PIC Microcontoller Bit Math Methods

• Copy aligned bits from one register to another
• Copy unaligned bits from one register to another:
• Transfer one bit from a file register to one pin of PORT w/o jitter
• Converting a 2-bit number to a 4-bit mask
• Converting a 3-bit number to a 8-bit mask
• Parity
• Cyclic Redudancy Check (CRC)
• Reverse bit order in a byte
• Setting bit number X
• Toggle or NOT bit number X
• Which bit number was set?
• Counting how many bits are set
• Testing bits in W
• Clear W, Set bits
• Rotate without carry
• Rotate the nibbles within a byte.
• Rotate some bits without affecting others
• Swap two bits in a register
• AND two bits in a register
• OR two bits in a register
• swap w and f without a temp register
• big shifts
• Sum two bits from different positions and registers
• Detecting bit changes
• Complement the carry flag: incf STATUS, f
• Rotate a byte a variable number of positions

#define BIT(addr,bit) bit
#define ADDR(addr,bit) addr
#define MASK(addr,bit) 1<<(bit) 
Then: 
#define myflag somereg,5 

	movlw BIT(myflag) 
	movf ADDR(myflag),w 
	andlw MASK(myflag) 
etc... 

Techniques for exploiting the parallelism of bitwise operations [incl bit reversals, counting, and Morton keys] by Ron Gutman

Archive:

• PICList post "Challenge: Shifting by a variable amount"
• PICList post "restricting the range of FSR by bit skip and clear/set"

See:

Code:

• mark_jeronimus-gmail- shares this code: " /techref/microchip/math/bit/shift4.htm

  Shift by 4 bits at a time

  "

  +

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