Saturday, 20 July 2013


BCD (Binary Coded Decimal)

·         It represents 0 to 9 digits.
·         4-bits binary = 1-bit BCD.
·         Invalid BCD numbers are 1010, 1011, 1100, 1101, 1110 and 1111.

   Decimal Digit BCD

   0          1         2          3          4          5          6          7          8          9         (decimal number)
0000   0001   0010   0011   0100    0101   0110   0111   1000   1001      (BCD code)

  Convert BCD code into Decimal number

(10000110)2
Step 1: break the given number in 4, 4-bit.
1000   0110
Step 2: convert these 4-bit into their respective decimal numbers.
1000   0110
  8           6
Given BCD is (86)10 in Decimal number.


  Convert Decimal  number into BCD code

(453)10
Step 1: convert each decimal digit into 4-bit of binary number.
   4           5          3
0100    0101    0011
Step 2: join these binary digits.
(010001010011)2

 BCD Addition

   23      →   00100011        
+15      →    00010101
   38      →   00111000

  BCD Subtraction

86-41=?
41 → 01000001 → 2’s compliment → 10111111 → -41
  86 →   10000110
-41 →   10111111
 451 01000101
Here  left most 1 is discarded.

Note:


If answer of addition or subtraction of BCD numbers is invalid, then add +6 or -6 respectively to their answers to get valid answer.
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