X-Authentication-Warning: delorie.com: mail set sender to geda-user-bounces using -f X-Recipient: geda-user AT delorie DOT com Content-Type: text/plain; charset=iso-8859-1 Mime-Version: 1.0 (Apple Message framework v1283) Subject: Re: [geda-user] T flip-flop From: Roger Williams In-Reply-To: <201308101615.39595.ad252@freeelectron.net> Date: Sat, 10 Aug 2013 16:51:13 -0400 Content-Transfer-Encoding: 7bit Message-Id: References: <201308101615 DOT 39595 DOT ad252 AT freeelectron DOT net> To: geda-user AT delorie DOT com X-Mailer: Apple Mail (2.1283) X-AntiAbuse: This header was added to track abuse, please include it with any abuse report X-AntiAbuse: Primary Hostname - server.qux.com X-AntiAbuse: Original Domain - delorie.com X-AntiAbuse: Originator/Caller UID/GID - [47 12] / [47 12] X-AntiAbuse: Sender Address Domain - qux.com X-Get-Message-Sender-Via: server.qux.com: authenticated_id: raw AT qux DOT org X-Source: X-Source-Args: X-Source-Dir: Reply-To: geda-user AT delorie DOT com Errors-To: nobody AT delorie DOT com X-Mailing-List: geda-user AT delorie DOT com X-Unsubscribes-To: listserv AT delorie DOT com Precedence: bulk Hi, Al, This is the point where I turn to a microcontroller. It's flexible, by far the cheapest solution ($1-2), and the code to debounce pushbuttons and toggle outputs is pretty trivial, even in assembly language. Unfortunately, as you've discovered, integrated T flops are pretty rare (I only know of ECL devices), so you need to construct them with JK flops. But a JK flip-flop with an independent clock takes a lot of pins, so you need a lot of packages. If you needed speed, a CPLD would be the logical choice, but it's hard to imagine that being a criterion for a pushbutton interface. -- Roger Williams Chief Technical Officer, Qux Corporation 245 Russell Street, Hadley, MA 01035, USA Tel +1 508 287-1420 * Fax +1 508 302-0230 On 2013/08/10, at 16:15, al davis wrote: > I have a need for a "T" flip-flop ...... to map a momentary > pushbutton to on or off. > > The application needs 20 of them in a tight space, preferably > arranged in 4 groups of 5. > > Looking for suggestions of a chip to do this, with a minimum > package count and space requirement. > > Wishing for a "hex T flip-flop", but I can't find it. > > The best I can find seems to be a dual JK flipflop. That's 10 > packages. > > I found a quad JK flipflop, but they share a common clock so > that doesn't work for this application. > > I can do better in cost and space with discretes. > > ideas???