Technical information

Operating Precautions for CPDW9X/NT-CDR-V85X, Y-GHS-MULTI-V800

Customer Notification r20tu0003ed1812 47

No. a33

The use of the bit instruction NOT1 is not systematic in XOR operation

Version Information

V3.5

Details

when compiling C code using the ^ (xor) bit operation with size optimization,

the assembly instruction NOT1 is not used in all cases, although its use will

reduce the code size.

Example:

test.c

struct bitf {

unsigned char bit00:1;

unsigned char bit01:1;

unsigned char bit02:1;

unsigned char bit03:1;

unsigned char bit04:1;

unsigned char bit05:1;

unsigned char bit06:1;

unsigned char bit07:1;

unsigned char bit08:1;

unsigned char bit09:1;

unsigned char bit10:1;

unsigned char bit11:1;

unsigned char bit12:1;

unsigned char bit13:1;

unsigned char bit14:1;

unsigned char bit15:1;

};

// bit 3 of port 5

#define P53 ((volatile struct bitf *)0xfffff40a)->bit03

// Port 5 register

#define P5 *((volatile unsigned char *)0xfffff40a)

void main(void)

{

P5 ^= 0x08;

P53 ^= 1;

}

Command Sequence

ccv850e -OS -S test.c