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Transition Guide for the ® dsPIC /PIC24 Compiler

CCS PCD Compiler
revised: 25-JUL-07

DATA
The PCD compiler defaults an int to a int16. A short is 8 bits and a long is 32 bits. In additionthe default for all ints is SIGNED. To make the types work in PCD the way they do in the other CCS compilers use: #TYPE CLASSIC The PCD compiler adds the integer types int48 and int64. In addition thereare two new floattypes float48 and float64 (aka double). The float32 (aka float) format has been changed in PCD to use the IEEE format instead of the Microchip format. This is the same formatMicrochipuses in their C30 compiler.

SPECIFICS

Code size and run time will be most effective if you stick with only one float type throughout your program. The 24-bit opcode parts work best when dealing withan int16. There is an additional overhead in most cases when doing an int8 operation. Many built in functions that returned an int8 value in the other CCS compiler now return an int16. The 24-bitopcode parts do not have RAM banking like the other PIC parts. The first 8K of RAM can be equally accessed by most instructions and the remaining RAM can only be accessed by a less efficient means. For DSPwork RAM is split into two areas (X and Y). The #BANKX and #BANKY directives are used to put variables into a specific area. DSP instructions require certain operands to be in a particular area.ASSEMBLY
SPECIFICS SPECIFICS
The assembly instructions do not resemble the traditional PIC instructions. The compiler inline assembly feature will accept assembly in the published Microchip format.In PCW use OPTIONS > PROJECT OPTIONS > FILE FORMATS to select “Interpret” and an interpretation of the assembly instructions will be added to the LST file. This can be helpful to those not expert in theassembly. This can be especially helpful for instructions that use implied registers. In the same window the SFR option can be used to show the Special Function Register names in the LST file....