Programmier-Modus-Auswahl mit JTAG Schaltungen

A technique to provide higher system performance by increasing amount of data that may be transferred in parallel is to increase the number of external pins available for the input and output of user data (user I/O). Specifically, a technique is to reduce the number of dedicated pins, leaving more external pins available for user I/O. The dedicated pins used to implement a function such as the JTAG boundary scan architecture may be also be used to provide other functionality, such as to select the programming modes. In a specific embodiment, a JTAG instruction code that is not already used for a JTAG boundary scan instruction stored in an instruction register (220) may be used to replace the programming mode select pins (252) in a programmable logic device (PLD).