PicC 9.50 dsPIC Manual.pdf

CrefLinker and Utilities5.11.1 Checksum SpecificationsThe checksum specification allows automated checksum calculation. The checksum specificationtakes the form of several lines, each line describing one checksum. The syntax of a checksum lineis:addr1-addr2 where1-where2 +offsetAll of addr1, addr2, where1, where2 and offset are hex numbers, without the usual H suffix.Such a specification says that the bytes at addr1 through to addr2 inclusive should be summedand the sum placed in the locations where1 through where2 inclusive. For an 8 bit checksumthese two addresses should be the same. For a checksum stored low byte first, where1 should be lessthan where2, and vice versa. The +offset is optional, but if supplied, the value offset will be usedto initialise the checksum. Otherwise it is initialised to zero. For example:0005-1FFF 3-4 +1FFFThis will sum the bytes in 5 through 1FFFH inclusive, then add 1FFFH to the sum. The 16 bitchecksum will be placed in locations 3 and 4, low byte in 3. The checksum is initialised with 1FFFHto provide protection against an all zero ROM, or a ROM misplaced in memory. A run time check ofthis checksum would add the last address of the ROM being checksummed into the checksum. Forthe ROM in question, this should be 1FFFH. The initialization value may, however, be used in anydesired fashion.5.12 CrefThe cross reference list utility CREF is used to format raw cross-reference information produced bythe compiler or the assembler into a sorted listing. A raw cross-reference file is produced with the--CR option to the compiler. The assembler will generate a raw cross-reference file with a -C option(most assemblers) or by using an OPT CRE directive (6800 series assemblers) or a XREF control line(PIC assembler). The general form of the CREF command is:cref options fileswhere options is zero or more options as described below and files is one or more raw crossreferencefiles. CREF takes the options listed in Table 5.5.Each option is described in more detail in the following paragraphs.108