SW006012 Microchip Technology, SW006012 Datasheet - Page 207

• Manufacturer Part Number: SW006012
• Description: C COMPILER FOR DSPIC30F FAMILY
• Manufacturer: Microchip Technology
• Type: MPLAB® C30 Compilerr
• Series: PIC24 & DsPICr

Specifications of SW006012

• Supported Families: PIC24, DsPIC30F And DsPIC33F
• Core Architecture: PIC, DsPIC
• Kit Contents: Software And Docs
• Mcu Supported Families: PIC24 MCUs And DsPIC DSCs
• Tool Type: Compiler
• Processor Series: PIC24, dsPIC
• Lead Free Status / RoHS Status: Not applicable / Not applicable
• For Use With/related Products: dsPIC30F
• Lead Free Status / Rohs Status: Lead free / RoHS Compliant

D.21 BIT FIELDS
© 2007 Microchip Technology Inc.
Bit fields in MPLAB C18 cannot cross byte storage boundaries and, therefore, cannot
be greater than 8 bits in size.
MPLAB C30 supports bit fields with any bit size, up to the size of the underlying type.
Any integral type can be made into a bit field. The allocation cannot cross a bit boundary
natural to the underlying type.
For example:
struct foo will have a size of 10 bytes using MPLAB C30. i will be allocated at bit
offset 0 (through 39). There will be 8 bits of padding before j, allocated at bit offset 48.
If j were allocated at the next available bit offset, 40, it would cross a storage boundary
for a 16 bit integer. k will be allocated after j, at bit offset 64. The structure will contain
8 bits of padding at the end to maintain the required alignment in the case of an array.
The alignment is 2 bytes because the largest alignment in the structure is 2 bytes.
struct bar will have a size of 8 bytes using MPLAB C30. I will be allocated at bit
offset 0 (through 39). There is no need to pad before J because it will not cross a
storage boundary for a char. J is allocated at bit offset 40. K can be allocated starting
at bit offset 48, completing the structure without wasting any space.
struct foo {
} x;
struct bar {
} y;
long long i:40;
int j:16;
char k:8;
long long I:40;
char J:8;
int K:16;
MPLAB C18 vs. MPLAB C30 C Compiler
DS51284F-page 201