1.2.2 Boundary scan test vectors
If you use the JTAG boundary scan test methodology to apply production test vectors, you might want to
have independent external access to each Test Access Port (TAP) controller. This avoids the requirement
to merge test vectors for more than one block in the device.
One solution to this is to adopt a hybrid approach, using a pin on the package that switches elements of
the device into a test mode. You can use this to break the internal daisy chaining of TDO and TDI
signals, and to multiplex out independent JTAG ports on pins that are used for another purpose during
normal operation.
1 ARM
®
DSTREAM-ST system design guidelines
1.2 Working with Application-Specific Integrated Circuits (ASIC) or System-on-Chips (SoC)
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