ijpds formats.book - Kodak

Chapter 4. Record Formats
Verify Character Checksum (VCC)
Verify Character Checksum (VCC)
The VCC record is used to verify the data written to each page buffer. The
printer starts calculating a checksum value at the start of each page and
continues until the end of the page. When the VCC record occurs, the
checksum value in the record is compared to the current checksum value
calculated by the printer. If the two checksums do not agree, the printer
does a fast stop operation. The VCC record may appear several times in
the data stream for one page. For a multiple RIP, the checksum is
calculated independently for each page for each RIP.
Byte Position Bytes Field Name Description
1-2 2 Record Length The length of this record, in binary, including the record length
field. For example, hex 00 08 specifies a record length of 8 bytes.
3 1 Cyclic Record Count A binary cyclic record count using modulo 256. Each record in the
job is counted, starting with hex 01 for the first record. The 255th
record is hex FF and the 256th record is hex 00. This count is used
to verify record sequence.
4 1 Control Code A binary code that identifies the record type. A value of hex 2D
identifies the VCC record.
5-8 4 Checksum A value calculated by the printer in the printing system as
described below.
4 - 60 IJPDS Formats
The character checksum is calculated as follows:
The checksum is set to 0 by the printer at the start of each page.
As each character printed by an SFI, IML, SIL, or UIL record is placed
into the page buffer, its character value is added to the character
checksum for the page. Only the least significant 32 bits of the
checksum is retained and checked.
For a single-byte font, the character value is an 8-bit number calculated
as follows:
Character value = (character position + font number) modulo 256.
Where:
Character position = character identifier specified in CDR/CDM/CCD.
Font number = number specified in FDR/FDM.
For a double-byte font, the character value is an 8-bit number calculated
as follows:
Character value = (character position + subfont number + super font
number) modulo 256.
Where:
Character position = character identifier specified in CDR.
Subfont number is the number specified in FDR.
Character position + subfont number = the sum of the two bytes in the
character identifier in CDM/CCD.
Superfont number is the number specified in SFD/SFM.