Received: by 10.66.85.137 with SMTP id h9mr4374884paz.16.1349728580923; Mon, 08 Oct 2012 13:36:20 -0700 (PDT) Path: t10ni23657341pbh.0!nntp.google.com!news.glorb.com!eternal-september.org!feeder.eternal-september.org!mx04.eternal-september.org!.POSTED!not-for-mail From: rickman Newsgroups: comp.lang.forth Subject: Re: GA144 polyForth Date: Mon, 08 Oct 2012 16:36:15 -0400 Organization: A noiseless patient Spider Lines: 36 Message-ID: References: <32e7fd8d-7494-4010-a9d5-d9673a3df831@googlegroups.com> <7xzk409lb7.fsf@ruckus.brouhaha.com> <4fdeaae3-ea51-4a69-84fd-a163baab7c1d@googlegroups.com> <4117939.2SUbERvFEv@sunwukong.fritz.box> Mime-Version: 1.0 Injection-Date: Mon, 8 Oct 2012 20:36:20 +0000 (UTC) Injection-Info: mx04.eternal-september.org; posting-host="322a3bf5484cfc4b8b01205bf755aad6"; logging-data="13339"; mail-complaints-to="ab...@eternal-september.org"; posting-account="U2FsdGVkX1/SybeIoisIRyI7tOUtqo7L" User-Agent: Mozilla/5.0 (Windows NT 6.0; rv:12.0) Gecko/20120428 Thunderbird/12.0.1 In-Reply-To: <4117939.2SUbERvFEv@sunwukong.fritz.box> Cancel-Lock: sha1:T1p5U3UNzoU/B2cdpm7rsB45wW8= Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit On 10/8/2012 2:10 PM, Bernd Paysan wrote: > rickman wrote: >> The async processor goes to sleep until an input triggers it. So why >> not use a clock for that input? Then the GA144 core could utilize >> very little power just waiting. > > You wrote it above: Chuck stops the clock, there is no clock to be used > during sleeping time. > > You can stop your clock in a serial interface after the stop bit, > waiting for the next start bit (that's the purpose of the start bit, to > provide a transition). You have to keep it running until the stop bit > arrives. > I'm not sure what clock you are talking about. I'm talking about a clock that is used to measure the period of the async bits, a requirement in an async protocol. The UART node can be stopped waiting for a transition on the input. When the start bit transition happens on the async input the UART node sends a message to the timer node which counts external timing clock edges to measure time. Meanwhile both nodes stop. The timer node waits for clock edges and the UART node waits for a message from the timer node as well as further edges from the async input. If the async input transitions first the bit is considered noise and the UART node starts over. If the timer message arrives first this marks the middle of the start bit. On subsequent timer messages the UART node reads the async input to get data and overhead bits. I believe Chuck does not like to use an external clock because it is "extra" hardware and dissipates power. But a 5 mW node is not exactly a "light" footprint to do nothing other than mark time. I prefer the external clock. Rick