Difference between IDE and SCSI ??

Les hlhowell at pacbell.net
Mon Feb 4 18:06:06 UTC 2008


On Mon, 2008-02-04 at 17:00 +0900, John Summerfield wrote:
> Alan Cox wrote:
> > On Sun, 03 Feb 2008 13:54:26 +1030
> > Tim <ignored_mailbox at yahoo.com.au> wrote:
> > 
> >> On Sat, 2008-02-02 at 11:57 -0800, Les wrote:
> >>> SCSI is a serial system, or at least it can be.
> >> Pardon?  Usually, when one has a data bus for several parallel data
> >> lines at once, one refers to it as parallel.
> >>
> >> Serial - one data line, that sends bits sequentially.
> >> Parallel - several data lines, that send bits simultaneously.
> > 
> > Of course its never that simple. Most "serial" busses are actually
> > multiple wires which send information in parallel..
> 
> More likely
> txdata
> rxdata
> Maybe a pair for the other direction (eg RS0232C)
> Ground
> 
> For a modern cable that has fair throughput, view your ethernet cable:
> http://www.ertyu.org/steven_nikkel/ethernetcables.html

Note that RS-232 is a complete bus standard, and although many
implementations are not complete, lacking some of the handshaking and
enough drive to actually meet the specification (a bus buffer is often
used instead of a line driver chip), it contains several signals in
parallel to and operating synchronously with the data.   Some of the
signals indicate the line termination and equipment status.  The poor
implementation of rs232 is what lends people to think of it as a serial
port rather than a serial bus.

Look at this simplified explanation of the RS232 signals:
http://www.camiresearch.com/Data_Com_Basics/RS232_standard.html

Regards,
Les H




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