Appendix F - Deviations

Code 93 uppercase vs. lowercase

The Forms and Bar Code Card firmware converts any Code 93 lowercase input to uppercase before submission to the BCE. This firmware generates the proper uppercase characters within the bar code.

Notes:

• The Code 93 bar code uses the same encoding as Code 39.
• HP BarDIMM Pro and Forms and Bar Code Card converts lowercase “a” to “z” character input to uppercase, and the bar code scan contains only uppercase.
• The HRT is printed as lowercase, reflecting the input data, rather than the actual bar code encoded data.
• The BCE does not support lowercase “a” to “z” character input, does not convert to uppercase, and operates according to the specifications noted previously.

Codabar uppercase vs. lowercase

The Forms and Bar Code Card firmware converts any Codabar lowercase start and stop input to uppercase before submission to the BCE. This firmware generates the proper uppercase start and stop bar code characters.

Notes:

• The Codabar bar code uses two bar and space widths—narrow and double-wide. The single narrow inter-character space separates each character that contains exactly four bars and three spaces. Due to the encoding, each bar code character width may vary slightly depending on the character being encoded. A single start and stop brackets the numeric data encoded within the bar code.
• HP BarDIMM Pro and Forms and Bar Code Card convert lowercase start and stop character input to uppercase. The bar code image is encoded with uppercase characters for the start and stop characters.
• The HRT start and stop characters are printed as lowercase, reflecting the input data, rather than the actual bar code encoded data.
• The BCE does not support lowercase "a" to "z" start and stop character input, and does not convert to uppercase. It also does not operate according to the specifications noted previously.

Maximum encodable character length

The BCE allocates memory for a requested bar code on a per-symbology basis. It does not allocate memory on a symbol-by-symbol basis as it builds the bar code. Rather, it allocates the entire memory block needed at once for each bar code it generates. It uses this technique to reduce the overhead of memory allocation and ensure good performance.

Because the BCE allocates a finite amount of memory per bar code, input data with a large amount of encodable data generates a garbled bar code image. The image does not have well-formed bars and spaces, or sometimes, the data generates a code 19 NotEnoughMemory error.

The commercially viable limit for a typical one-dimensional bar code is 20–25 characters. Large bar codes may not fit on the page, or the reliability of the scan may decline with a large amount of encoding data. However, the BCE still attempts to encode this data until the image fails. There is no warning or error associated with garbled images generated by a large amount of data.

The maximum amount of input data is shown in the table. This table is just a guide and changes depending on the following assumptions:

• Amount of RAM in the printer

• Version of the BCE

• Compiler or linker used

4-State postal widths

The BCE creates 4-State postal images that are slightly different from HP BarDIMM Pro and Forms and Bar Code Card images. However, a change in the BCE to address this difference may be implemented in a later version.

HRT widths and heights

The BCE uses the FreeType font renderer with custom SuchyMIPS-generated fonts to produce the HRT on bar codes. Sometimes, the HRT may differ in size or may not be positioned exactly as on HP BarDIMM Pro or Forms and Bar Code Card. However, the HRT should be readable, legible, and approximately the same as the target platforms.

PDF417 image widths and heights

The BCE generates PDF417 images based on the algorithms found in the AIM PDF417 specification. The implementation of a PDF417 image can differ between manufacturers, depending on the interpretation of the specification.

Because of this specification, some character length and ECC level combinations can produce images that differ from HP BarDIMM Pro or Forms and Bar Code Card. These images differ slightly in the number of rows and columns.

A typical example is a PDF417 image with the following characteristics:

• Character string "ABCDEFGHIJ"

• An ECC level of 3

• Automatic rows and columns specified

• Aspect ratio of 1.0 to 2.0

• PCL string: ^Esc (s3p2,1s24850TABCDEFGHIJ

The results are the following:

• HP BarDIMM Pro and Forms and Bar Code Card create an image with 2 columns and 11 rows.

• The BCE creates an image with 1 column and 22 rows.

• The data scanned by a symbol verifier from all three images is correct.

This deviation is rare. When it does occur, it should not result in the loss of data that can be scanned.

MaxiCode capacity

The AIM MaxiCode specification defines the codewords that can be encoded. For more information, see Mode: (Default = 02x) .

• A Mode 4 symbol holds 93 codewords.

• A Mode 5 symbol holds 77 codewords.

• The Mode 6 symbol capacity is not specified, but it should be the same as Mode 4 (no error correction).

The original Forms and Bar Code Card encodes more than the maximum amount allowed by the AIM specification, but users must never exceed these values. Also, not all bar code readers can decode data more than the maximum allowed in the AIM MaxiCode specification.

Bar code horizontal alignment

Some UPC and EAN bar codes do not start at the existing PCL emulation cursor position. These bar codes are shifted up to 3–4 mm on the left side and up to 2 mm on the right side. These instances are due to the presence of start characters, which may or may not shift the bar code (and HRT) to the right.

If you allocate space for these particular bar codes, and they do not fit on the right side, then there are two options:

• Use the PCL emulation B and S parameters to shrink the bar code in size.

• Escalate the issue for a field fix.

PDF417 capacity

The introduction of the AIM PDF417 specification defines the maximum data characters per symbol (at ECC0) for PDF417:

• 1850 text characters

• 2710 digits

• 1108 bytes

The total number of codewords in the data region of a single PDF417 symbol cannot exceed 928.

