From PICLIST@MITVMA.MIT.EDU Fri Nov 15 07:24:03 2002 Received: from cherry.ease.lsoft.com [209.119.0.109] by dpmail10.doteasy.com with ESMTP (SMTPD32-7.13) id A19317FD00A6; Fri, 15 Nov 2002 07:24:03 -0800 Received: from PEAR.EASE.LSOFT.COM (209.119.0.19) by cherry.ease.lsoft.com (LSMTP for Digital Unix v1.1b) with SMTP id <21.007DC966@cherry.ease.lsoft.com>; Fri, 15 Nov 2002 10:09:57 -0500 Received: from MITVMA.MIT.EDU by MITVMA.MIT.EDU (LISTSERV-TCP/IP release 1.8d) with spool id 3545 for PICLIST@MITVMA.MIT.EDU; Fri, 15 Nov 2002 09:58:36 -0500 Received: from MITVMA (NJE origin SMTP@MITVMA) by MITVMA.MIT.EDU (LMail V1.2d/1.8d) with BSMTP id 1335; Fri, 15 Nov 2002 09:57:20 -0500 Received: from kona.reonbroadband.com [66.51.65.3] by mitvma.mit.edu (IBM VM SMTP Level 320) via TCP with ESMTP ; Fri, 15 Nov 2002 09:57:19 EST X-Comment: mitvma.mit.edu: Mail was sent by kona.reonbroadband.com Received: from mail.embedinc.com (86-66-51-66.reonbroadband.com [66.51.66.86]) by kona.reonbroadband.com (8.9.3/8.8.7) with SMTP id JAA09363 for ; Fri, 15 Nov 2002 09:57:23 -0500 Received: from 192.168.0.3 (main) by mail.embedinc.com ; 2002 NOV 15 09:55:41 EST References: <004b01c28c23$51b8ba40$6501a8c0@potshe01.pa.comcast.net> <006401c28ca1$b0a4aa40$6501a8c0@potshe01.pa.comcast.net> <009101c28caa$1eec0b30$0300a8c0@main> <007701c28cb1$6e1eaf80$6501a8c0@potshe01.pa.comcast.net> MIME-Version: 1.0 Content-Type: text/plain; charset="iso-8859-1" Content-Transfer-Encoding: 7bit X-Priority: 3 X-MSMail-Priority: Normal X-Mailer: Microsoft Outlook Express 6.00.2600.0000 X-MimeOLE: Produced By Microsoft MimeOLE V6.00.2600.0000 Message-ID: <001f01c28cb7$5f128bf0$0300a8c0@main> Date: Fri, 15 Nov 2002 09:57:51 -0500 Reply-To: pic microcontroller discussion list Sender: pic microcontroller discussion list From: Olin Lathrop Subject: Re: [PIC]: 16F627 brown out? question To: PICLIST@MITVMA.MIT.EDU X-RCPT-TO: Status: R X-UIDL: 277600680 X-Evolution-Source: pop://mailinglist%40farcite.net@mail.farcite.net/ X-Evolution: 0000077b-0000 > LP, 32.768Khz, 3.015V > The oscillator is alive, though execution has ceased based upon observance > of the IO pins. > > ... > > Here is the normal course of events (which I intend to get rid of, but must > live with at the moment). Processor powers up (0 to 3V in under 150uS). > Processor reads operating parameters from internal EPROM. Processor takes > 150ms scanning an IO port for signal and giving commands to an amplifier. > If no signals are found it sends an IO pin high to initiate power shut down. > The power supply is terminated, using an RC network to re-apply power 300 ms > later. Power supply goes all the way down to 0, and all the way back to 3V. > This repeats indefinitely. As an experiment, try making the 300mS time much larger so that the processor is held at 0V power longer. Perhaps 300mS is not enough to drain some internal capacitance in the reset logic. Also note that the crystal oscillator takes a while (1000 cycles if I remember right) before the chip is allowed to run. This is independent of the powerup timer, and would be over 30mS in your case. The 16F627 should draw under 10uA with a 32KHz crystal. Is it really worth it to shut down the processor completely for such short periods of time? You may be causing more effective supply current draw by charging and discharging capacitances in the system every time the supply goes up and down. For example, to get 10uA effective average current drain only requires a 1.7uF capacitor to be charged to 3V twice per second. ***************************************************************** Embed Inc, embedded system specialists in Littleton Massachusetts (978) 742-9014, http://www.embedinc.com -- http://www.piclist.com hint: The PICList is archived three different ways. See http://www.piclist.com/#archives for details.