Pin Mappings

When using XJTAG products, the pin mapping of the JTAG controller is configurable. Apart from some fixed-purpose Ground pins, all other pins can be configured as any of the JTAG signals, and if not being used for a JTAG signal can be used as a programmable I/O (PIO) pin.

XJTAG supports multiple pin mappings in a project, which allows a single project to be used and run with different XJLink types, without needing to edit the project.

The configuration of the pins on the JTAG controller can be exported as a Pin Mapping file (*.xjpm). This file format can then be imported into other projects. It also allows custom Test Reset Sequences to be defined, which are used to make sure the devices in the circuit are set up to respond to JTAG instructions.

Pin mappings are mostly created, imported or exported using XJDeveloper or the JTAG Chain Debugger application, but pin mappings can also be created or imported into XJAnalyser.

Programmable I/O (PIO) Pins

A PIO pin on an XJLink is a pin which can be used as either an input or an output during testing. It is not part of a JTAG connection but can be used to control or read other signals.

PIO pins can be used during the Test Reset Sequence, for example to drive reset pins or to turn on power supplies. They can also be used to drive and read signals during XJEase testing, either by explicitly driving/reading the PIO pin, or using normal XJEase SET statements to set/read nets which the PIO pin is attached to. This requires the connection between the XJLink and the UUT to be defined.

PIO pins are also used during the connection test. The connection test treats them very much like additional JTAG-controlled pins on their nets. Note however that if any connections are defined between the XJLink and the UUT, all PIO pins will be used in the connection test, so you should make sure that all connections are defined if any of them are.