IBM 4400 User Manual
242
Chapter
7
Bar Codes
PDF 417
The PDF417 structure is shown in Figure 18 and described below.
Figure 18. PDF417 Structure
Quiet Zone
Both ends of the bar code structure require blank quiet zones. The quiet
zones must be at least 0.25 inches wide and completely blank to ensure
accurate reading of the start/stop codes and to prevent adjacent bar codes
from overlapping. Be sure to provide sufficient space on the form for the quiet
zones.
zones must be at least 0.25 inches wide and completely blank to ensure
accurate reading of the start/stop codes and to prevent adjacent bar codes
from overlapping. Be sure to provide sufficient space on the form for the quiet
zones.
Start/Stop Codes
The start/stop codes identify the leading and trailing end of the bar code.
Data Field
PDF417 provides twelve modes to encode data. The first three are pre-
established (the remaining nine are user modes, which can be defined by
users or industry associations according to specific applications):
established (the remaining nine are user modes, which can be defined by
users or industry associations according to specific applications):
1.
Extended Alphanumeric Compaction mode (EXC). Comprised of four
sub-modes, this mode offers encodation of all printable ASCII characters.
This is the default mode; ASCII Emulation uses shift or latch characters to
enable other modes.
sub-modes, this mode offers encodation of all printable ASCII characters.
This is the default mode; ASCII Emulation uses shift or latch characters to
enable other modes.
2.
Binary/ASCII Plus mode. This offers encodation for all ASCII characters,
printable or not, and binary values.
printable or not, and binary values.
3.
Numeric Compaction mode. This offers encodation for numeric values to
a density of almost 3 digits per code word.
a density of almost 3 digits per code word.
ASCII Emulation will automatically switch between modes to provide the
smallest encodation for the data.
smallest encodation for the data.
Security Level
PDF417 can detect and correct errors. Each label has 2 code words of error
detection. You can select the error correction capacity based on application
needs. Specify a security level in the range of 0 - 8, at the time of printing.
PDF417 can also recover from omissions and misdecodes of code words.
Since it requires two code words to recover from a misdecode, one to detect
detection. You can select the error correction capacity based on application
needs. Specify a security level in the range of 0 - 8, at the time of printing.
PDF417 can also recover from omissions and misdecodes of code words.
Since it requires two code words to recover from a misdecode, one to detect
DATA FIELD
QUIET
ZONE
ZONE
QUIET
START
CODE
CODE
ZONE
STOP
CODE
CODE
LOWER GUARD BAND
UPPER GUARD BAND
SR, SC
POSITION