Non-JTAG Devices

Now that you have provided information about the JTAG devices, XJDeveloper has used information extracted from the netlist to generate a list of devices which it needs further information about in order to get the best test coverage.

These devices are listed on the Categorise Devices screen.

The Uncategorised Devices panel groups the uncategorised devices into suggested categories, based on:

• The device references
• Information extracted from the BOM file
• The identified power and ground nets

Each of the devices shown in the panel needs to be placed in one of the following categories:

Passive Devices

The Passive Devices category in XJDeveloper is for:

• Devices that join nets, such as series resistors and jumpers
• Pull-up and pull-down resistors
• Coupling capacitors
• Termination resistors

Logic Devices

Logic Devices are devices whose function can be described with a truth table, such as a logic gate or buffer. Where their connections to JTAG-enabled devices allow, these devices will be tested automatically as part of the Connection Test.

Like Passive devices, these devices will extend XJDeveloper's knowledge of areas of the circuit that are accessible from the JTAG devices.

Test Devices

There are two reasons why a device should be categorised as a Test Device:

• The connections of the device are going to be tested using its functionality (e.g. LEDs).
• The device drives some or all of the nets to which it is connected, such as the data nets connected to the memory devices. Any such outputs must either be stopped from driving or be described to the system in order to stop XJTAG from driving the nets when running the Connection Test.

Each device in this category will have a corresponding XJEase device file. The XJEase tests that are required for this tutorial, along with tests for several thousand other devices, are available in the installed XJEase library.

Ignored Devices

Ignored Devices are devices that will not drive any of the nets to which they are connected, and that cannot be controlled in such a way as to get additional test coverage outside the Connection Test. Connectors and capacitors are typically Ignored devices.

Unfitted Devices

Unfitted Devices are devices that are in the netlist but not physically fitted to the board. Categorising a device as Unfitted will remove its pins from the test coverage statistics.

Excluded Devices

The final option is the Excluded Devices category. We won't be categorising any devices as Excluded in this tutorial, but more information on what type of devices should be categorised in this way can be found here.

If you are unsure how to categorise a device, leave it uncategorised. This will mean that connections to it are left undriven by the Connection Test. Do not categorise devices as Ignored if you are uncertain that this is the appropriate category for them.

The table below shows a summary of how the devices on the XJDemo board will be categorised.

Device References	Category	Reason
R9, R10, R16, R17, R32-R35, R38, R39, R41, R42, R47, R75, RN1	Passive	These resistors are pull-up / pull-down resistors, which can be verified by the Connection Test.
R1-R4, R8, R11-R13	Passive	These resistors are pull resistors on the JTAG TAP signals.
R6, R14, R19, R21, R40, R44-R46, R48-R64	Passive	These resistors are series resistors that connect nets together and allow other components to be identified and tested.
FB1-FB5	Passive	These ferrite beads connect power nets together. They have already been categorised by using the Links... function on the Power/Ground Nets screen.
FCJ1	Passive	The fault-creation jumpers. By default (as marked on the PCB) some of the pins on FCJ1 are linked together; these connections need to be described.
U8-U10, U15	Logic	By describing the logical operation of these devices, both the connection test and XJEase tests will be able to find faults on a greater proportion of the board.
D1-D9	Test	These are LEDs, which we will test by turning them on and off.
U3-U7, U11, U12, X1	Test	These non-JTAG devices will be tested with XJEase device files.
SW1	Test	This push-button switch will use a very simple XJEase script to check that it is correctly connected to the board.
P1, P3, JP1	Ignored	These are external connectors. P1 is the JTAG connector, and P3 is the Digital IO connector. Neither of these connectors will be driving the nets connected to them so they can safely be ignored. JP1 can be used to actively control the nTRST pin on the MCU – by default there is no jumper fitted so this header can also be ignored.
C3-C5	Ignored	These capacitors are on the I2C bus and MCU reset signals – they stop interference caused by crosstalk from the JTAG signals on the 20-way ribbon cable. They do not drive these nets and cannot be tested so they can safely be ignored.
R37, R77, R79, R81, R84, C11, C12, LK1, JP2, all test points and fiducials	Unfitted	The resistors, capacitors and jumpers are included in the design but are not fitted to the board in production. The test points and fiducials are part of the PCB and are not actively 'fitted to the board'. If they were not marked as unfitted they would skew the test coverage statistics.

In the next stage of this tutorial you will start categorising these devices. Not all of the devices will appear to need categorisation at first, but as you categorise devices, more will become accessible from JTAG and will therefore appear in XJDeveloper's list of uncategorised devices.