 1 1 3
Stop 7 1 1 3 1 1 1 2 1
NOTE 1: The PDF417 stop and start characters are unique in having elements more than 6 modules wide.
NOTE 2: The stop character has one extra single module bar element.
The start and stop characters shall have the same bar-space sequence for all rows.

Figure 4 — PDF417 Start and Stop Characters
4.4 High level (data) encodation
High level encoding converts the data characters into their corresponding codewords.
Data compaction schemes shall be used to achieve high level encoding. Three modes are defined below, each of
which defines a particular efficient mapping between user defined data and codeword sequences. PDF417 has
three data compaction modes:
• Text Compaction mode (see 4.4.2).
• Byte Compaction mode (see 4.4.3).
• Numeric Compaction mode (see 4.4.4).
A given string of data bytes may be represented by different codeword sequences, depending on how the encoder
switches between compaction modes and sub-modes. There is no single specified way to encode data in a
PDF417 symbol.
900 codewords are available in each mode for data encodation and other functions within the mode. The
remaining 29 codewords are assigned to specific functions (see 4.4.1) independent of the current compaction
mode.
PDF417 also supports the Extended Channel Interpretation system, which allows different interpretations of data to
be accurately encoded in the symbol (see 4.5).
10 © ISO/IEC 2001 – All rights reserved

4.4.1 Function codewords
Codewords 900 to 928 are assigned as function codewords as follows:

• for switching between modes (see 4.4.1.1)
• for enhanced applications using Extended Channel Interpretations (ECIs) (see 4.4.1.2)
• for other enhanced applications (see 4.4.1.3 and 4.4.1.4).
At present codewords 903 to 912 and 914 to 920 are reserved. Table 2 defines the complete list of assigned and
reserved function codewords. Their functions are defined in 4.4.1.1 to 4.4.1.4. See 4.4.6 for the treatment of
reserved codewords.
Table 2 — Assignments of PDF417 Function Codewords
Codeword Function Refer to Section
900 mode latch to Text Compaction mode 4.4.1.1
901 mode latch to Byte Compaction mode 4.4.1.1
902 mode latch to Numeric Compaction mode 4.4.1.1
903 to 912 Reserved
913 mode shift to Byte Compaction mode 4.4.1.1
914 to 920 Reserved
921 reader initialisation 4.4.1.4
922 terminator codeword for Macro PDF control block 4.13
923 sequence tag to identify the beginning of optional fields in 4.13
the Macro PDF control block
924 mode latch to Byte Compaction mode (used differently from 4.4.1.1
901)
925 identifier for a user defined Extended Channel Interpretation 4.5
(ECI)
926 identifier for a general purpose ECI format 4.5
927 identifier for an ECI of a character set or code page 4.5
928 Macro marker codeword to indicate the beginning of a Macro 4.13
PDF Control Block
4.4.1.1 Function codewords for mode switching
In one PDF417 symbol it is possible to switch back and forth between modes as often as required. Advice about
selecting the appropriate modes is given in 4.4.5.
A mode latch codeword may be used to switch from the current mode to the indicated destination mode which
stays in effect until another mode switch is explicitly brought into use. Codewords 900 to 902 and 924 are
assigned to this function. Table 3 defines their function.
The mode shift codeword 913 shall cause a temporary switch from Text Compaction mode to Byte Compaction
mode. This switch shall be in effect for only the next codeword, after which the mode shall revert to the prevailing
sub-mode of the Text Compaction mode. Codeword 913 is only available in Text Compaction mode; its use is
described in 4.4.2.4.
© ISO/IEC 2001 – All rights reserved 11

Table 3 — Mode Definition and Mode Switching Codewords
Destination Mode Mode Latch Mode Shift
Text Compaction 900
Byte Compaction 901/924 913
Numeric Compaction 902
NOTE: The table identifies the codeword which shall be used to switch to the defined mode.
The switching rules between the three modes are defined in Table 4 and shown schematically in Figure 5.

Table 4 — Mode Transition Table, Showing Codewords and Their Function
Original Mode
Destination Mode
Text Byte Numeric
Text 900 mode latch 913 mode shift 902 mode latch
901 mode latch
924 mode latch
Byte 900 mode latch 901 mode latch 902 mode latch
924 mode latch
Numeric 900 mode latch 901 mode latch 902 mode latch
924 mode latch
12 © ISO/IEC 2001 – All rights reserved

Figure 5 — Available Mode Switching

The switching rules into Byte Compaction mode are more fully defined in 4.4.3.1.

4.4.1.2 Function codewords for switching to Extended Channel Interpretations
An ECI codeword can be used to switch to a particular interpretation, which stays in effect until another ECI
codeword is explicitly brought into use or until the end of the data. Codewords 925 to 927 are assigned to this
function (see 4.5).
4.4.1.3 Function codewords for Macro PDF417
Macro PDF417 symbols (see 4.13) shall use Codeword 928 at the start of the Macro PDF417 Control Block.
Codewords 922 and 923 are used for special functions in Macro PDF417.

4.4.1.4 Function codeword for reader initialisation
Codeword 921 shall be
...