All input data must conform to the AIM PDF417 specification, and any input data over the maximum length must be truncated and discarded. The firmware allows and truncates a maximum of 2710 digits or 1850 text characters. The remaining maximum data is submitted to the BCE to be rendered.

However, extra checking code is required to truncate excess data while encoding codes that are within the limit.

The original Forms and Bar Code Card encodes more than the maximum amount allowed by the AIM specification, but users must never exceed these values. Also, not all bar code readers can decode data more than the maximum allowed in the AIM PDF417 specification.

MaxiCode separators and structured appends

A valid MaxiCode data separator for MaxiCode data blocks is either of the following:

• Group separator—29 decimal (1D hexadecimal)

• Comma—44 decimal (2C hexadecimal)

MaxiCode typeface call method

A structured append is covered in the AIM MaxiCode specification, which allows up to eight MaxiCode symbols to be chained together as one. However, there are no bar code readers that can decode combined bar code series.

SuchyMIPS and HP BarDIMM Pro support structured appends so they can parse the structured append, but they do not fully implement it.

A structured append consists of four bytes:

• A number 1 through 8 that labels each individual MaxiCode in the structured append

• A separator character, either a comma or group separator (ASCII 29)

• A number 1 through 8 that is the maximum number of MaxiCode symbols in the structured append

• Another separator character

For example, the only valid MaxiCode that is supported is a single symbol, specified as the following:

1,1,01234567...... where 1,1, represents the structured append and 01234567.... represents the rest of the MaxiCode data structure.

The HP BarDIMM Pro specification version 3.0 and later is consistent with this PCL emulation data stream calling sequence:

<Esc>(s24800T1,1, x ,01234567..... where x is either a 2 or 3, corresponding to MaxiCode Mode 2 or Mode 3.

Mode 2 encodes numeric-only data, and Mode 3 allows a reduced amount of alphanumeric data.

The mode of the MaxiCode is specified within the input data after the typeface command 24800T . If the two extra bytes (Mode 2 or 3 plus a separator) are included in the input data, then the BCE shows an error.

Users must add more parsing that examines input data:

• Byte 5 for either a 2 or 3

• Byte 6 for a separator character

If the extra bytes are found, then remove them, and pass the four structured append bytes and the rest of the input data to the BCE. This method still allows existing HP-coded data streams to work on HP BarDIMM Pro, while allowing Forms and Bar Code Card to work correctly.

MaxiCode block call method

The minimum amount of input data to invoke a MaxiCode starts with this command:

1B 26 78 33 57

00 02

This command includes the following:

• ^Esc & x 3 W (block bar code PCL emulation call, with 3 following command bytes)

• 0002 (the MaxiCode symbology identifier)

• One or more of these data blocks (one per MaxiCode symbol):

  • 1B 26 79 34 57

  • 31 1D 31 1D

  • 31 2C 31 2C

  These data blocks include the following:

  • ^Esc & y 4 W (data bar code PCL emulation call, with 4 following data bytes)

  • 1 GS 1 GS or 1, 1,

  A valid MaxiCode data separator for the previous data block is either of the following:

  • Group separator—29 decimal (1D hexadecimal)

  • Comma— 44 decimal (2C hexadecimal)

  Any other separator characters produce an error on the page.

MaxiCode separator change

A valid MaxiCode with any encodable data requires a second separator for the PCL emulation block call, and is placed after the number-of-labels field.

If the four-byte structured append is specified alone, then Forms and Bar Code Card prints a valid MaxiCode symbol that is empty. Depending on the scanner used, Forms and Bar Code Card may not produce a valid scan.

If an outdated three-byte structured append is specified alone, then Forms and Bar Code Card shows an error.

Encoding limits for bar codes

This deviation concerns firmware-imposed limits on certain bar codes. These limits are less than the original Forms and Bar Code Card, but are needed to prevent corruption of bar code images.

This table details the new limits:

Encoding limits for Codabar bar codes

In the absence of start and stop characters, if users encode a Codabar bar code with non-numeric characters, then !Err: 12 Invalid Character appears.

When using the optional start and stop characters, characters between the start and stop characters must be numeric, or any of the following non-numeric characters: - $ : / +

Otherwise, !Err: 12 Invalid Character appears.

If a user encodes a Codabar bar code with only one numeric character, then a Codabar bar code is generated. However, if a user encodes a Codabar bar code with no characters, then !Err: 15 String too Short appears.

PostScript emulation barcodepath operator

The barcodepath operator is used to obtain the outline of the bar code that results from doing a barcodeshow with the same arguments. Because all bar codes are now generated as images, the barcodepath operator does not return any useful information.

Any further use of the barcodepath operator must be discontinued.

Uploading formsets when the OFIS data filter is disabled

When the OFIS data filter is disabled, uploading formsets that contain OFIS tags to Forms Manager results in either of the following:

• If the Print PS Error setting of the printer is turned on, then an error page prints and the job is flushed. The printer returns to Ready state.

• If the Print PS Error setting of the printer is turned off, then the job is flushed and the printer returns to Ready state.

French Postal 3 of 9 dimensions

This bar code is based on Code 3 of 9 with a checksum digit, and is used on registered letters.

The BCE and HP BarDIMM Pro generate a default 3 of 9 bar code that is 79 mm wide. Forms and Bar Code Card generates a smaller bar code that is about 63 mm wide.