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: "D Poinsett"
Subject: Re: To C or not to C
Date: Sun, 5 Jan 2003 12:58:22 -0500
Organization: Posted via Supernews, http://www.supernews.com
References: <firstname.lastname@example.org> <email@example.com> <firstname.lastname@example.org>
X-Newsreader: Microsoft Outlook Express 6.00.2800.1106
Good question. You are right; it's still read-modify-write. But in the
HC11/H12 there are machine instructions that do this all in one instruction
cycle thus interrupts or other hardware-sourced changes are locked out until
the instruction completes. This is in contrast to read-modify-write routines
where each operation is performed with separate instructions. Sorry I was
not more clear.
"Frank Bemelman" wrote in message
> "D Poinsett" schreef in bericht
> > Hi Nico,
> > Good point.
> > However, bit twiddling/testing macros vary depending on the target
> > and the way the macro is written. A common method is to read a byte,
> > some AND or OR instruction, and possibly write the result back. For
> > processors like the HC11/HC12, multiple bits can be set/reset/tested in
> > instruction eliminating the possibility that changes may have occurred
> > that register/memory location (due to an interrupt or hardware, for
> > example), changes that could be disturbed if the result of the macro bit
> > twiddling/testing is written back to that location after the change
> > occurred.
> Also for memory locations? How can that work other than
> a read-modify-write scheme?
> Frank Bemelman
> (remove 'x' & .invalid when sending email)
Go Back To The Cyber-Spy.Com
Usenet Web Archive Index Of
The sci.electronics.design Newsgroup