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Subject: 
Re: BCD
Newsgroups: 
lugnet.robotics.handyboard
Date: 
Wed, 2 Apr 1997 20:19:55 GMT
Original-From: 
Rajesh Gottlieb <RAJESHG@CCWF.CCspamcake.UTEXAS.EDU>
Viewed: 
1634 times
  
Does anyone know the details of how a BCD number is stored?
I'm unsure as to what a "half-carry" is in HC11 CCR.
It would be great if someone can provide a little example.  :)

As far as BSD goes; every decimal digit is represented by four binary
digits:

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

so that a number like 3725 would be represented by
0011 0111 0010 0101

I've never heard the term "half-carry" before, but it might be related to
the fact that you can't add two BCD's as if they were ordinary binary
numbers. For example if you were to perform to operation 3725 + 6 you
would get

  0011 0111 0010 0101
+ 0000 0000 0000 0110
_____________________
  0011 0111 0011 0001

Hope this helps

Rajesh



Message has 1 Reply:
  Re: BCD
 
Yeah, it helps alot. Thanks. I guess the half-cary is for adding to the next significant 4 bit word. And the current word, including overflow, is then subtracted by ten (1010), if the half-carry is flaged, to yield the proper BCD word. Is this what (...) (27 years ago, 3-Apr-97, to lugnet.robotics.handyboard)

Message is in Reply To:
  BCD
 
Does anyone know the details of how a BCD number is stored? I'm unsure as to what a "half-carry" is in HC11 CCR. It would be great if someone can provide a little example. :) ---...--- ericson mar Master of Engineering Candidate Project: Mobile (...) (27 years ago, 2-Apr-97, to lugnet.robotics.handyboard)

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