Multiplexing JTAG Interface Pins on MAXQ Microcontrollers
Often in embedded applications, every last port pin on a microcontroller is needed, leaving none to spare. Most MAXQ microcontrollers with rewriteable internal program memory (such as flash memory or EEPROM) support a standardized JTAG/TAP interface (also known as the debug port) which is used by an external host to access in-circuit debugging or in-circuit programming (bootloader) functions. The pins which make up this interface are usually multiplexed with standard GPIO port-pin functions, which means that they are potentially available to the application instead of going to waste once the development phase is complete. This application note discusses methods of reusing these pins for general application purposes and presents considerations to keep in mind when doing so.
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