FILE: cherupakha.media.mit.edu:pub/6270/debugging/download-mode-info.txt DATE CREATED: Oct 17, 1993 -------------------- Return-Path: fredm@media.mit.edu Received: by media.mit.edu (5.57/DA1.0.4.amt) id AA03841; Sun, 17 Oct 93 09:32:51 -0400 Message-Id: <9310171332.AA03841@media.mit.edu> To: kwh@cs.brown.edu (Kwun Han) Cc: fredm@media.mit.edu, rv@cs.brown.edu, dulimart@cps.msu.edu, jbf1@midway.uchicago.edu Subject: Re: 6.270 problem In-Reply-To: Your message of "Sun, 17 Oct 93 06:05:36 EDT." <9310171005.AA15386@vegas.cs.brown.edu> Date: Sun, 17 Oct 93 09:32:50 -0400 From: "Fred G. Martin" X-Mts: smtp > I am one of the people who have problem with our 6.270 board. > When I turn on the board, the yellow LED (Tx) glows constantly. I > spent a night debugging it and I think I found the problem. I believe the debugging instructions that claim that the yellow light should flicker are incorrect. (As you may know, I didn't write the latest revisions to the doc's.) > I was looking at the timing between the reset pin and then > MODEA and MODEB pin, seems that when the reset pin goes high, MODEA is > HIGH and MODEB is LOW. From my 68HC11 manual, that sets the board to > a "Special Test" mode, and I think that is wrong. I think it should be > in "Special Bootstrap" mode (please tell me if I am wrong). My > observation is, the MODEA pin goes from LOW to HIGH about 300ms before > the RESET pin goes high. The way it should work as you observed. The board should reset into Special Test mode: this is the normal running mode (see the discussion about how the LCD works for an explanation). To get the board into Special Bootstrap (that is, "download mode"), you must hold down either the Choose or Escape button (I don't know which it is, sorry) and press reset. When the board comes out of reset, it will be in Bootstrap (with the yellow LED completely off.) > Therefore I predict that the delay circuitry > for MODEA is wrong (probably the capacitor is too small). I was > reading the 6.270 docs and it mentioned something about that. The 300 ms delay is caused by the Dallas DS1233 reset monitor chip and -not- an RC delay line as described in the board docs. This is the significant change from the 2.1x-2.20 boards to the 2.21 board. It seems that the new organizers have not taken the time to revise the technical discussion of how the board works. > However, it is an old doc and the circuit is a bit different from the > board I have (rev 2.21). I wonder if you can tell me where I can find > the latest doc so that I can fix the board?? Or do you have any > suggestions what I can do?? As I indicated, I believe your board is working. Try resetting with the Choose or Escape button held down, and see if the yellow lamp goes off. If so, you're in business. -Fred Return-Path: fredm@media.mit.edu Received: by media.mit.edu (5.57/DA1.0.4.amt) id AA07419; Sun, 17 Oct 93 12:03:36 -0400 Message-Id: <9310171603.AA07419@media.mit.edu> To: kwh@cs.brown.edu (Kwun Han) Cc: "Fred G. Martin" , jbf1@midway.uchicago.edu, dulimart@cps.msu.edu, rv@cs.brown.edu Subject: Re: 6.270 problem In-Reply-To: Your message of "Sun, 17 Oct 93 09:35:06 EDT." <9310171335.AA10370@tahoe.cs.brown.edu> Date: Sun, 17 Oct 93 12:03:35 -0400 From: "Fred G. Martin" X-Mts: smtp > "Fred G. Martin" writes: > >As I indicated, I believe your board is working. Try resetting with > >the Choose or Escape button held down, and see if the yellow lamp goes > >off. If so, you're in business. > > Fred, > > Yeah... I tried doing that, the yellow light did go off after > I hold down choose and reset, however, when I plugged in the serial > line, the yellow light goes back to lit. And the downloader complains > that it is not in download mode. any ideas?? OK, we're making progress. First, your board is probably OK. The fact that the yellow light goes out means (with very high certainty) that the 6811 is properly resetting into its bootstrap mode. Second. The most frequent cause of problems w/download is an improperly wired serial connection. When you plug your board into your computer, the green LED (serial receive) should turn on. If it does not, then it's almost guaranteed that your cable is wired improperly. (The only exception I know to this is when using Macs: the Mac serial output driver doesn't turn on until the software tells it to.) Try swapping the TxD and RxD wires on your cable. This is probably the problem. Then try again. You might want to have your board plugged in, with the green LED on, and then reset the board to download (yellow LED off). At this point, your board should be ready to perform the download sequence. Good luck. Let us know the results. -Fred