6800 Data Manipulation Instructions

·  Addition is done by insert one number to the accumulator and then added it with another number by using ADD instruction.

·   Memory content are added with content of accumulator and result of addition will store into accumulator.

·   This instruction have three (3) addressing mode which is immediate, direct and extended.

·   Arithmetic operation will change value of flag N, Z, V, and C.  By checking C bit in CCR after addition, borrow value can be check.  If borrow value produce by before operation, so C flag will be set.

·   6800 is a 8-bit microprocessor, so it can handle only 255 maximum number.  The bigger number can be handle by using more than one byte memory.  Value of two byte can be store until 65,535 and three byte can be store until 16,777,215.

·   Number with multiple byte is store in side-by-side position.

·   In arithmetic multiple byte, the operation start at the lower byte and the carry value will be used in the operation on the upper byte.

·   The operation of ADC (Add to accumulator with carry) instruction are same as ADD instruction operation.  The differences are carry bit from lower byte operation are add to the current addition process (or upper byte).  This instruction have three (3) addressing mode which is immediate, direct and extended.

·   Subtraction operation have been done by using SUB (subtract from accumulator) and SBC (subtract from accumulator with carry).  SUB Instruction operation are not involve Carry flag.  SBC instruction will subtract 1 from result if C flag are set 1, if not their effect are same as SUB instruction operation.

·   The value in accumulator A can be added with value in accumulator B and their result store at accumulator A by using ABA (Add ACCB to ACCA) instruction also value in accumulator A can be subtract from accumulator B by using SBA (subtract ACCB from ACCA) instruction.

·   Another arithmetic instruction are NEG (Negate), CLR (Clear), INC (Increment) and DEC (Decrement).  NEG instruction are using for get the 2 complement’s operand.  CLR instruction are used to put zero value to the destination of the operand.  INC instruction are used to added 1 to the operand to get the address of the operation where else DEC instruction are used to subtract 1 from the operand.