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Chapter 4. Record Formats<br />
Character Definition Record (CDR)<br />
Character Definition Record (CDR)<br />
CDR records follow the FDR record and define each character in the font.<br />
The CDRs contain the bitmap patterns for the characters. Up to 256<br />
characters can be defined for each FDR. Usually, there is one CDR for<br />
each character. However, in some fonts, a continuation CDR is used to<br />
divide a character bitmap into two or more records if it is necessary to limit<br />
the size of the records (because of block length restrictions or other<br />
reasons). The character bitmap can be broken only at the end of a row.<br />
When continuation CDRs are used, all fields up to the bitmap pattern field<br />
must be the same in each CDR for the character except for the<br />
continuation bit in the last CDR.<br />
Note: As an option, a single CDR may immediately follow an SFD to define the<br />
default character for any undefined character in the super font.<br />
When an FDR is received, the printer defines null and default characters<br />
in the following manner. When an FDR is first processed by the printer, all<br />
256 characters in the font are set as null characters. If the first CDR<br />
received has a hex 00 in the Character Identifier field, then the character<br />
in this record is used as the default character for character identifiers hex<br />
01 through FF (character 00 remains a null character). Subsequent CDRs<br />
then redefine the characters for their respective character identifiers.<br />
Character 00 can be redefined from the null character in this manner. If<br />
the first CDR does not have a hex 00 in the Character Identifier field, then<br />
all characters remain null until redefined by subsequent CDRs.<br />
A null character has zero width, and takes no space when printed.<br />
Note: An example of FDR and CDR coding is shown in Appendix B.<br />
Byte Position Bytes Field Name Description<br />
1-2 2 Record Length The length of this record, in binary, including the record length<br />
field. For example, hex 00 8C specifies a record length of 140<br />
bytes.<br />
3 1 Cyclic Record Count A binary cyclic record count using modulo 256. Each record in the<br />
job is counted, starting with hex 01 for the first record. The 255th<br />
record is hex FF and the 256th record is hex 00. This count is used<br />
to verify record sequence.<br />
4 1 Control Code A binary code that identifies the record type. A value of hex 14<br />
identifies the CDR record.<br />
5 1 Character Identifier A binary code that identifies the character defined in this record.<br />
This is the code that must be used in the input data to access this<br />
character for printing. The range is 0 - 255.<br />
6 1 Equivalent Character<br />
Identifier<br />
A binary code that identifies a character in the font that has a<br />
bitmap pattern identical to this character. If 2 characters are the<br />
same, it is not necessary to repeat the bitmap pattern. The<br />
“Equivalent” bit in byte position 8 must be set for this field to be in<br />
effect.<br />
If the equivalent bit is set, the character defined in this field is part<br />
of the font currently being defined unless another font is identified<br />
in byte 9 or in bytes 9 and 10. If byte 9 identifies a regular font,<br />
then byte 10 (if present) is ignored. If byte 9 identifies a super font,<br />
then byte 10 must be present and identifies the subfont. In any<br />
case, the character must have been previously loaded in the same<br />
RIP.<br />
Reference Guide 4 - 23
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