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

#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"

Code:

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

  Shift by 4 bits at a time

  "

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Peter Todd has released source and sample projects for his artwork, including his 3d wireframe cube renderer for the PIC 18f6520 This includes examples of hardware developed with free software tools such as gEDA/gschem/PCB, SDCC, gputils and picp all on Linux. http://petertodd.ca/art/source-code/

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