Embedded Systems Design Europe - November 2007 - (Page 15) microcontrollers Through software, an MCU’s features can come to the forefront with minimal design tradeoffs. Unleash the power of flexible I/O BY GAURANG KAVAIYA pin mapping F eature creep and a tendency to maximize functionality within a compact microcontroller (MCU) often create problems for embedded system designers. Did you ever run into a situation where the application demanded multiple universal asynchronous receiver transmitters (UARTs), more than one serial peripheral interface (SPI) channel, and a few I/O pins? You zeroed in on a low pin-count MCU with the feature set you were looking for, only to later realize that everything about this design looked great until you started working on the schematic. Then you found out that one of the UART’s pins was multiplexed (two functions on same pin) with another peripheral you were trying to use in the application. If you’ve ever encountered this situation, you’re not alone. The use of multiple serial channels is just one example. You’ll find many design examples where two hardware peripheral features you need are actually mutually exclusive features, due to I/O pin multiplexing on the MCU. All MCUs have their I/O pin-outs defined by the chip makers. These MCUs feature multiple functions multiplexed www.embedded.com/europe | embedded systems design europe | NOVEMBER – DECEMBER 2007 15 015-016-017-018-019_ESDE.indd 15 6/11/07 13:14:27 http://www.embedded.com/europe
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