Source (Packed BCD) + adjustment -->;
Destination (Unpacked BCD)
UNPK -(Ax), -(Ay), #<adjustment>
UNPK Dx, Dy, #<adjustment>
Description: Places the two BCD digits in the source operand
byte into the lower nibbles of two bytes, and places zero
bits in the upper nibbles of both bytes. Adds the adjustment
value to this unpacked value. Condition codes are not altered.
When both operands are data registers, the instruciton
unpacks the source register contents, adds the extension
word, and places the result in the destination register.
The high word of the distination register is unaffected.
When the specified addressing mode is predecrement, the
instruction extracts two BCD digits from a byte at the source
address. After unpacking the digits and adding the adjustment
word, the instruction writes the two bytes to the destination