80C186EC/80C188EC Microprocessor User's Manual

OVERVIEW OF THE 80C186 FAMILY ARCHITECTURE
Table 2-5 shows the interpretations of various bit patterns according to number type. Binary numbers
can be 8 or 16 bits long. Decimal numbers are stored in bytes, two digits per byte for packed
decimal and one digit per byte for unpacked decimal. The processor assumes that the operands in
arithmetic instructions contain data that represents valid numbers for that instruction. Invalid data
may produce unpredictable results. The Execution Unit analyzes the results of arithmetic instructions
and adjusts status flags accordingly.
Table 2-4. Arithmetic Instructions
Addition
ADD Add byte or word
ADC Add byte or word with carry
INC Increment byte or word by 1
AAA ASCII adjust for addition
DAA Decimal adjust for addition
Subtraction
SUB Subtract byte or word
SBB Subtract byte or word with borrow
DEC Decrement byte or word by 1
NEG Negate byte or word
CMP Compare byte or word
AAS ASCII adjust for subtraction
DAS Decimal adjust for subtraction
Multiplication
MUL
IMUL
AAM
Multiply byte or word unsigned
Integer multiply byte or word
ASCII adjust for multiplication
Division
DIV
IDIV
AAD
CBW
CWD
Divide byte or word unsigned
Integer divide byte or word
ASCII adjust for division
Convert byte to word
Convert word to double-word
2-20