The Cyber-Spy.Com Usenet Archive Feeds Directly
From The Open And Publicly Available Newsgroup
This Group And Thousands Of Others Are Available
On Most IS NNTP News Servers On Port 119.
Cyber-Spy.Com Is NOT Responsible For Any Topic,
Opinions Or Content Posted To This Or Any Other
Newsgroup. This Web Archive Of The Newsgroup And
Posts Are For Informational Purposes Only.
From: Fred Bloggs
User-Agent: Mozilla/5.0 (Windows; U; Win 9x 4.90; en-US; rv:1.0.1) Gecko/20020823 Netscape/7.0
X-Accept-Language: en-us, en
Subject: Re: ? Binary to BCD conversion chip ?
References: <email@example.com> <3DE5D8B5.EF8930F3@scazon.com> <firstname.lastname@example.org>
Date: Thu, 28 Nov 2002 17:06:07 GMT
NNTP-Posting-Date: Thu, 28 Nov 2002 09:06:07 PST
Organization: EarthLink Inc. -- http://www.EarthLink.net
Tony Williams wrote:
> In article <3DE5D8B5.EF8930F3@scazon.com>,
> Paul Burke wrote:
>>There is an algorithmic way to do the conversion on an incoming stream
>>of data. All I can remember about it was that it was in an old
>>programmable logic applications book (over 15 years ago)- perhaps MMI? A
>>colleague implemented it in software on a 6809 and all I can say is it
>>worked, and saved a few vital bytes compared with divides or repeated
>>subtraction. Took an age though.
> I think there's an example in a PIC app note.
It's a bit-instruction intensive add-3 algorithm that requires shifting
of the BCD result nibbles. It iteratively multiplies the BCD nibbles by
shift lefts but before this is done each nibble must have 3 added to it
if >5- a simple variant of the add-6 decimal adjust.
There was a 74XXX MSI that performed the conversion nibble-wise
combinatorially- but the number of chips required grew as some
ridiculous thing like 10^(nibbles) or something unusable like that.
If the number of digits is large then the answer is a uproc. If it's
small like 2-4 digits then a CPLD using a simple counter algorithm is
far more useful than EPROM. For an 8-bit binary to 12-bit BCD, this is
only 20 bits, and say 7 bits for a BCD-7-segment encoder for subtotal 27
bits, leaves 9 macrocells open for display mux'ing, input latching, and
other tasks in the low-end Xilinx XC9536-15PC44C from Xilinx at $3.30
unit quantity available from their website or DigiKey. The fitting and
design software is free- handles nearly any reasonable design entry
method, but the parallel port programming cable is a bit pricey at $95.
Go Back To The Cyber-Spy.Com
Usenet Web Archive Index Of
The sci.electronics.design Newsgroup