Register Layout

       While the 68HC11 is 8 bit register results,  16 bit functions such as

      16 / 16 bit divides are supported by the use of double size registers

The 68HC11 supports the following instructions:

Addition

for both 8-bit and 16-bit values.

Subtraction

for both 8-bit and 16-bit values.

Multiplication

of two 8-bit values to yield a 16-bit result.

Division

of two 16-bit values to yield an integer or fractional result.

Increment

of both 8-bit and 16-bit values. The increment operation adds one to its operand.

Decrement

of both 8-bit and 16-bit values. The decrement operation subtracts one from its operand.

Bitwise AND

for 8-bit values. This instruction performs a bit-wise "and" operation on two pieces of data. The result of an AND operation is 1 if and only if both of its operands are 1. (e.g., %11110010 ANDed with %11000011 yields %11000010).

Bitwise OR

for 8-bit values. This instruction performs a bit-wise "or" operation on two pieces of data. The result of an OR operation is 1 if either or both of its operands is 1.

Bitwise Exclusive OR

for 8-bit values. The result of an exclusive-OR operation (called "EOR") is 1 if either, but not both, of its inputs are 1.

Arithmetic Shift operations

on 8-bit and 16-bit values. The Arithmetic Shift operation moves all the bits in an operand to the left or to the right by one bit position. This is equivalent to a multiplication or division by 2 (respectively) upon the operand.

Rotation operations

on 8-bit values. These are similar to the shift operations except that the bit that gets shifted out of the high or low bit position (depending on the direction of the rotation) gets placed in the bit position vacated on the other side of the byte. Example: rotate right (ROR) of %11011001 produces %11101100.

Bitwise Set and Clear operations

on 8-bit values. These operations set or clear bits at specified bit positions within an eight-bit data byte.

Clear operations

on 8-bit memory bytes or registers. This instruction is equivalent to writing a zero into the memory location or 68HC11 register but does so more quickly.

Jump/Branch operations are similar to the 8051 but with an addition of  inequality operators.

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