RE: [68300]
2002-05-06 by Melear Charles-rdph40
Tena, I need a little more information about some of your hardware but I can make some relatively safe guesses. First, if you are doing any type of bus arbitration on the MC68332, you will have CS0/BR, CS1/BG and CS2/BGA configured as BR, BG and BGA. I am further going to assume that you only have something tied to BR but NOT BGA. Well, I guess that BG is involved there somewhere but it is an output. What might be happening is that you DO NOT have anything connected to BGA (Bus Grant Acknowledge). This is a really dangerous pin in that if it floats low, the bus will get tri-stated. That's right. The bus will tri-state even if BR is high (inactive). Make sure you have a pull-up on BGA. This may solve your problem. Bye the bye, don't even bother to mention the "non-existant" internal pull-ups. There are none and just because it worked before, it may not work now. There is only one mask set of the MC68332 manufactured right now and I believe that it is J30C. This is one of our best mask sets. However, it runs in a wafer line where the device thresholds allow input pins to drift around a little easier than before. (Use a pull up and be safe.) Regards, Charlie
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-----Original Message----- From: Tena Britt [mailto:tbritt@...] Sent: Saturday, May 04, 2002 11:33 AM To: 68300@yahoogroups.com Cc: Dennis Belt; Dave Peterson Subject: [68300] We have seen rare instances in our application when on a read of a flash memory part the part outputs 0xffff. The part is not corrupt, a subsequent read will produce the correct data. We have caught several of the incidents on a logic analyzer and have found that they always occur after a bus arbitration cycle. The 68332 tri-states the address lines, the pull-ups start to pull them up, then the address lines are driven with a valid address and the flash is read. The flash is used with the chip select always pulled, and WE and OE are toggled. Does anyone know of a problem with flash when the CS is pulled and WE and OE are disabled, if the address lines are at invalid levels? Also, is there a way to minimize the time between when the 68332 stops driving the address lines, and when it issues a bus grant? (BG) *** The information in this e-mail is confidential and intended solely for the individual or entity to whom it is addressed. If you have received this e-mail in error please notify the sender by return e-mail, delete this e-mail, and refrain from any disclosure or action based on the information. **** --------------------------------------------------- To unsubscribe from this group, send an email to: 68300-unsubscribe@yahoogroups.com To learn more about Motorola Microcontrollers, please visit http://www.motorola.com/mcu Your use of Yahoo! Groups is subject to http://docs.yahoo.com/info/terms/