1. Arithmetic Instructions and Programs

2. Outlines Range of numbers in 8051 unsigned data Range of numbers in 8051 unsigned data Addition & subtraction instructions for unsigned data Addition & subtraction instructions for unsigned data BCD system of data representation BCD system of data representation Packed and unpacked BCD data Packed and unpacked BCD data Addition & subtraction on BCD data Addition & subtraction on BCD data Range of numbers in 8051 signed data Range of numbers in 8051 signed data Signed data arithmetic instructions Signed data arithmetic instructions Carry & overflow problems & corrections Carry & overflow problems & corrections

3. Addition of Unsigned Numbers ADDA, source; A = A + source ADDA, source; A = A + source

5. Addition of Individual Bytes

6. ADDC & Addition of 16-bit Numbers 1 3CE7 3B8D 7874 +

7. BCD Number System Unpacked BCD: 1 byte Unpacked BCD: 1 byte Packed BCD: 4 bits Packed BCD: 4 bits

8. Adding BCD Numbers & DA Instruction MOVA,#17H ADDA,#28H MOVA,#47H;A=47H first BCD operandMOVB,#25H;B=25 second BCD operand ADDA,B;hex (binary) addition (A=6CH) DAA;adjust for BCD addition (A=72H) HEXBCD 290010 1001 +18 +0001 1000 +18 +0001 1000 410100 0001AC=1 + 6 + 0110 + 6 + 0110 470100 0111

9. Example

10. Subtraction of Unsigned Numbers SUBBA, source; A = A – source – CY SUBBA, source; A = A – source – CY SUBB when CY = 0 SUBB when CY = 0 Take 2 ’ s complement of subtraend (source)Take 2 ’ s complement of subtraend (source) Add it to minuendAdd it to minuend Invert carryInvert carry

11. Example (Positive Result)

12. Example (Negative Result)

13. SUBB When CY = 1 For multibyte numbers For multibyte numbers

14. Multiplication of Unsigned Numbers MULAB; A  B, place 16-bit result in B and A MULAB; A  B, place 16-bit result in B and A MOVA,#25H;load 25H to reg. A MOVB,#65H;load 65H in reg. B MULAB;25H * 65H = E99 where ;B = 0EH and A = 99H Table 6-1:Unsigned Multiplication Summary (MUL AB) Multiplication Operand 1 Operand 2 Result byte  byte AB A=low byte, B=high byte

15. Division of Unsigned Numbers DIVAB; divide A by B DIVAB; divide A by B MOVA,#95H;load 95 into A MOVB,#10H;load 10 into B DIVAB;now A = 09 (quotient) and ;B = 05 (remainder) Table 6-2:Unsigned Division Summary (DIV AB) DivisionNumerator Denominat or Quotient Remainde r byte / byte ABAB

16. Example ( 1 of 2 )

17. Example ( 2 of 2 )

18. Signed 8-bit Operands Covert to 2 ’ s complement Covert to 2 ’ s complement Write magnitude of number in 8-bit binary (no sign)Write magnitude of number in 8-bit binary (no sign) Invert each bitInvert each bit Add 1 to itAdd 1 to it

19. Example

20. Example

21. Example

22. Byte-sized Signed Numbers Ranges DecimalBinaryHex -1281000 000080 -1271000 000181 -1261000 001082 …. ………….. -21111 1110FE -11111 1111FF 00000 000000 00000 000000 +10000 000101 +20000 001002 ……………... +1270111 11117F

23. Overflow in Signed Number Operations

24. When Is the OV Flag Set? Either: there is a carry from D6 to D7 but no carry out of D7 (CY = 0) Either: there is a carry from D6 to D7 but no carry out of D7 (CY = 0) Or: there is a carry from D7 out (CY = 1) but no carry from D6 to D7 Or: there is a carry from D7 out (CY = 1) but no carry from D6 to D7

25. Example

26. Example

27. Example