PCWHD IDE COMPILER Custom Computer Services Inc (CCS), PCWHD IDE COMPILER Datasheet - Page 63

• Manufacturer Part Number: PCWHD IDE COMPILER
• Description: PCWHD PIC10,16,18,24, DSPIC
• Manufacturer: Custom Computer Services Inc (CCS)
• Type: Compilerr

Specifications of PCWHD IDE COMPILER

• For Use With/related Products: Microchip PIC10, PIC12, PIC16, PIC18, PIC24, dsPIC MCUs
• Lead Free Status / RoHS Status: Not applicable / Not applicable
• Other names: 429-1009

Using Program Memory for Data
CCS C Compiler provides a few different ways to use program memory for data. The different ways
are discussed below:
Constant Data:
The CONST qualifier will place the variables into program memory. If the keyword CONST is used
before the identifier, the identifier is treated as a constant. Constants should be initialized and may
not be changed at run-time. This is an easy way to create lookup tables.
The ROM Qualifier puts data in program memory with 3 bytes per instruction space. The address
used for ROM data is not a physical address but rather a true byte address. The & operator can be
used on ROM variables however the address is logical not physical.
The #org preprocessor can be used to place the constant to specified address blocks.
The function label_address can be used to get the address of the constant. The constant variable
can be accessed in the code. This is a great way of storing constant data in large programs.
Variable length constant strings can be stored into program memory.
A special method allows the use of pointers to ROM. This method does not contain extra code at
the start of the structure as does constant.
The compiler allows a non-standard C feature to implement a constant array of variable length strings.
Where n is optional and id is the table identifier.
The syntax is:
For example:
Placing data into ROM
Placing a string into ROM
Creating pointers to constants
For example:
The constant ID will be at 1C00.
Note: Some extra code will precede the 123456789.
For example:
The syntax is:
For example:
const type id[cexpr] = {value}
const int table[16]={0,1,2...15}
const char cstring[6]={"hello"}
const char *cptr;
cptr = string;
#ORG 0x1C00, 0x1C0F
CONST CHAR ID[10]= {"123456789"};
char rom commands[] = {“put|get|status|shutdown”};
const char id[n] [*] = { "string", "string" ...};
const char colors[] [*] = {"Red", "Green", "Blue"};
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