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From: | Zehao Chang |
Subject: | [avr-chat] Mega16L with SPI Flash communication problem. |
Date: | Tue, 28 Feb 2006 12:25:48 -0800 |
When I do a write instruction, the serial output of the flash stays low, which is fine. But when I do a read instruction, the serial output pulses high and then exhibits capacitive decay, and does not look like a digital signal. Here's what the output of the flash chip look like when there is no load (not connected to microprocessor). It seems to go high for the duration of the chip select signal and then decays exponentially:
http://www.zehao.com/temp/spiflash_miso.jpg Here's the corresponding chip select signal (0 means chip is selected): http://www.zehao.com/temp/spiflash_select.jpgIf I connect the output pin to the AVR, it becomes a flat ~2V signal. I've tried 3 different chips and they all do the same thing. Can anyone give me an advice or hazard a guess as to why this is happening?
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