SW500010 Microchip Technology, SW500010 Datasheet - Page 105

• Manufacturer Part Number: SW500010
• Description: HI-TECH C PRO FOR PIC10/12/16
• Manufacturer: Microchip Technology
• Type: Compilerr
• Series: PIC10/12/16r

Specifications of SW500010

• Supported Families: PIC10, PIC12, PIC16
• Core Architecture: PIC
• Software Edition: Professional
• Kit Contents: Software And Docs
• Mcu Supported Families: PIC10/12/16
• Tool Type: Compiler
• Lead Free Status / RoHS Status: Not applicable / Not applicable
• For Use With/related Products: PIC10, PIC12, PIC14, PIC16, PIC16E
• Lead Free Status / Rohs Status: Lead free / RoHS Compliant
• Other names: 019P; 778-1006; 778-1006

C Language Features
3.10.4.2 Undefined Symbols
Variables can be defined in assembly code if required, but in some instances it is easier to do so in
C source code, in other cases, the symbols may need to be accessable from both assembly and C
source code.
the entire the C program. In this case, the code generator may remove the variable believing it is
unused. If assembly code is relying on this definition an error will result.
assembly-derived object files for symbols which are undefined. These will typically be symbols that
are used, but not defined, in assembly code. The code generator is informed of these symbols, and if
they are encountered in the C code the variable is automatically marked as being volatile. This is the
equivalent of the programmer having qualified the variable as being volatile in the source code,
see Section 3.3.9. Variables qualified as volatile will never be removed by the code generator,
even if they appear to be unused throughout the program.
A problem can occur if there is a variable defined in C code, but is never referenced throughout
To work around this issue, HI-TECH C PRO for the PIC10/12/16 MCU Family also searches
generator to ensure that these address spaces are not used by C code. The linker will
also be told to remove these ranges from those available, and this reservation will be
observable in the map file. The RAM class definition, for example, may look like:
-ARAM=020-06Fh,0A0h-0EFh,130h-16Fh,0190h-01EFh
for an 16F877 device, showing that addresses 110h through 12F were reserved from this
class range.
T
P
as follows:
int input;
but this variable is only ever used in assembly code. The assembly module(s) can simply
declare and link in to this symbol using the GLOBAL assembler directive, and them make
use of the symbol.
GLOBAL _input
PSECT text,class=CODE,delta=2
movf _input,w
In this instance the C variable input will not be removed and be treated as if it was
qualified volatile.
UT RIAL
ROCESSING OF UNDEFINED SYMBOLS
A C source module defines a global variable
Mixing C and Assembler Code
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